Dinuclear Copper(I) and Copper(I)/Silver(I) Complexes with Condensed Dithiolato Ligands

The Cu(III) complex Pr4N[Cu{S2C=(t-Bu-fy)}(2)] (1) (t-Bu-fy = 2,7-di-tert-butylfluoren-9-ylidene) reacts with [Cu(PR3)(4)]ClO(0)4 in 1:1 molar ratio in MeCN to give the dinuclear complexes [Cu-2{[SC=(t-Bu-fy)](2)S}(PR3)n] [n = 2, R = Ph (2a); n = 3, R = To (3b); To = p-tolyl]. The analogue of 2a with R = To (2b) can be obtained from the reaction of 3b with 1/8 equiv of S-8. Compound 2b establishes a thioketene-exchange equilibrium in solution leading to the formation of [Cu-4{S2C=(t-Bu-fy)}(2)(PTo(3))(4)] (4b) and [Cu-2{[SC=(t-Bu-fy)](3)S}(PTO3)(2)] (5b). Solid mixtures of 4b and 5b in varying proportions can be obtained when the precipitation of 2b is attempted using MeCN. The reactions of 1 with AgClO4 and PPh3, PTo(3) or PCy3 in 1:1:4 molar ratio in MeCN afford the heterodinuclear complexes [AgCu{[SC=(t-Bu-fy)](2)S}(PR3)(3)] [R = Ph (6a), To (6b), Cy (6c)]. Complex 6c dissociates PCy3 in solution to give the bis(phosphine) derivative [AgCu{[SC=(t-Bu-fy)](2)S)(PCy3)(2)] (7c), which undergoes the exchange of [M(PCy3)](+) units in CD2Cl2 solution to give small amounts of [Cu-2{[SC=(t-Bu-fy)](2)S}(PCy3)(2)] (2c) and [Ag-2{[SC=(t-Bu-fy)](2)S}(PCY3)(2)] (8c). Complexes 6a and b participate in a series of successive equilibria in solution, involving the dissociation of phosphine ligands and the exchange of [M(PCy3)](+) units to give 2a or 3b and the corresponding disilver derivatives {Ag-2{[SC=(t-Bu-fy)](2)S}(PR3)(2)] [R = Ph (8a), To (8b)], followed by thioketene-exchange reactions to give [AgCu{[SC=(t-Bu-fy)](3)S}(PR3)(2)] [R = Ph (9a), To (9b)]. Complexes 9a and b can be directly prepared from the reactions of 1 with AgClO4 and PPh3 or PTo(3) in 1:1:3 molar ratio in THF. The crystal structures of 3b, 6b, 6c, 7c, and 9a have been solved by single-crystal X-ray diffraction studies and, in the cases of 7c and 9a, reveal the formation of short Ag...Cu metallophilic contacts of 2.8157(4) and 2.9606(6) angstrom, respectively.