Reactivity of substituted thiophenes toward tris(triethylphosphine)platinum(0), -palladium(0), and -nickel(0)

The reactions of [M(PEt3)(3)] (M = Pt (1), Pd (2), Ni (3)) with 3-chlorothi ophene, 2-chlorothiophene, 3-nitrothiophene, 2-nitrothiophene, 2-methoxythi ophene, 3-methoxythiophene, 2-acetylthiophene, and 3-acetylthiophene afford ed thiaplatinacycles of the type [(Et3P)(2)M-(C,S-C4H3RS)], (for M = Pt, R = Cl (4 and 5), NO2 (6 and 7), MeO (8 and 9), Ac (10 and 11); for M = Pd, R = Cl (12 and 13), NO2 (14), MeO (15 and 16), Ac (17 and 18), for M = Ni, R = Cl (19)). When 3 and 2-chlorothiophene were reacted, another compound re sulting from the oxidative addition of the C-Cl bond could be isolated, wit h the formulation [(Et3P)(2)Ni-(Cl)(eta (1)-T)] (20). Additionally the reac tion of 3 with 2-nitrothiophene produced a compound derived from a C-H acti vation reaction, [(Et3P)(2)Ni(H)(eta (1)-NO2T)] (21). The thiaplatinacycles 8-11 were shown to be active intermediates in HDS reactions, under catalyt ic conditions, to give 81 cycles at 300 psi, 100 degreesC in THF, in the pr esence of metallic mercury. Crystal structures are reported for 4 and 7.