Gold(I) and related heterometallic derivatives of dimolybdenum complexes with asymmetric phosphinidene bridges

The phosphinidene-bridged complexes [Mo2Cp2(μ-κ(1):κ(1),η(6)-PR*)(CO)2] (1), [Mo2Cp2(μ-κ(1):κ(1),η(4)-PR*)(CO)3] (2), [Mo2Cp(μ-κ(1):κ(1),η(5)-PC5H4)(η(6)-HR*)(CO)2] (3), and [Mo2Cp2(μ-κ(1):κ(1)-PH)(η(6)-HR*)(CO)2] (4) were examined as precursors of heterometallic gold(I) and related derivatives (Cp = η(5)-C5H5, R* = 2,4,6-C6H2(t)Bu3). These complexes reacted with [AuCl(THT)] to give the corresponding derivatives [AuMo2ClCp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2], [AuMo2ClCp2(μ-κ(1):κ(1):κ(1),η(4)-PR*)(CO)3] (Au-Mo = 2.8493(6) Å), [AuMo2ClCp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)], and [AuMo2ClCp2(μ3-PH)(CO)2(η(6)-HR*)] formally resulting from the addition of an acceptor AuCl moiety to the short Mo-P bond of the parent substrates almost perpendicular to the corresponding Mo2P plane. The chloride ligand was easily displaced upon reaction of the PC5H4-bridged gold complex with K[MoCp(CO)3] to give the tetranuclear derivative [AuMo3Cp2(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)5(η(6)-HR*)] (Au-Mo = 2.711(2) and 2.807(2) Å). Compound 1 also reacted with HgI2 to give a hexanuclear complex [HgMo2Cp2(μ-I)I(μ-κ(1):κ(1),η(6)-PR*)(CO)2]2 containing dative Mo→Hg bonds (2.820(1) and 2.827(1) Å), whereas complex 3 gave the μ3-PR bridged complex [HgMo2CpI2(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)]. Complexes 1 to 4 also reacted easily with [AuL(THT)]PF6 (L = THT, P(p-tol)3, PMe3, P(i)Pr3) to give the corresponding cationic trinuclear derivatives [AuMo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2L](PF6) (Au-Mo = 2.8080(3) Å for L = P(p-tol)3), [AuMo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PR*)(CO)3L](PF6), and [AuMo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*){P(p-tol)3}](PF6). The blue, analogous PH-bridged complexes were more conveniently isolated as tetra-arylborate salts [AuMo2Cp2(μ3-PH)(CO)2(η(6)-HR*)L](BAr'4) (Au-Mo = 2.8038(6) Å for L = P(i)Pr3; Ar'= 3,5-C6H3(CF3)2]. Compounds 1, 3, and 4 reacted readily with the cation [Au(THT)2](+) (as PF6(-) or BAr'4(-) salts) in a 2:1 ratio to give respectively the corresponding pentanuclear derivatives [Au{Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2}2](PF6), [Au{Mo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)}2](PF6) (Au-Mo = 2.7975(7) and 2.8006(7) Å), and [Au{Mo2Cp2(μ3-PH)(CO)2(η(6)-HR*)}2](BAr'4) (Au-Mo = 2.8233(8) and 2.8691(7) Å). Related silver complexes were obtained from the reaction of 3 and 4 with [AgCl(PPh3)]4 after spontaneous symmetrization, while reaction of 1 with [Cu(NCMe)4]PF6 in a 2:1 ratio yielded the analogous copper complex [Cu{Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2}2](PF6). All the above cationic gold complexes having (μ-κ(1):κ(1):κ(1),η(6)-PR*) ligands (but not the copper complex) rearranged into [Au{Mo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)}2](PF6) in refluxing 1,2-dichloroethane solution.