Aspects of the co ordination chemistry of some transition metals

ACICijOWLEDGEMEijT§

The author ia mo't grateful to Dr

J

.Fergusson for his \.l.Lu.au"'"" and encouragement., thank&

w·.

T. Robina on for hi$ help in the oryetallography seation.

Ph

en

dto

R

n: ...

cp

diphO$

diars

ear

Methyl (CH₃-)

Phenyl

(c

₆

a

₅-)

ethylenediamine (NH

2

-caf ..

ca

2- NH2)

diethyld:tthiocarbamato

I0

₂H

5)2Ncs ... 2)

alkyl or aryl group cyolopentadianyl (C

0

Hs)

a bidentate phosphine

a bidentate arsine

ABS.TRACT

The work reported in this thesis is divided into three parte .. Part A ia concerned with etudies on stable oomplexes of dinitrogen, and related lig-ands ~ Part B detail$ studies on the rhenium (V) oxo ... oomplex a~

₂

:Re001

₅

, and part C outlines general expert mental details ., ·

Part A.. Some reactions of the dinitrogen oomplex [Ru(NH₃)₅(N₂)] 01 2

have been investigated and the oXidation potential of the [Ru(NH

3)5(N2

)J

:"&+ ion in neutral conditions bas been found to be approximately •0.95 volts. The reactions have demonstrated that [Ru(NH

3)5(N2)

J

012 prepared using hydradne hydrate is impure,

the impurity is probably [ Ru(NH

3)5 (N2H4)

1

012• The dinitrogen

of purified

l

Ru(NH₃)

5 (N2) ] 012 has not yet been reduced in

aqueous conditions , oontJ;ary to a previous report.

The reactions of some ruthenium, oJilmlum ~ iddium and rhodium complexes with hydrazine hydrate and with metal reduotants

(e.g. Zn) in concentrated ammonia were investigated. A number of products including [M(NH

3)5 (N2)

J

2

_{+, [}

_M(mi

3)4 (N2)2

J

2_+,

lM(NH

3)5 (CO)]

z+

(M= Os, Ru)1 \Jr(NH₃)₄ (CO)Cl] :11+

and [Rb(NH

3)5H

J a+,

together with hydrazine containing produots,

belongs to the orthorhombic space group Pnma with a = 1351.5, b • 1046 ..

s,

o •

681 .. 5pm and ~ = 4~~ The cations on

crystallographic mirror planes and the interatomic distances within the cation are os-N

2 (1$4pm); N:N (l12pm) 11nd Os•NH3 (212.,.215pm).

The ruthenium complex (Ru(NH₃)₅(N

2) ] c12 was found to form solid

solution• with (NH₃)

5ol] Cl2 whioh are ilomorphou.a with the above osmium complex.

system for the ruthenium diniU'oqen complex. The enetgy of the \>(NN) absorption in the solid solutions is up to 50 om ... l lower than fot pure [Ru(NH₃)₅(N₂) 1

,

and

it

is suggested that this

intetaotions in the solid state.

also that the two metals; osmium iridium, form strong-er bonds to halide and amJm.OJrthl, than do

the

were studied in this section. This complex ion is reported being different from most rhenium (V) complexes which

study demonstrated that

hi9h paramagnetism reported preViously has been 1hown to due to th$ presence paramagnetic Os

1 lntroduotion

Nitrogen

Flxatton

Stable Dinitrogen Complexes · summary of Present Work

2 The Purity and Reaotlons of lRu(l{R

3)5(N2)] Xntroduot!on

Purification of [Ru(N:a

3)5(N2)

1

012 Reactions ExPerimental 1 1 8 17 012 21 22 27 31 of Metal ...

u.., ...

"'~""'., under Reducing Conditions

Introduot!on 34

Discussion (a) Compounds prepared 3 6

(b) Reactions 48

(c) Comparison Metal Ions 51

Experimental

lntroduotion

Collection and Reduction of Data Discussion

5 Solid Solutions Involving ( Ru(NH₃)

rage,.~o

6 0 Infrared Spectra of soma Ammine Complexes

Introduction

82

Results and Discussion Experimental

·'1 Discussion of Dinitrogen as a Ligand

PARTS The Rhenium (Y.) Complex ReOCl;-Introduction

Review of Ra (V)

SummarY' work in PreGent Study Re•ulta

Preparation of

cs

₂Re001

5 96

Properties of Cs2

102

PART 0 Expedmenta.i 106

6 1

s

9 10

u.

12 13

14

15

16

Properties of the Nitrogenase

Proteint

Bttuotura1 ·

on 'I:>initro;en

Complexes Propert!e$ the Products

from

the

reaction of

Properties ·of (Rh(NH

3)

1

Br2

.;) (00) Absorption Frequencies for Ru (U) and lr(Ul)

Oomplexel

Properties of {Os(NH

3) 5 (CO)] of (dto)₂ (OO)n

Reaction Products

Calculated

Reactions Metal.

Hydrogen

Atoms

Structure Factors

4

16

23

37

40

44

4'1

48

65

65

tnteratomio lllstanoes and Angles in (Os(NH

3) 5(N2)

J

012 66 Route""Mean""Square Amplitudes of Vibration of

Anisotropic Atoms

Changes in Solid Solution Unit Cell Sizes with Composition

66

26

( <

Low-frequency Infrared Spectra of

Rhenium (IV) and (V) Chloro-complexes

11

100

Number 1 2 3 4 5 6 7 8 9 10 11

Transition Metals which with Dinitrogen

Two Possible Modea of Dinitrogen Co .... ordination Reactions of Ruthenium Complexes with Hydrazine Infrared Spectrum of [Ru(NH₃)

5 (N2) ] ZnC14

infrared Spectrum of {Ru(NH₃) ₅ (co)

J

01₂

Infrared Spectrum of [ _{lr(NH3) 4} (CO) Cl) 01 2 Inftared Spectrum of oi$ [ Ru(NH₃)

4 (N2) 2] Bt2

Reaction. Sequence to

Infrared Spectrum of [Os(NH₃) ₅ (CO)) 01₂

6

a

15

18

22

31 38 42 45 46

12 Infrared Spectrum of the Product from the Reaction of 50 lOs(NH₃)_{5Cl) 012 with Mg/Hg}

in·

NH₃

13 Contents the lOs(NH₃)₅(N₂)] 01₂ Unit Cell

14 The Cation ( (NH

3) 5(N2)

J

Z+ 67

15 Variation of Force Constante with Bond Lengths for 68

N.,..N Systems

P~M!o

94

100

Introduotion lt{itroSJen fixat&on

One of the most important ptocet~~~ses for Ute, as we know it, is the biological :fixation of atmospheric dinitrogen.

It

been variously estimated 1 '2 that in the order of 100 to 1000 million toni of dinitrogen, of which man about one tenth, ate fixed annually on of dinitrogen fixation probably the main limitation agricultural production in many less developed countries 1• ln developed countries, biological fixation still accounts for about two thirds of the annually fixed dinitrogen.

The chemical problem, in increasing the amount of nonbiologioal dinitrogen, stability the

d:l.nitrogen

~

is

;~40

l<J'. mole""l(S),

but the chemical the high energy

(52 4 kl mole -l) 3 to ... ""''" K. the first bond ..

This the cotteeponding bond dis ...

sociation isoelectronio ion (2

k1

mole -

1)

3 acetylene molecule (252 kJ, mole "" 1) 3 and carbon monoxide molecule (298 kJ.mole- 1) 3 •

(A more ext.e:mn

Monoxide is shown in Table 1).

Propert_y Dinitrogeh* Carbon Monoxide*

Bond Dissociation

Energy 945 kJ/mole 1073 kJ/mole

Dissociation Energy Corres p. Double

Bond 421 kJ/mole 775 kJ/mole (3)

Difference 5 24 kJ/mole 298 kJ/mole (3)

lst Ionisation

Potential 15.51 volts 14 .1 volts

Bond Stretching

2330cm- 1 (125) 2160cm-1(112)

Frequency

Force Constand 2 2. 2xl 05dynes/cm(l25) 18. 6x1 05 dynes/ cm(ll2)

Bond length 108.9 pm (58) 112.8 pm (143)

Dipole Moment 0 esu O.llxlO -18 esu

2

Dinitrowen

before any reaction can oceur.

ttu:~tt';ll11Cfl'lllll $UOb

as

the

alkali "",..",. ... ""

1 bUt '~>A"''"'•""

The •n~~~>U'-'""'

by and Sm1th4,

1 • Interaction

3 • Interaction

4 •

various

methods

5 •

v.atton will be

... u ... !n all

au:l1tr,09E~n with metal

A few

orararu.e compounds

6 '1 as the

also

with but

resultinS1

formulation. Compounds which the d1nitrogen

t or

ion, of unknown

sulphur

bet!Ul nrnnn~

co•lve,nt1on~~~ dia=onium salt, w1U

not

further.

(1)

This high

of aD&Iotiil~

(2)

!n

Until

very :recel\ilY

un111:1lle ln th!flt

nVAI'"'H teaotiO;n (N

2

3

S!lzrm3)

PfO'OeSUB, but

in an

dtmttogen

fixation

dinttrogen

known

• The

100,000

,000

40,000

as non ... heme

Metall,lO

atoms

=

1:6

Stable 1 or 2

•

a mbctute two

""a«J,E!11.ltU'lnt!m

••llt'tr<~:~rf!'lt!:e14

r

Nb

Tc

Hf

T

FIGURE 1

_ a) Metals that act as fixation catalysts

{ 1

H

b) Metals that react with (Ar-N;) in model

reactions of Nitrogenase

atoms definitely to involved.

'(3)

to reproduce biological dinitrogen fixation

been investigated with a number of transition metal

'rhe significant findings

are:-(a) catalytic reduction of dinitrogen with -~., ... ----·~

early transition metals,

•

(b) preparation then reduction of model compounds,

(c)

such as Ar-

N;,

using intermediate transition metal

complexes of

thf;l

molecules.

relatively stable transition metal

, but in this case reduction of

not

Figure 1 , reproduced from Murray and Smith and updated, shows

. the transition which have been investigated for the three

types reaction above • reactions will now be

in more detail.

(a) most successful reactions in reproducing biological

nitrogen f!Jcation under mild conditions have involved

the early transition metals a. .... -. .... ~~''"' as reduction •

In

, the final '~"0_'"11_{"~""~"~ nitro9en product to be a metal}

nitride which is readily hydrolysed to ammonia. This reaction

biological systems 17• of the

•

6

are more similar to those involving dinitrogen interactions with

metal surfaces.

The most thoroughly investigated involves

( -cp)

2 TiC12

18

' 1 probably as this complex gives the

relative ytelds of nitrogen. schools of thought

as to the intermediate complexes involved in this titanium

Much of this work

Olivl:l 18•

recently reviewed by Henrtoi-Oliv~ and

The authors above 18 consider that the reaction involves a

dimeric hybride (III) - (II) , but the

bonding of the di.nitrogen molecule, proposed to co-ordinated

to titanium (II) , could not determined from the esr s

they obtained •

Van Tamelen disagree suggest that· no hydride

intermediate is involved. that in the ( 7( -cp)

2 TiC12

system, the initial reaction involves co ... o:rdination dinitrogen

to { Ti( 1r -cp)

2

l ,

with the formation of the intermediate

[ Ti(N

2) ( -cp)2

J

2 • Van et al.

20

that dimeric

such as by

Henrioi-Oliv~

Olive 18 are

only formed in the d:Lnitrogen, but these dimers must

dissociate back into titanocene before ~;:my reaction with dinitrogen

occurs.

Franklin and

Byrd~

1 have interpreted potentiometric

studies of the T1Cl

d:lnitrogen: titanium complexes possible, depending on the solvent used. Possibly this explains some of the problems in interpretating the titanium cyclopentadianyl system above.

Yamamoto et al. 22 have isolated a series of nitrogen containing complexes from reducing (TiC1

3 (THF)3

J

with

magnesium at room temperature in the presence of dinitroqen. The initial black product analy:;;ed as {TiNMg₂c1

2 (THF)) n. Five

moles of reductant are required (2. 5 gm. atoms I\l.fg/mole T1) and the product gives no dinitrogen on pyrolysis at 200°C. Part of the magnesium chloride can be exchanged for aromatic amines such as pyridine.. The authors consider the complex to be either a

dinitrogen bridged system with a low NN bond order, or a nitride with a low TiN bond order ..

Further work on the above titanium nitrogen complexes may positively identify the intermediates involved in the reduction of dinitrogen with the early transition metal complexes •

(b) Parshall23 and others 24 have investigated the reduction of molecules, analogues

to

dinitrogen, such

as

Ar-N;. These mole-cules are co-ordinated to transition metal ions, than the triple bond

in the ligand is reduced.

From information at present available the requirements to

1. The metal th<Ute with the

to in

low

oxidation states , es pee! ally d8 electron

aonfif'Ut'atio~l

•

with the complexes should not be strong 1( •aoofa!ptor ligands*. The other ligands present in the aomplexe• ate predominantly aminea and phospbines together with

hydtide,

or

halide~~

S .. The :~~ource of dinittogen either dinitrogen (the metal

The

most

oommon nitrogen

oontllintng

molecules used in reactions to

• The unus 'Ltal

reaction in Which ammonia to dinitrogen in the presence

ruthenium (lli) (IV) and a reducing aoe:m:

*

A number. of impure diruttogen complexes oontaintnv 1( bonded ligands have been proposed

recently

but

formulatlon.s

such ar&ide$, also seem oonsi•tent with the evidence

by of the techniques listed below.

(1) lnftarettl sp$otra by identiftcation26 the

~

(NN)

iilit!JOI'Ption around

2000

om""'t. If

the

15N15N

illotope

used a !n energy the ~ (NN) absorption

60w70 om*1 whloh is good evidence for the

~.~,""lfi!:;IJ.!>vw of dlnlt.rogea !I

Pteouation•

have to be taken

~tu>slenc:'e of d1n:Ltrogen, e ~ (NH

3) 10

CN

2

)J ,

2 000 om ·l may du4!1 to

the evolved , by

in!lrate~d $peotral and

t1A1~At1 for most

A brief survey wUl

cUlJ::tea•·anc~e of th•

have been repOrted and •. .u~.,'il>

tbeit Pl'Ql)el'ties) are listed as

(together with

ll

Ptobably

the

most

·tntetesUnq

new

the

bridged

dinitroten

prepared

_. ' . by Ohatt•• . vroup80 ,31 , Item the

:published but the btldted complexes do have e~remely law hqueno!es (i-e down 1630 om•1 with Nbdl_{5) for} the

~

'ttN) infrared al::u~orption., in ~ (NN) absotption

energy

t

compared with

or

4

-1,3

0 f

J,•::a;:~.~.AQ

comPlexes

may

both prepared

M(N₂)it

3(PMe2Ph)3

34 _and

(where M • ~au,Ofll). frequency the ~ (NN) (!absorption in

<

ltu but the stab:Utty of

in the

dlnitrot~u:'t,

~

In the

oomplexes

38 , viz

13

the first complex, the use of 15N16N oonf1tml the existenoe of a dinitr~gen · oomplex. These two (X) carbonyl products in which

abwe

aU.lO

om'""

1

I

'

show the ird1u~noa of 1f bonding ligands

on the '"""'"''"" .. (i) dinitto~l). Vlillllj;loi.'IZII~ID whioh not contain carbon. the ll (NN) absorption

app~Ximataly

.

cnn~

1 in their inftllfad spectra.

ftl• oomplexea

OOtll)et (I) "" and

( lu(d1ars)₂ (N₃)

1

•

However

1 the

(d1m)₂(N

2)olJ can he prepared (rom thil

az~A:t.e

,

a

reacucJn

involving

NO+.

et al,

44

"""'''"u,,.(N2)

2)

(1Ph4)2 t

rennn~Etn by

probably

·~l'<'IIIIU"""' OXJ.aa1:1on

states,

probablY

detected'U)

(W), (ita _oase the •etra.phenylbcrate

talth

ll$o~

et a1.

41

have

~nftrmed

the

poeJd.bUity

<»d.dat1on

of

llmmirte

•

'-'bey

1howed

that

both

[oa(»m

3) 2

>J

a+

and [Ru2

CN:a:

1

>

10tN

1

)]

4

+

wtU

unaerg()

ayoltc,

one electron.,

oxidation then r.duotion raaotione 1ft

euaueou1

(25°C)

• H2S04 I01utton. fb.e

te.te

donflt&ntl for the deoontPOsitio:n of these ox.td!.sed complexe1 Z x

1(t'•a

fU\!I0•1 and 1 x

ut•l

sec""l

re•pecUvelv47 •

monomer

[Ru(NH

₃

>1

a+

oould not

oxtdl$ed

W•

compound g1V'Il!tl

an tmmedlat€!1

evolution

dtru.troge:n 4

7 •

bean

develo,.a

40• A mtxture of the two ruthenium dinttrogen

001tlli1lfl:H! ions [

1\u(~a>&

(N

all

l+

~d

(

) to(N2)]

4

*'

I

l)fe!oar•:td by the decomposition [ ku(NH

3)8(:N3)] z+. that acid rea,Ctl

wt'b

the u:t<le ttarting mateHal

to firat gf.'Ve

a nltrene

intemedtate, wbtah

the dlnlttot«!ln product&.

tufther

react•

form

(d)

J!nu&oa&.

Pf.Q~Jf!A•e, ft~. ~amto

1Jiaiaf

•l•

4

1

others

49

,so

have

addittoaal

N

Ill

N

'

End on co.-ordination (A)

..

_.

_.

_.

_.

\;

Ru

I

NH3

Edge on co-ordination (B)

F&sut! 3

Posa&bl!

Mml!• gf P2~atd&lgt!op of l)tpitrosusm

tQ the [ Ru (Na₃)

ion [ Ru

2(NH3) 10(N2)

J

-4+.. is on on the first reaction producing { Ru(NH

3) 5 (N2

)j

2

₊

as prodll,ct,

but on the second reaction cannot compared because of

variations in ionic strength present.

'l'he enthalpy difference between the two possible modes of

co-ordination of molecular nitrogen to the ruthenium ( II )

pentaammine grouping (Fig .3) estimated51 to be

approxim-ately 92kJ. mole -1 by considering the activation energy for the

reaction 1 15N Ru - 15 N. intermediate

in this reaction , but the

activation energy means that this intermediate is only

slightly more stable, (29! 17 kJ. mole""1), than the nonbonded

system composed free dinitrogen and {Ru(NH

3)5

J

2

_+.

(U) .... Gray al. 52 have assigned the intense

absorption at 200 ... 270 nm in the spectra of ruthenium and osmium

dinitrogen complexes to a metal to ligand transfer

transition. For the dime:r, £Ru

2(NH3) 10 (N2)

J

4_{+, the transition.}

*

2+

eu ~ e

9 ( N2) while the monomers ( [ l\/I(NJ;13) 5 (N

*

=

Ru,Os) the transition is of a similar type (b

2

or

e( N2).

Gray52 proposed that the total bonding electrons transferred into the

*

NN

dis:tanoe Comments (pm.)

CoH(N

2)(PPb3) 3

[Ruz(NH3) 10(Nz)

j

(BF 4) 4

111.4(11)

191.816)

{ Ru(N₃HN₂)(en)

1

j

•r

6

[ oa(NH₃) ₅

CN

₂)

1

1

(I)

'*

(1)

pteaent

work

•

energy end consequently the energy of the Ruthenium-:~~( "'T' N 2) transition 1s lower.

Ohatt et • 53 hal competed the ftequenotes of the

~

(CO)

8nd

J

(NN) absorption• 1n a number of isoeleotronio carbonyl and dilliti'OIJ'In OOII!PlexeJ •

It

was shown

that

the ratio of

;~~~~

t ls identical and equal to 1. 088 for all isoeleetronic pairs

considered*, including the free ;a1eu•• This li interpretated53 in termi of the similarity of the type of bonding of these two molecules

metal

ions.

(e) ~tructuref. of :P&n&trogen . Oomslexe" • At the structures

of &be dlnitrooen eompleltes have been determined by x-ray methods52'

ti-4•S 7(Table 3).

tn

the four struatures theN bond

!enwth

ranges from 112.4 pm52

for (au

_{2 (NH3) 10 (N2)}

J

OaF

_{4> 4} to 110.6 pm55 for _(Ru(N3)(N2) (en)

2] PF6 (Table 3), compared with the bond length of dinlttogen in the gateous state of 109.8 pm58 • The metal dinittogen bond lengths ranve from 180"

1

pm54 for

(N2) (PPh3}3 to 192.8 pm for

£

_{Ru2 (NH3) lO (N2)] (BF 4) 4 •}

tn

each M "" N N ~oup ta linear to within a few

..

The data on the two disordered str\lcturea56 ,57' 1s

but

is tn overall agreement with the

reaults of the ordered structures,

The sign1f1ctmt observations from these dinitrogen structures

are

abort metal to

dinitrQQ"en

bonds, the

linear metal...,.dinltroven

* ~ (XY) 1 , is the energy of the observed (XY) absorption for

m-oup and the little changed NN bond length in dinitrogen. Simiiat Qb~t~ervationa apply to carbon monoxide complexes • Probably the mo•t stvnificant ob~t~etvaUon 18 that the mea1ured

meta1•din1ttoven bonds length• we almo1t ident1oi!U. to reported

11

The aim of the prel)ent work wars to add

te

our undet~JtancUng

of the chemistry of c:U.nltrogen a ligand.

P!ft!

(a)

Wh$n

this present

work was started it

wa1. thought that dinltrogen 1n the QomplexJion ( Ru (NH

3) 5 (N2)

1

a+

could teduoed to yield one mole of ammonia60

,Gl,

while the other

nttrogen atom was unaoaounted for. The diW.trogen in the few other know!\ complexes could not be reducea11.. The complex OoH

(N1(P~)

3

that th1s compound

together with the ruthenium compound suggested a model route2 ' 11 for biological

dinttroten

fixation.

it

was hoped to study why the

then in

2+ of impurities in samples of [Ru(NH

3) · prepared utdno bydrazine hydrate • the original reperted60 methcn:i • The

impurities contain b:ydrc:uctne, probably as the complex ion

N₂H₄H₂

o

<o

0

_{c .. ,}

10 mins.

(Ru(NH

3)

Cool in Air.

Itt"

Mixture (Ru(NH

3)5(N2)J Cl2

Hydrazine reduced

"'---llHJ.---

and (Ru(NH3)5(N2H4)J Cl2

·to Ammonia

FIGURE 4 Reactions of tRu(NHa )

6 Cl

l

012 7"-'ith H:ydrazine Hydrate under various conditions

(This work and refs. 62-65)

Mixture (Ru(NH

3)5(GO)j Cl2

and [Ru(NH

3) 5 (N2

)J

Cl2

by a lingle ..,..,,.,..,,.. 1> ThiS 111'1'1'11.1t'1'1:'UI'~ iS ~ ... ~.,...; $:tld

the

oa ...

N₂ bond length l84;o2 , the N N bond length is

:U2 pm and the average

os ....

_(NH3) bond lfllngth is 214 pm.

OaNN bond unole 17tl'' the environment the osmtum is

•

(dJ The solid

solu"ttons

[Ru(NH

3) 5(N2)] 012 in

(~u(NH3)50l] Olz ~nd in

LRu

)

s(CO)

J

have been inveltigated.

These

mixture•

form solid solution•

in whioh the dtnitroven

group

probably no

longet aulllorcLenu:t with

the

:::~~mmn1ru :::~~ ligands a1 oac1urs

pure [Ru(NH₃) ₈(N₂

)J

•

of this work it decided to investigate complexes of penta•valent rhenium containing the species Re ...

o.

The short rhenium-oxygen bond confers a strong tetragonal dist,or.tion to octahedral tbenium (V) complexes and this gives tise to spin pairing • The complex s'

2ReOC15 has been reported as patamagnettc:-? 0

20

complex is in fact spin paired with a small positive molar

susceptibility due to temperature independent paramagnetism.

The reason for the high magnetism reported earlier is due to the

first

no~)Gd. that ..

u•••v would enable

to understand

the abilitY

nitrogenase

this knowt.d;e may

the of cunttt<>Oelrh

molecular dimtrooen.. Eventually

Qther eoonomlo !ndustrtal method$ for

This imminent when Allen and Sal1toff

... Ql ... ..,Ui [Ru(NH

3) 5(N2)] ,2·+ could

to yi$ld mole of Nthl!l.inium.

time, CoH(N

2

)(P~) ₃

tr(Na)CUP~) _{2 ,} csec,omiDOJ•ed. wtth evolution dinittogen on reduot1on36 ..

the

the The

0 .. 0 ({.} c: ro ;.... £,-; ~

0 ..

4000

FIGURE 5

.

'

•• < ~

Infrared

;lio~ .. ·~·--" ...

2000

..

_.

i ' · ... ,

..

.

'

.

' ;

..

~~ ' _.

.

_' ''

.

_{' .} '

.

_{' I}

.

1200

1600 l

Wavenumber (em- )

(NH3) 5 ) ] ZnC1₄ i) . . .

(i}, product is

t

800

.H2

oxidation

Pudfioatton

Reaction• cf [ Ru(NH₃)

s

(N₂₎

J

Cla were initially our!ed out on products at room temperature by treating

(Ru(NH

3) 501

1

01

3

with ·bydtalid.fte hydratE'+

When this

is evolved but a "'u''lii!UJLt.;U1..Jull! I,;I,It:;l,!iUI.i.t.dl~11!:!

of

with [ rtu(NH3)

61

(HgCl₃) $ , m-eoared t

14

by the addition of mercuric

to (itu(NH

3) 6] • However, I!SP&ottum

2015 om ""'1• The

an

attempt

to

~ ... ..,..,li of

anions

a-Table 4

Property

)Leff•

Infrared ~ (NN)

Ss(NH)

fr(NH)

+

Analysis

Cl; H: N/Ratio

Properties of the Two Products formed from

the Mercuric Chloride Oxidation of

[Ru(NH₃)

5 (N2)) 012 (Hydrazine Prep.)

Product 1

0.6 B.M.

2115 cm-1

1302;1285 cm-1

775 cm-1

4

.o:

16.5:7

.o

Product 2

2.3 B.M.

1340cm-1

800 cm-1

4.8:20.0:6.0

Conductivity/Cone* 2.22 x 10•3

(in H₂o) Moles/1

1.93 X 10-3

Moles/1

+

*

Molar* Cond. 240

No effect

440

Reduced to (Ru(NH

3)6 ] Cl2

The analytical figures given in the experimental section at the end of this chapter.

Based on the molecular formulation [Ru(NH₃)

5(N2Jznc14 for

Most of

the

remainin~

ruthenium

could be recovered

from

the filtrate;

from

wbiob the

ZnCl~""

aalt the dtnitto;en product h$d been removed, by addition of

methanol

(product 2). The properties of

the

dinitrogen prOduct and the methanol precipitated product outlined in Table 4

*

The latter product, product ~ ~ bas

ProPerties

wh1<:.1h are

consistent wtth a

oompound

of

oompc:ur;ltion

l

i\u(N.H₃)

6) Ol.Zn014 ~ A product with identioal K•taY powder photo, infrared t~peotrum

and

analysis to

proouot

a ,

is obtained when the

cation

[ rtu(NH

3) 6 ] $+ !s precipitated from an

aqueou•

solution by use

of I!l'lino chloride and methanol.

Produot

1,

the dinitrogen complex

precipitated as the

ZnOl~­

salt, was mOta difficult to explain~ The

x ...

ray pQ'W'der photo of this product is identlaal to the POWder photo of (Ru(NH₃) ₆

J

_Zn014, hence the low ma~netic moment of this compound is consi~Jtent with

a.

monomeric ruthenium

<tl)

complex~ However~ some ptQpetties of this new complex (Produot 1)

in the air at

room

temperature and the pale

yellow

so11d darkens to a blf.tok powder after •

few

days if The product obtained by the

KUt1'4H,.)

B

}

J ,

(Ru(NH₃)

5 (N2)

c1

2 • and possibly

1\U\,N,H'!!it)

J

a

of

(Ru(14NH3)(15N1SN)

J

2+ •' ooraftnned this.

tesult

80 • They found no

rGcovered from the d.ec:::onl:PC,S1t1on

,·a number

entiohment of the

(Ru(14 )

5

t

15w15:N) ] (IF 4)3 with hot o.i

:meentlratE~a

sulphutio or alkali borohydrtde ,,; also found £~Jolut1ons of

IUttilOaJedlY pure _(Ru(NH3)

5

(N2

J

,

using

hydrcu:ine

hydrate, a positive than 6%

hydrazine was found to be present• Allen•s6

0

original aompound a high hydrogen

analysis

Whiob his preparations

26

tdx moles of ammonia" The additional of anunonia comes

from the hydrazine imput!ty and the co-ordinated c:Unitrogen.

in th1$ chapter (see beloW') it was found th-.~ approximately S. 7 moles of ammonia obtained from the decomposition, of th~ hydtazine pteperatton of

~ ' '

( Ru(NH

3) 5 (N2)] 012 , by strong alkaU in the presence of

Devardi!l 's

alloy.

ruthenium complexes such

l

Ru(NH₃) f~NaJ

J

'

(a•ide preparation), ( Ru(N:a₃) ₅

ot

1

01₂ and

(Ru(NH

3)

al

01

2

give

only

the molei:i ammonia predicted

supports the that their oom~X'sit1on. This

otdinated hydtazine 1$ the SOUirCe the additional •

l;),..u, .. o this published et al. confirmed

tha' co-ordinated d.tnitrogen.in {Ru(NH₃)

s

(N

2)] 012 oanno1:

with alkaline borohydride • However, these workers on to say that even ( Ru( _{) 6}

J

moles of ammonia, when hydride, in

Attempts

potential$ of

without

conditions

gives ~eater than the predicted

is

with alkaline

bore•

by them.

reduotion

{ Ru(NH ) (N

J

J

z+,

but

3 5 2

that oo..,.otdinated dinitrogen "stable" oornpleXE~s m:UlllC:)t

(

]

Lever

28

relatively

(a) ,Rf!&qtii!l

w1tb

merow1C' oblgride .-. Tht• work

been described :ln the .,...,,v .. ;ru;.,. secltlc~n

... Both

oontam1lna1:•ea ( Ru(NM

_{3) 5}

(Nz)

1

₀₁₂

I"A!ll>l"'''''

with

.,,. ... .,..,,.. OOCUt$ wrul!t'tiiU;il!!

73 ,7~

and hydtaa:ine

ln solution

evolution with

formation of a yellOW'

solution.

purple

from

both

"'"'""'~,.,,.,1;:>

to the

V

(NN) yellow solution

ruthenium (UI) ~Au,u~·~~"""" while the u.: . . n •. U.H, from the purple solution

did

net contain

oo-"o~a.J.natEia

ammonia.

the formatton

(o) Reaction with ( Go(N

eimU.arly

to HgGlz

.-.olution. The

hydtazine impurity

[l\u(N'H

₈

)

5

(Nia

4)

1

l

Ru(NH3) 6

1

i+,

//

4 _{are both}

...

~,

... .,...,, ... to

rutheruum (ttl) ; but [ Ru(NH₃)

5 (N2)

1

3

+

(d)• d ruthenium

tn

[l\u(NH₃) ₅ (N₂

)J

c1

₂

ami

(Ru(NH_{3) 6}

1

to

ruthenium (U.t) with

dltfowuted tn in 5" The

hexaammtne

[Ru(NH

3)6

J

012 tepgrted

to react

dt~erent1y1

3

,'1<4

linoe

ord.btated ammoma 1$ al•o lost, and the

produat ( Ru(NH3) S (HzO)

ClaJ

01.

ED

• The two rutbentum (t!) ClOrrtPle:xes

[au( ) ₅ (N₂)] _o12, L4""'''4".l;!..l!!l) ₆

J

_o12

13

, '

4 wuh

nitrous

give

nttto•Yl

l

Ru(~p)

CNH

_{3) 5}

1 ·

(g) ... sodium

. 30

(autN:a3

J

6

J

cn

3

give

• The

~~P~ trtu(NHa) s(Nz)J r tAu(NH_{3) s} (N_2H4)

J

, .

deocmn:Jes••d

.under

ln

the

aDaJenc'e

.of

'l"'hMr~tm

of ant.mpn!a1 wmare1m the complex[Ru(NH₃) ₆

Jo1

₂

rea,ots in hot

wflltl!r-whUe

thllil

~IIU!J.f!~ny CO!lrJPI.i'X l& ""'""""''""'""•~,. ....

with mUd oxidising agerntl,

4itUtf00'4\Jl'l OOll!i:PlEtlC

have

13,

Mbenium as

metal,

ruthenium (UI)

ammtnes I!

(Ru(NH$)

S

_(N2)

J

₀₁₂

oondittonl ,

hut

and (

co(NHa)

6

1 ,

ru-c:neru\Jtm

(Ill)

..

l

au(NH

3) 6

J

oxid1aecs'3 •

14

[

au(NH

3) 6 whUe (Ru(NH3) 5 (N2)

J

:t+

o1v~:ls

pent~uamm!ne suoh ( ltu( )

5 Cl

1 ..

v"""''t.Uo.,i>Q to similar pteduota as obtaine<I the <lm&vogen oompl~.

1

32

(Found N, 34.6~, ₀₁₂

a

_15N71tu reqUires N, 34.2"). other $alts

aueh

the

ZnOl~'""

aalt we prepared .by

dissolving

tht• impute complex in Wi\ter, then $dd1Uon of the apptopt1ate anton precipitates

requt.t.d

lalt.

These salts were QOt analysed as

they

were

known

at

tht•

to

be impure.. Put1f1oation

_{[1\uCN ) (N2}] 01}

₂

(bydta~Sine preparation) with HtC1₂ • ~e product obtained Rnt'i'Va

(0 .1 g;m) was treated with saturat~ aqueoua metrourio oblotlde solution

(1.1

mls). After the prea1p1tat.a mercury oompounds had

flltetf~Jd off, ammonium chloride and

21tno

chloride w•re added to preciplta'e the pure

c:Unitrogen

complex

[Ru(NH

3

)s_lNa~no1

4

•

Thill~ repreotp1tated ftom water _{NH 4 01} and.

Ltli."-"'*"'. (Yield 0.02 gms). (Pound

01,

*4~- (NUa

only),

_{16.1%# Cl4Hu;NJ}

N' (total) ,

-·--... Cl, 33

.6"1

,

3.6~;

N

ft:ota1),

.~~~

N(NH* only)

ts ..

s~l.

~l!PM•UPD

Qt

hexapmm&ne . rutl1en1gm.

'BI!

~o~lortde,,

teuaon4Qtgatno

.. , . ' '

(Dl . ....

'

M~

''t

Methanol was

"'""'Y.'""'

[Ru(NH3) 3

(N

₂₎

J

-~

.. --..

atvan aomTe.

, 4.4"J N, 18.9~; Cl~a

11

N

6

RuZn .. ,... ... ~ .... N,

18.8"h

MeJhP$1

{e)·

The -w•••.r ...

U'll~n.ea _{with NH4Cl, and ZnC12• The product was preotp!tated}

Preearljlttm.

gg

:Pep,tatmt.llinedintttgflcan

Qrth~a&urn.JW

t.eir•~~l~~o~ino ~}q

•..

~

_Ru{NH3

li,

~~

3

)]

.zncl

₄

~

34

First

row

complexes

11 "

ln contrast,

ruthetd

um and a nurnbet

othet

•econd

and

third

tow

tranettton metal comp"'xf!J.uJ react to

etve

e.

number

produots which

Am•r>llilSt the ""'""L·""·""'"" .. J.O.I>UU!.4.,.. • • mDOI'tll:tt!! and a yellow

aomrx>und whlch wtth

red aon!lPO'una has mote recently been

of 4umeJ

[fb.t01

5

(H~O )}

3

~

or

'

the

IW'I!!Inall'attt\'1'1

'l'tttl"l"\ttAn

aom:Ptex

£

Ru

) s (Ns)

1

by

Allen

the

that

compound has

~BubsE~tquently

DI'C4!lUO'l8 af8 OD'9;,BlJl~Ml QCHltlil!UilU

""'""'-'"'""'"'Ill}~ )

J

I ( AWU'll&1f6# ~

]

a .bisdinitrogen

36

. 2+

complex ion ( Ru(NH_{3) 4 (N2)2}

J

and the new complex

[ Os(NH

3)5 (CO)

J

c12 has been obtained. The latter compound

was also prepared pure by a different route. Evidence for a species

Fe(dtc)₂ (CO)n has also been obtained.

Results and Discussion (a) Compounds •

The work will now be discussed in tE;1rms of the compounds

prepared.

( Ru(NH

3)5 (CO)

j

Cl2•

The tervalent complex (Ru(NH

3)5cl] 012 gives a deep red

solution when it is dissolved in hot (80°C) hydrazine hydrate, and a

vigorous gas evolution occurs • The ruthenium containing complexes

can be precipitated with either alcohol or ammonium chloride, after

cooling. The product may be either a deep red or yellow, the colour

depends on the time taken to cool the solution in contact with air.

The red product is obtained after rapid cooling, while the yellow

product is obtained if precipitation is delayed until the solution has

stood for about one hour. The infrared spectra of both these products

are identical and the same as the infrared spectrum of mixtures of

[Ru(NH₃)₅ (N₂)] Cl₂

I

[Ru(NH₃)₅(N₂H₄

)j

c1

2 (see Chapter 2)

except for the addition of a sharp absorption at 193 0 em -l • The

component, giving rise to the 1930 cm- 1 absorption, could not be

separated from the

l

Ru(NH

3)5(N2)

J

z+

known to be present ..

A similar reaction occurs when divalent ruthenium (as

LRu(NH

3)6

J

Cl2 is heated in hydrazine hydrate, but relatively more

(j)

u

c:

ro

+-'

+'

...

8

~

o .

4000

FIGURE 6

2000

Infrared Spectrum

1200 800

Wavenumber (em -1)

[Ru(NH

Table 6 Comparison of the Properties of (Rhli(NH

3) 5) Br2

Properties from Propertieu Reported

Present 'Work ,by Wilkinson

Infrared S;eeotrum (om -l)

~(NH) 3285,3190 (sh) 3276, 3186

~(Rh•H) 2013 2015

Os(NH) 1610 1609

.5a(NH) 1275 1278

Pr(NH3) 813 820

~(Rh-NH

₃

) 480,448 483,452

8(NH

₃

·Rh~NH

₃

) and 265,157 (broad),

Low

freq. Lattice Modes 87

I.R.

Other, probably S (Rh-H) 1185, 1170 (sh) 1171

Ultraviolet, v;t,sible Spectrum (nm)

205

233 (sh)

305 (w ,sh) 3 07 (reflectance)

350 (w ,sh)

Reactions Dilute acid - New Product, as CC, [RhH (NH₃) ₄

Halide ion

in neutral

solution.

~(Rh-H) at (H₂

o)]

S0

4

2138cm-1•

Mbced rhodi urn (III)

amine halide

products together

with .rhnrHum m@btL

formed,~ (Rh-H)

at 2146cm-l

Rhodium metal

and mixed

ammine halide

of the

by repeated r<eact!ons, on one rutheniun1 sample, . u.stn9 fresh

•ample•

hYdrill~ine hydrate • · MalY~is of a •ample obtained from

{Ru,Nl3;~)

el

c1

₂ showed that it contained 3 ·1" carbon, it appeared that the ~>roduct Wll$. <;=~mpQsed prtnoiPallY of [ lu(Nii3) 5

(NalJ

Cla

and

_{(Ru(NH3) S (CO)}

J..c1

_{2 • The . .,rocluot oan} be obtained in the .

... of

organic

solve~ts

and

carbon

oontaininr;

compoundS~ t pt ·

for the traces of carbon dioxide dissolv$d in hYdtazine hydtate.

. .

P~te [Ru(NH₃) ₅ (CO)]

c1

_{2 was then found to be readily}

ob~ained if additional carbon dioxide was dissolved in the bydrazine

. . . , . . ' ' . . . '

hydrate, u•ed in the reaction. Vndet.these conditions no deep solution is formed~ . This carbonyl product, the infraril:ld spEH,trum of . which ts shown tn Figure 6, has been prepared Ptt!Wiously by the more

lab~ous

6

_7,GS

_{method of reaoting carbon monoxide with}

l

Ru(NH3) ₅ (H₂o)

J

2+ ... The properties desotibed

for

this oomplei7 ,sa,

851_{ate identical to those of the carbonyl ptepared duting thia present}

,

l}~hH(NHal

s}

_,Bt3 Rhodium trichloride and _(R11(NH3) ] c1₂

teact With :~lno in ammonia to gtve the hydrtdo-oomplex ion

l

Rh(NH3)

sH ]

•

The pure CQm:Plti!'¢ can be Obtained by precipitation

of this bromide salt have been measured (Table 6). Wilkinaon et l;ll. 66 have since reported the isolaUon of this compound and their re~Sults are similar

0 0

Vi

:z: """

.::>:::

,__

""'"

0 '

4000

I

~

0 0 0

~ 0 0 0 Cl> N

""'

• 2000

. . ( -1)

Vlavenumber em

FIGURE 7 Spectrum of [Ir(NH

3) 4 (CO) Cl]

ert shows formed diss

' ~

800 400

The complex RhC1

3 .nHzO reacts with hydrazine hydrate ot

hYdtazinium carbonate 9iVe a product with no absorptions near 2000 om""'lin its infrared

spectrum~~

The ptoduots appeared complex and

the infrared.

speotta sugc:;ested that o~ordtnated hydrazine was present-. Further inve&~Jtigation did not seem warranted,

l,

Ir(NHI) ₄ (CO), C1 ] 01~ ~ An ilu;oluble form

of trcla

and the complex ir(NH

3) 3 Cia:, react with hydrazine hydrate with zinc dust in oonoenttated ammonia give similar products all of whioh have an infrated absorption 2078 om ...

1..

The product obttd.ned from the zino in ammonia reaotlon was the only one th<at oould be purified

further and was the only one to be

more

fully investigated \o

After reaotion with z1no tn ammonia, irtdium product

in water and quickly removing an insoluble of mainly zinc

hydto~ide t The ptod.uot is obtained by freeze drying the filtrate~

lt

is necessary to wotk rapidly as the carbonyl decomposes significantly within five m!nutes tn watet, but it is

The product, wh1oh never obtained eompletely pure because of 1ti instability in and insolubility in othet solvents is postu;.. lated as a carbon monoxide derivative on following evldenoea (l) !hAlt complex an intense infrared absorption at 2078 om"" 1 ,

39

I.!Oid produced a gas of mass 28 together with a

•li'•,.,a

of hydroqen. The iridium product remaining in solution is ~=­

{ ir(NH_{3) 4}

c1

2

l

Cl whiob was identified by analysis and X•rav powder photography,.

(3) Aoidio oerto "'"'""""9".""'"'~ and thermal

decomposition

both gtve a

oat~ of maas 2$ whioh was identified a mixture of dinittooen

oarbon monoxide. Some

d!nittogen

aan be obtained from

[ tr(w

_{3) 801] 012 ,}

by similar

decompositions. Analysts

of a

sample of the complex shQWed carbon to be present, and the

amount (2%) $U9frJests appronimately 60% purity, based on the formulation [ lr(NH

3) 4 (OO)Cl] 012•

(4) The compound is

isomorphous with [Ru(NH

_{3) 501}

J

o1

_{2• This}

suggestat a di positive cation with two chloride anions" (Faint :Unes corresponding to mt

4

Cl

present).

fS) The compound is diamagnetic.

'.l:m1o

6

=

-113 .. Diamagnetic corrections for (lr(NH₃)

4 (CO).Ol ] 012 are

•.138 x Uf"'6 oga,. {tnalus!on of eontrJ.hutione the probable impurities,

evic:tanoe il oonsl~S,ent with the propcuual that the new proc:tuct (Jr(NH₃) ₄ (00)01] Cl₂ h~,t$ bf:)EU\ fotmedtt

]

1919

l&(c)

a

ceo)

2051

40

at 2120 om·1 , (Figure 7)., Dilute acid catalyses this reaetion whereas strong ammonia solution or reverses the reaction.

a sample of product with both the 2120 om ... 1 and 2078 om'""1

absorptions in the infrared spectrum is dissolved in

o.sso

ammonia, then

fre•~e

dried, the resulting product

M.a

only the 2018 om-1

o.sso

(i) The addition of ammonia reverses the !n~tial reaction, this

would

requite that the initial reaction involves replacement of

' '

some ot all the co-ordinated ammine groups with solvent water. (id The addition of ammonia ' the component of the mixture having a 2078 om·1 absorption in the infrared specttumJ the other component; with the 2120 om ... l absorption, still decomposes • but with no repleniehment through reaction of the "2078 om-

1

component~~

A having only the 2120 om""l absorption in its infrared' spectrum could not isolated, hence the two explanations (1, il) Dl"ti'WII'A could not be """""' ... """' to distinguish whtoh aorreat"

No evidenae obtained completely confirms the

dinitrogen but

on

..,o,~"'"" of·oomparisons between

known d1nttrogen it that iridium

e.rnrn1ne, dinttrogen

COltnUIO\U'lds unstable isolate"

Monooarbonyl such as ruthenium (Ii)

supporting evidence to the proposal that the compound prepared during this work is an iridium (II!) carbonyl. Presumably the iridium must first be reduced f probably to Ir(l), before any stable dinitrogen

complexes are likely to be isolated"

The compound It(NH

3) 5, proposed by Watt88 to be the product of the reaction of [Ir(NH

3) 5

c1]

012 with sodium in liquid ammonia, was prepared to see if it was a dinitrogen complex but the infrared

spectrum of this product showed no absorptions near 2000 cm""' 11

ruling out a mononuclear dinitrogen complex. No investigations to check for a dimer were made •

The complex {Ru(NH

3) 5

c1]

012 reacts with cold ( < 0°0) hydrazine hydrate to form a brown solution. No further visible change occurs in this solution after standing at < 0°0

for one to two hours •

The ruthenium containing species in this solution can be

isolated as a brown solid by precipitation with sodium bromide. The infrared spectrum of the solid, after precipitation shows absorptions characteristic of hydrazine together with a absorption at 2105 om"'" 1 , attributable to the ~ (NN) stretch in monodinitrogen, ruthenium (It)

If the [Ru(NH3)

sCl]

012

I

hydrazine hydrate solution is left

at "0°C for longer than one hour before the brown ruthenium containing

l1.4YENUHBLR

2200 2100 2000

After one hour

(no change a ftar OM week)

After one year

FIGURE 8

two ~ (NN)

44

identical infrared speotrum tba't obtained ptevtously exoept the· 2230 clm*1 and 2130 om""1 both relatively more :c.n'tl"lul

mre~'!t.er

proportion

new

pr()duot

( Ru(NH3) 4 012

J

of

~is;,.( Ru( )

4CN2)2

J

Bt2,

of

rreeu11rulr>l'Y this reaonc>n

co ... ·ora.ln~lea hYdlral!!t1ne in this

obtained by

and

,

All

the1e PNPM''El'C11()Ill QOllll.lll\lrag

muoh

the

43

instability of the complex in solution" Hence the existence of this

bisdinitrogen cornplex can only be proposed on the basis of its

infrared spectrum, preparative method and comparison with

ci,!_ ,... (Ru(en)

2 (N2) 2} Ph4B)2

44_{.. Possibly the most interesting}

thing about the two ruthenium bisdinitr:ogen complexes

cis -(Ru(NH

3)4 (N2)2

J

Br2 and cis .. [ Ru{en)2(N2)2]CBPh4)2 44 is that they differ significantly in their reported stabilities in the solid

state.. Co-ordinated ammonia or ethylenediamine could be expected

to behave as very similar ligands , in complexes but the stability of

dinitrogen as a ligand has previously been noted93 to be very

sensitive to minor changes in the metal complex to which it is .bonded,

Impurities can also have larg-e effeots on the stability of dinitrogen

complexes and on the frequency of the

\>

(NN) infrared absorption

(re£ .. 26 and ChapterS}.. An additional reason for the observed

stability of the bisdinitrogen complex cis -(Ru(NH

3)4(N2}2 JBr2

relative to .2!!,. -

L

Ru(en)

2 (N2)2

J

(BPh4)2 could be that hydrazine

impurities in samples of the former complex, continually decompose,

to produce more of the bisdinitrogen complex. :Outing this present

work an attempt was made to prepare

.9!!.. ....

(Ru(en)

2(N2)2 ] Br2

using the low temperature hydrazine hydrate reaction on

s!L.. ...

[ Ru(en)₂ Cl

2} Cl but without success • This observation suggests

additional factors may be involved other than the hydrazine

impurities •

( Os (NH_{3}5 (CO)}

J

Clz

Traces of the carbonyl

l

Os(NH

3)5 (CO) ] c12 can be prepared

;)(GO)

Sa(NH)

~(NH)

fr(Nma>

1898,1848 (sh) 1633

1316 ,13 OO(sh), 1298 808

~ (Os-CO), 8(0sCO) 604

Ultraviolet-visible ·spectrum No absorptions at energies below

21 Olllllm but has an absorption

above this energy (!.e. similar to the ruthenium complex).

Stabilit,X ....

'

.

Stable in hot concentrated hydrochloric acid

f

N

2H4 .H20

Boil with

co

₂

Os(III) or Os(IV) salt as cC

N2H4 .H2

o

Boil with

co

₂

1₂ oYJ.dation

in HCl

FIGURE 9 Cycle. for the Pl.\rification of

When a mbd:ure of hydtazine hydrate and hydrazinium carbonate is heated with either [ Os(NH

3) 5 C'l] 012 or (NH4) 2 (OsC10) ~ the product has a weak infrared absorption at 1887 em -l, corresponding to the frequency of the

J

(CO) ab(lotption in pure ( Os(NH

3) 5

(co)]

012,

(see below) together with a strong absorption at

_.

2008 om ... 1 correspond.-ing to thedtnitrogen oomple'c [os(NH

3) 5 (N2

)J

c12• The yield of

carbonyl could not be increased by any changes of conditions (e.g. by using Zn dust in ammonia.

The carbonyl is stable to concentrated hydtochlorio acid and iodine O!}ddation, hence it may be partially purified by the reaction cycle shown in Figure 9. Mechanical losses prevent this method being used for small scale preparations of the pure carbonylt but on a larger scale it would probably be feasible to separate the carbonyl after only one or two cycles •

However, a much better method to prepare the pute osmium carbonyl complex is to use a method analogous to that reported67 108 previously to prepare ( Ru{NH

3)5 (CO)

J

012• The complex

lOs

(NH

3) 5 01

J

012 was reduced with Zinc amalgam, then carbon monoxide was bubbled through for sixty hours .. The properties of this osmium carbonyl are shown in Table 6 and Figure l 0.

as well as the absorption at 1885 om- 1 due to the

~(CO)

absorption

of the carbonyl component •. Reactions carried out in air with relatively

low

partial pressures of carbon monoxide (about 40 mm) c;J.f:ve products which have little detectable carbonyl but have strong

v

(N:til

absorptions in their infrared spectra. Even at higher carbon monoXide ooncentrat ... ions, a little dinitrogen product was detected. This qualitative. evidence suggests that the reduced species; obtained from

lOs (NH

3) 5 Ol ] 012 ~ reacts with dinitrogen at a comparable rate to

its

reaction with carbon monoxide, especially as the latter gas is approximately 1.5 times as soluble in water (at 0°0 3.5 om3• per 100 mls compared with 2.33 cm3 per 100 mls for dinitrogen)12• Previously it

has

been ob~Served for ruthenium (II), that the rate

constants for addition of

co

97 ot N₂ 48 to tRu(NH₃) ₅ (H₂

o)

J

2

+'

are

similar.

In this case it appears 48 that the rate detetmining step is the

initial dissociation of the [M(NH

3) 5 (H

2

b}

J

2+ into a five co-ordinate

species which reacts rapidly with dinitrogen 1 carbon monoXide or

other substrates •

Fe(dtc)

2 (CO) n - The complex trisdiethyldithiocarbamate

iron (III) , Fe(dto) ₃ , reacts with hydrazine hydrate solution to give

a product with an infrared absorption at 2070 cm- 1 • Originally it was

hoped that this new complex would be a dinitrogen complex, which

~··· (]) () c fd 4-' +-' -rl E U) c fd I-. £:--; ~ o ,

.woo

FIGURE 11

/-~~/

,..,.., .. .;~·~­

..

~

tl t • • ., "' •' Ita.. 111o ~ " f l • 1

2000

r~ . .~·

:. / '!. .. ,.,... ! '•

..

~ ·"\ .... _ : .... : ~: \ :_./ \ ; ..

,

:· '•' 1200 (cm- 1)

Infrared Spectra of samples of Fe (dtc)

2 CO(n)

Product evaporation reaction mixture.

~~~~

·--- Product after reaction of above with HgC1

2 s c

,

-800

.,_

~.

proposed to exist in nitrogenase. The complex Fe(dto)₃ readily loses at least one dithiooarbamato ligand to give a variety of products, such as the halides Fe(dto)

2X (X-Cl, Br, 1,)90 and the nitrosyl Fe(dto)₂ (No)91 , while the carbonyl cis Fe(dtc)

2 (C:o)2 92

has been prepared although not by oarbon monoxide displacement of dithiocarbamate,.

Solutions of Fe(dtc)

3 or Fe(dtc)20l both react similarly in ethanol with hydtazine hydrate to give a product infrared absorption at 2010 cm- 1 • In both products Fe(dtc)

3 and hydrazine hydrate can be detected (irifra ted spectra) and use of t'e(dto)

2cl appeared to offer no advantage. The Fe (dtc)

3 can be removed by dissolving the product in water while the excess hydrazine hydrate is removed by oxidation with mercuric chloride solution. The yield of product, the infrared spectrum of which is shown in Figure ll,

is extremely low.. The two products in this figure are considered to contain an identical complex with an infrared absorption at

2010 cm- 1 .. The differences between the spectra are thought to be

due to variations in the impurities present. (Product(l) is known to have hydrazine hydrate present.

The evidence below suggests that the product with the 2070 cm-1 infrared absorption contains co-ordinated carbon monoxide rather

than the hoped for dinitrogen •

TABLE 9

Property

Infrared

)ceo)

Stability Heat

Colour

Comparison of Properties of cis ... f'e(dtc)

2 (Co)2 92

and Hydrazine PrepE!.red Fe(dto) ·'CO) .. Pro<\uct

New Product

207Scm""' 1

Both compounds have numerous other absorptions due to the dithiocarbamate ligands.

CO lost in cases after short periods of

warming.

gas composed of a mixture of carbon monoxide and dinttrogen. The infrared spectra of the sample decomposed above showed some hydrazine present, hence the evolved dinittogen. The carbon

monoxide suggests the presence of a carbonyl complex in the mixture.

(b) The compound cis•Fe(dto)₂ (Oo)₂ ts k.nown92 and this

compound has properties which are similar but not identical to those

of the product above. A comparison of the properties of these two compounds is shown in Table 9 •

The most probable composition for this new compound appears

t6

be one of the following two:

(i) trans Fe(dtc)

2 (00)2

absorption.

(ii) Fe(dtc)

2 (CO)

Fe(dtc)

2 (NO).

- one ~ (00) infrared

- analogous to the ni trosy 1

The lack of thermal stability of this new compound, together with the reported observation92 that cis - (Fe(dto)₂ (00)₂ can only be prepared pUre at temperature lesS than 0°0 1 makes

it

Unlikely

Hydrazine Hydrate

hydrazine containing products

J

and

1

Tbe

aotu~l .DI'Gidu~ot• 0D1:mz1ea

are summarited in

( Ru(NH_{3) 4 (N2)} g

J

l

4

J

sl

I

S (CC))]

not been

were • ( [RhH(bUi

3) 5

J

present worlt that

l

"'"""\"'U•it<'Jj/ ~

V\ll!IU&V.Ul

dinitroten

[ Os(J{rH

3

)

4 (N2) rea.u.Qtaon of Os (ll!)

and .. ~~\itV,Ul~ n,,.. ... H,.,.. {fl •l'!nlllnOl!l:l.f!llil

the 'I"W'o~:~tntl>,~•tt

(l) Reduotion

from. the

.;: .. ,:a%"""''".,."'~, probably the oat~nOJnv 1 omn.p,~;exe's from

pre:&Enlce Of using

49

(it) Co-ordination of the dissolved carb~n dioxide to suitable

metal ions ; then reduction of this group to give co-ordinated carbon monoxide.

The preparation of pure (Ru(NH₃) ₅ (00)] c1₂ using hydrazine hydrate/ carbon dioxide , but does not prove, that free carbon monoxide is not involved.. Ruthenium metal complexes; cause vigorous catalytic decomposition of hot hydrazine hydrate

solution to dinttrogen and dihydrogen

~

The proposed42 ,g 7 mechanism of carbon monoXide and dinitrogen addition to ruthenium (II) would

SU~iHJest that this dinitrogen $hould compete with any free carbon

monoxide for oo ... ordina.Uon to the ruthenium iont but no dinittogen product is obtained. Also the iron complex, Fe(dtc)₂ (CO) n

cannot be prepared using carbon monoxi.de gas and t'e(dto}₃ solution. ln this reaction; an 1.ron carbonyl complex (probably Fe(C0)₄, from infrared spectra 41), is formed and :l.t certainly is not the same product as obtained using hydra.zine hydrate. These observations make it unlikely that any free carbon monoxide is involved in the reactions.

The preparation of the dinitrogen complexes from the reaction

of ruthenium osmium complexes with reducing metals in ammonia is interesting as this reaction involves the o:ltidat1on of ammonia nitrogen in the of strong reducing agents, Chatt and

50

the reduction of RuCl3 with zinc in concentrated ammoni.a 1 but the

reaction with osmium, (as. Los(NH₃) ₅ 01

J

C1

2), under ·similar

conditions, to form the bisdinittogen complex cis [ ps (NH

3) 4 (N2)2] 012 does not seem to able to be exp~atined . by any hydride ·intermediate.

in neutral ~nd slightly acidic oondttions, with ~oth the +3 and +2 oxidation states

(Osmium (ttl) as [Os(Nii₃)₅Cl] 2

+

is qult.e stable, even to strong acid while osmium (II) as [ Os(:NH

3) 5 X) n+ (X probably t:l H20) is stable enough for it to take part in a relatively slow reaction w!th carbon monoxide or dinitrogen). It seems unreasonable to suppose that the LOs(NH3) 5

1

group will be less stable in concentrated ammonia, but it is still pos$ible undet these conditions to prepare a bisdinitrogen complex in a reaction of less than ten minutes~ It seems that the oo .... otttinated ammonia, nitrogen atoms must supply at least one of the nitrogen atoms in the resulting oo•ordinated dinitrogen groups.

The initial step of the reaction

must

involve some change to the oo ... ordinated ammonia so as to enable

it

to dimerise with another

ammonia to form a NN bonded group which can be degraded into co ... ordinated dlnltrogen~ /A possible reaction route could involve inter-mediates, similar to the nitrene { Ru(NH

3) 5 (NH)

J

a+,

40 said to

form during the acid degradation of ( Ru(NH

3) 5 (N3)

1

to give (Ru(NH₃) ₅ (N₂))

a+

and [ Ru₂ (NH₃) lO (N

2)

J

4

_+.