A Series of Neutral and Cationic Mesityleneosmium(II) Complexes Containing Bulky Phosphines with Various Functionalities as Ligands

Mono- and dihydridoosmium(II) compounds with [(mes)Os{iPr2P(CH2)nY}] (mes = mesitylene, 1,3,5-trimethylbenzene; n = 2, Y = NMe2, OMe; n = 3, Y = NMe2) as a molecular unit are prepared from the dichloro derivatives [(mes)OsCl2{iPr2P(CH2)nY}] and magnesium amalgam in THF in the presence of ethanol. Upon treatment of [(mes)Os(X)Cl{κ1(P)-iPr2P(CH2)2Y}] (X = H, Cl) with AgPF6 in CH2Cl2 cationic complexes with iPr2P(CH2)2Y as a chelating ligand are obtained. The compounds with Y = OMe react (for X = Cl) with L = CO and CNMe by opening of the chelate bond to give the PF6 salts [(mes)Os(L)Cl{κ1(P)-iPr2P(CH2)2Y}]PF6 and (for X = H) with KOtBu by fragmentation of the functionalized phosphine to afford the neutral complex [(mes)OsH(OMe)(iPr2PCHCH2)]. The reaction of the chelate compound [(mes)OsCl{κ2(P,O)-iPr2PCH2C(OMe)O}]PF6 with KOtBu leads to the formation of the corresponding uncharged phosphanyl ester enolate−osmium(II) complex by proton abstraction from the PCH2 unit. The ester enolate complex reacts with phen...