LIGAND REDISTRIBUTION REACTIONS OF 5-COORDINATE D(6) SPECIES - RUHX(CO)P2, IRH2XP2, AND CP-ASTERISK-RUXP

For the species RuHXP2(CO), IrH2XP2, and CpRuXP (P = bulky phosphine, X = halide or pseudohalide), both homometallic halide exchange ([M]XP + [M]YP' reversible [M]YP + [M]XP') and heterometallic halide exchang e ([M]X + [M]'Y reversible [M]Y + [M]'X) are found to be quite rapid. In addition, hydride exchange occurs for RuHCl-(CO)P2 and RuDCl(CO)P'2 , as well as for IrH2Cl(PtBu2Ph)2 and IrD2Cl(PtBu2Me)2. Exchange is ge nerally faster for halides than for hydrides yet is much slower for th e groups phenoxide, OSiPh3, and C2Ph. These equilibria favor the bette r donating halide being bonded to the less electron-rich metal center. A variable-temperature H-1 NMR study of the degenerate exchange CpRu (PtBu2Me)Cl + CpRu'(PtBu2Me)Br reversible Cp*Ru(PtBu2Me)Br + Cp*Ru'-- (PtBu2Me)Cl establishes a second-order rate law with DELTAH(double-dag ger) = 8.6 +/- 0.8 kcal/mol and DELTAS(double-dagger) = -20 +/- 3 cal/ (mol K). These results clearly indicate the transient existence in sol ution of halide- and/or hydride-bridged dimers of monomeric metal comp lexes.