Copper(I)-Halide Complexes

A search of the CSD for dihalide copper complexes with phosphine/thioether ligand(s) resulted in 20 hits. Almost all of the results were binuclear copper complexes with bridging halide ions. Most of the complexes contained two separate ligand donors, triphenylphosphine (or a close derivative) and a thiourea alkyl chain (S=C(NH2)(NHR)), of which most have been reported

by Lobana et al. There is only one example where the phosphine/thioether donors

are on a single backbone. It is a binuclear, dichloride-bridged complex with a ferrocene based backbone (Figure 7-7).14,15

Of the 20 search results, there were four chloride, six bromide, and ten iodide complexes; however, there are only two halide series. The first example is a polymeric chain, which contains a bridging P/S ligand between the two copper metal centers, forming a six-membered (S-P-Cu) ring (Figure 7-8).16 The second contains two separate phosphorus/sulfur ligands of triphenyl phosphine and acetophenone thiosemicarbazone (Figure 7-8).17 The chloride and bromide complexes (with these ligands) are structurally identical, but in the iodide case, the sulfur ligand forms a third bridge between the metal centers.

P S Cu Cl Cl Cu P S Fe Fe

Figure 7-7. The only example of a Cu(I)-X2 complex with a single P/S-

containing ligand.

We have used 7.1 as a ligand in a series of binuclear Cu(I)-halide complexes. These complexes have the standard formula [(7.1)Cu(µ-X)2Cu(7.1)];

where X = Cl (7.6), Br (7.7), or I (7.8) (Figure 7-9). These copper complexes all

132 P S Cu P S Cu EtS EtS Et SEt SEt Et X X n P Cu X X Cu H₂N NH S N P NH2 HN S N H₃C CH₃

Figure 7-8. Examples of Cu(I)-dihalide series. Left drawing depicts a polymeric structure with a P/S bridging ligand (X = Cl, Br, or I). Right

drawing depicts the ligands triphenyl phosphine and acetophenone thiosemicarbazone (X = Cl or Br).

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crystallize in very similar (P-1) triclinic unit cells with an inversion center that

lies in the middle of the complex (Figure 7-10). The R1 factors for 7.6, 7.7, and

7.8 are 8.57%, 8.58%, and 6.84%, respectively. Appendix 1 includes refinement data. P S Cu X X P S Cu X = Cl (7.6), Br (7.7), or I (7.8)

Figure 7-9. Binuclear copper(I) complexes of 7.1.

7.4.1. Metal Center Environment

Each Cu(I) metal center is pseudo-tetrahedral and is ligated by the bidentate P/S ligand (7.1) and two bridging halide anions. Table 7-5 shows bond distances and angles around the metal centers in these complexes. The overall binuclear complexes are formed by two Cu(I) metal ions each containing a ligand linked by the two bridging halogen anions.

Surprisingly, the Cu…Cu distance in these complexes decreases as the halide ion size increases. In 7.6, the Cu(1)…Cu(1)’ distance is 3.0037(13) Å, which is greater than 7.7 (2.9296(14) Å) > 7.8 (2.8568(11) Å). However, the X(1)…X(1)’ distance increases as the halide ions increase. In 7.6, this distance is 3.744(2) Å < 7.7 (3.9193(14) Å < 7.8 (4.3287(8) Å). The result of this is an elongation of the diamond-shaped core of the complexes along the X-X’ axis as the size of the halogen ion increases.

As expected, the Cu(1)-X(1) and the Cu(1)-X(1)’ bond distances increase as the halide size increases, however, there is some asymmetry, as the Cu(1)-X(1) distance is slightly shorter than the Cu(1)-X(1)’ bond distance in all cases. The

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Cu(1)-P(1) bond distances are similar ranging from 2.217(2) Å to 2.248(2) Å and the Cu(1)-S(1) distances are also similar and range from 2.442(2) Å to 2.487(2) Å.

Table 7-5. Selected bond lengths (Å) and angles (°) for 7.1, 7.6, 7.7, and 7.8. 7.1 7.6 7.7 7.8 Cu(1)…Cu(1)’ 3.0037(13) 2.9296(14) 2.8568(11) X(1)…X(1)’ 3.744(2) 3.9193(14) 4.3287(8) Cu(1) - X(1) 2.3889(17) 2.4301(14) 2.5809(11) Cu(1) - X(1)’ 2.411(2) 2.4630(16) 2.6055(12) Cu(1) - P(1) 2.222(2) 2.217(2) 2.248(2) Cu(1) - S(1) 2.487(2) 2.442(2) 2.444(2) Cu(1)-X(1)-Cu(1)’ 77.48(6) 73.55(4) 66.85(3) X(1)-Cu(1)-X(1)’ 102.52(6) 106.45(4) 113.15(3) P(1)-Cu(1)-X(1) 127.97(7) 126.62(8) 125.01(7) P(1)-Cu(1)-X(1)’ 120.62(8) 116.52(9) 113.00(7) S(1)-Cu(1)-X(1) 108.34(7) 108.47(7) 106.70(6) S(1)-Cu(1)-X(1)’ 113.14(6) 113.12(7) 112.15(6) P(1)-Cu(1)-S(1) 81.51(7) 82.89(7) 81.52(7) Mean Plane Deviations P(1) 0.018(5) -0.199(9) -0.196(10) -0.090(9) S(1) 0.136(5) 0.101(9) 0.112(10) 0.186(9) Cu(1) -1.616(11) -1.566(12) 1.594(11)

1_{X = Cl for 7.6, Br for 7.7, or I for 7.8.}

As implied by the “elongating diamond” above, the Cu(1)-X(1)-Cu(1)’ angle decreases as the halide ion size increases, so 7.6 (77.48(6)°) > 7.7 (73.55(4)°) > 7.8 (66.85(3)°). Correspondingly, the X(1)-Cu(1)-X(1)’ angle distinctly increases from 7.6 (102.52(6)°) < 7.7 (106.45(4)°) < 7.8 (113.15(3)°). The P(1)-Cu(1)-S(1) bond angle is ~82° in all three complexes.

7.4.2. Ligand Environment

The P(1)…S(1) distance of 7.1, when bound to the copper center, is larger than in uncoordinated 7.1. Table 7.6 shows a comparison of bond distances and angles of the coordinated and uncoordinated ligand. The P(1)…S(1) distance in these complexes ranges from 3.067(2) Å (7.8) to 3.089(3) Å (7.7; 7.6 is 3.081(2) Å). Conversely, the P(1)-C(1) bond distances of 7.1 and 7.6-7.8 are identical

within error. Additionally, the S(1)-C(9) bond distances in 7.6-7.8 range from 1.796(8) Å to 1.812(8) Å, which is larger than 7.1 and increases with 7.6 < 7.8 < 7.7.

Table 7-6. Selected bond lengths (Å) and angles (°) for 7.1, 7.6, 7.7, and 7.8. 7.1 7.6 7.7 7.8 P(1)…S(1) 3.0339(13) 3.081(2) 3.089(3) 3.067(2) P(1) - C(1) 1.850(3) 1.844(7) 1.837(8) 1.847(8) S(1) - C(9) 1.784(3) 1.796(8) 1.812(8) 1.805(8) P(1)-C(1)-C(2) 118.0(2) 116.7(5) 116.6(5) 116.6(5) P(1)-C(1)-C(10) 124.1(2) 124.7(5) 124.1(6) 124.1(6) S(1)-C(9)-C(8) 115.1(2) 118.1(6) 116.9(6) 117.1(6) S(1)-C(9)-C(10) 123.8(2) 121.9(5) 121.4(5) 121.1(5) C(2)-C(1)-C(10) 117.8(3) 118.4(7) 119.1(7) 119.1(7) C(10)-C(9)-C(8) 121.0(3) 119.8(7) 121.5(7) 121.8(7) C(1)-C(10)-C(9) 126.4(3) 127.3(7) 129.0(7) 129.1(7) C(4)-C(5)-C(10)-C(1) -1.2(4) 1.6(11) -0.6(12) -0.2(8) C(6)-C(5)-C(10)-C(9) 0.1(3) -1.5(11) -0.2(9) 0.3(8) C(4)-C(5)-C(10)-C(9) -179.5(3) 179.8(6) 179.7(7) -179.0(7) C(6)-C(5)-C(10)-C(1) 178.5(3) -179.7(7) 179.4(8) 179.0(7) Mean Plane Deviations P(1) 0.018(5) -0.199(9) -0.196(10) -0.090(9) S(1) 0.136(5) 0.101(9) 0.112(10) 0.186(9) Cu(1) -1.616(11) -1.566(12) 1.594(11)

1_{X = Cl for 7.6, Br for 7.7, or I for 7.8.}

The outer P(1)-C(1)-C(2) angle is ~1° smaller in 7.6-7.8 than in 7.1, however the inner angle P(1)-C(1)-C(10) is almost identical in 7.1 and 7.6-7.8. The outer S(1)-C(9)-C(8) angle increases through the range 116.9(6)° to 118.1(6)°, where 7.7 < 7.8 < 7.6. The smallest of these angles is ~2° larger than in 7.1. Finally, the inner S(1)-C(9)-C(10) angle in 7.1 (123.8(2)°) is larger than in 7.6 - 7.8 (~121°).

The out-of-plane deviations of P(1) are most distorted in 7.6 and 7.7, being -0.199(9) Å and -0.196(10) Å from the naphthalene plane, respectively. P(1) in 7.1 deviates 0.018(5) Å from the plane compared to only -0.090(9) Å in 7.8. The out-of-plane deviation of S(1) in 7.1 (0.136(5) Å), is within the range defined by

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the copper-halide complexes, where 7.6 (0.101(9) Å) < 7.7 (0.112(10) Å) < 7.8 (0.186(9) Å). The Cu(1) sits ~1.6 Å out of the naphthalene plane in all three complexes.

Overall, in the copper complexes, the distortions of the angles near the

peri-positions in the naphthalene backbone are minor and compare quite closely

to the distortions in free (uncomplexed) 7.1. However, the inner ring torsion angles in 7.6-7.8 are, for the most part, less distorted than in 7.1.