Dinuclear phosphido-bridged derivatives of platinum(I). Synthesis and characterization of [Pt2(m-PtBu2)2(PtBu2H)(L)] [L = PtBu2R (R = H, Li, n-Heptyl), CO, h2-CS2]

Contrarily to its palladium analogue, the platinum(II) dihydride [Pt(mu-PBu2t)(H)((PBu2H)-H-t)](2) (3) does not reductively eliminate molecular hydrogen to the corresponding Pt(I) dinuclear derivative. The transformation can, however, be achieved in a two-step procedure, i.e., by oxidant-induced hydride abstraction from 3, which produces the cationic monohydride [Pt-2(mu-PBu2t)(2)(H)((PBu2H)-H-t)(2)]PF6, (4)PF6, and deprotonation of the latter with a strong base, which produces the desired [Pt(mu-PBu2t)((PBu2H)-H-t)](2) (5). Complex 5 can be used as the precursor of other neutral bis-phosphido bridged platinum(I) derivatives. For example, carbon monoxide substitutes in mild conditions one of the terminally bonded secondary phosphines and yields quantitatively the monocarbonyl [Pt-2(mu-PBu2t)(2)((PBu2H)-H-t)(CO)], (6), whose crystal and molecular structure was determined by X-ray diffraction. Crystal data: monoclinic, space group P2(1)/n (No. 14), Z = 4, a = 9.0910(12) Angstrom, b = 30.527(4) Angstrom, c = 11.903(2) Angstrom, beta = 93.78(2)degrees, R(F-o) = 0.0378, Rw(F-o(2)) = 0.0826 [I > 2 sigma(I)]. Complex 6 reacts cleanly with carbon disulfide to give the product of CO substitution [Pt-2(mu-PBu2t)(2)((PBu2H)-H-t)(eta-CS2)] (9) Further modifications of complex 5 can be achieved by deprotonating with n-BuLi/TMEN one of its secondary phosphines, which produces the lithiated derivative [Pt-2(mu-PBu2t)(2)((PBu2H)-H-t)((PBu2Li)-Li-t)] (10). The latter has been alkylated with 1-bromoheptane to the soluble derivative [Pt-2(mu-PBu2t)(2)((PBu2H)-H-t)((PBu2R)-R-t)] (12) (R = n-heptyl).