Halfsandwich-Type Osmium Complexes Containing Phosphanylmethanide and Phosphanyl Alcoholate Anions as Bidentate Ligands

The mononuclear dichloroosmium(II) complexes [(mes)‐Os(L)Cl2] (2‐5) with the phosphanyl ether L = iPr2PCH2‐CH2OMe and phosphanyl esters L = IPr2P(CH2)nCO2R as ligands are obtained from [(mes)OsCl2]n and L in almost quantitative yield. While compound 3 (L = iPr2PCH2CH2CO2Me) reacts with Mg/Hg in THF in the presence of ethanol to give the monohydrido derivative 6, treatment of 4 (L = iPr2PCH2‐CO2Me) or 5 (L = iPr2PCH2CO2Et) with Al2O3/NaH in THF yields the phosphanylmethanide complexes [(mes)‐Os{k2(P,C)‐iPr2PCHCO2R}Cl] (7, 8). In contrast to the reaction of 4 with Mg/Hg in THF/EtOH which yields the dihydrido compound [(mes)OsH2{k(P)‐iPr2PCH2CO2Me}] (10), the corresponding reaction of 4 with excess PhMgBr does not lead to an OsPh2 species but instead gives the new chelate complex [(mes)OsPh{k2(P,O)‐iPr2PCH2CPh2O}] (11). The crystal and molecular structures of 7 and 11 were determined.