PREPARATION, PROPERTIES AND REACTIVITY OF METAL HETEROCYCLES .73. BEHAVIOR OF MONOMERIC AND DIMERIC THIOPHOSPHONITONICKEL COMPLEXES WITH ALKYNES AND PHOSPHAALKYNES

Depending on the steric demand of the phosphorus bound substituents, the action of the secondary phosphine sulphides R2P(H)S (1a-h) (R = Me (a), Et (b), (i)Pr (c), (t)Bu (d), Ph (e), Xyl (f), Mes (g), Cy (h)) on nickelocene results in the formation of either the dimeric complexes [(eta-5-C5H5)Ni(mu-S=PR2)]2 (2a-c,e,h) or the monomeric thiophosphinito complexes (eta-5-C5H5)Ni(eta-2-S=PR2) (3d,f,g). The transition monomer --> dimer occurs between R = Cy and (t)Bu. In addition to 3d,f,g, the mixed ligand complexes (R2PS2)Ni(eta-2-S=PR2) (4d,f,g) are formed. H3CO2CC=CCO2CH3 cyclo-codimerizes with the P=S function in the xylyl and mesityl compounds 3f,g with formation of the S-isomeric thiaphosphanickelacyclopentadienes (eta-5-C5H5)NiS=P(R2)C(CO2Me)=C(CO2Me) (5f,g). By way of contrast with the phosphaalkyne tBuC=P the P=S bond in 3f,g is cleaved for the first time with formation of the novel thiadiphosphanickelacyclopentenes (eta-5-C5H5)NiSC((t)Bu)=PPR2 (6f,g). According to an X-ray structural analysis the planar five-membered heterocycle 6f crystallizes in the triclinic space group P1BAR with Z = 2, and has short P-C and C-S distances.