Two Alternatives of Heteroallene Insertion in Metal — Ligand Bonds of Five‐Coordinate Ruthenium(II) and Osmium(II) Complexes [MXY(CO)(PiPr3)2]

The five‐coordinate chloro(hydrido)‐ and hydrido(iodo)ruthenium(II) and ‐osmium(II) compounds [MHX(CO)(PiPr3)2] (1, 2, 6, 7) react with CS2 to give the octahedral dithioformato complexes [MCl(CO)(PiPr3)2(η2‐S2CH)] (3, 4, 8, 9) in excellent yields. In the initial step, an addition of the heteroallene to the metal center occurs which is followed by insertion of CS2 into the M—H bond. On treatment of the dichlororuthenium(II) derivative [RuCl2(CO)(PiPr3)2] (10), which is prepared from RuCl3 · aq and PiPr3 in methanol, with carbon disulfide insertion into one of the Ru—PiPr3 bonds takes place to give the six‐coordinate ruthenium(II) complex 12 with zwitterion −S2CPiPr3+ as a chelating ligand. While the reaction of [OsH(SPh)(CO)(PiPr3)2] (13) with MeSCN leads to addition of the thionitrile to the metal center, the starting material reacts with MeNCS by insertion of the heteroallene into the Os—SPh bond to give two stereoisomers 15a, b, in which the nitrogen atom of the chelate ring is either cis or trans to the hydrido ligand. The octahedral methoxydithiocarbonato‐ and formatoosmium(II) compounds 16 and 17 are prepared from 2 and CS2 or CO2 in the presence of NaOMe. The crystal and molecular structures of 4 (M = Os), 12 and 15a have been determined.