Phosphine sigma-sydnonyl complexes of Ni, Pd, and Pt

3-R ' -4-Bromosydnones 1 (R ' = Me) and 2 (R ' = Ph) react with complexes M (PR3)(n) (M = Ni, Pd, Pt) to form mononuclear phosphine sigma -sydnonyl d(8 )-complexes of trans-configuration MBr(3-R ' -sydnon-4-yl)(PR3)(2): 3, 4 (M = Ni, R ' = Ph); 5 (M = Pd, R ' = Me); 6a (M = Pd, R ' = Ph); 7 (M = Pt, R ' = Ph), In the reaction of bromosydnone 2 with Pd(PPh3)(4), the cis-compl ex PdBr(3-Ph-sydnon-4-yl)(PPh3)(2) (6b) is formed initially; 6b rearranges in solution to give trans-complex 6a. On heating in THF, complex 6a is conv erted into the binuclear [PdBr(3-phenylsydnon-4-yl)(PPh3)](2) complex (8). The reaction of 4-chloromercurio-3-phenylsydnone (10) with Ni(PEt3)(4), Pd( PEt3)(4), and Pt(PPh3)(4) gives mononuclear NiCl(3-plieiiylsydtioii-4-yl)(P Et3)(2) complex (11), binuclear [PdCl(3-plienylsydnon-4-yl) (PPh3)](2) Comp lex (14), and cis- and trans-bi metallic PtCl(3-phenylsydnon-4-ylmercurio)( PPh3)(2) Complexes 15a and 15h, respectively. UV irradiation of 15a and 15h in a benzene solution induces redox demercuration to yield the PtCl((3-phe nylsydnon-4-ylcarbonyl)(PPh3)2 complex (16). In carbonylation of complexes 3, 6, and 7, CO insertion into the M-C bond occurred to form the correspond ing acyl derivatives MBr(3-phenylsydnon-4-ylcarbonyl)(PR3)(2) (17-19).