A series of mono- and dihydrido- as well as mono- and dimethylosmium(II) complexes containing [(mes)Os(CNR)] as a building block

The dihydridoosmium(II) complexes [(mes)OsH2(CNR)] (7–10) were prepared in excellent yield from the dichloroosmium(II) precursors [(mes)OsCl2(CNR)] upon treatment with 10% magnesium amalgam in THF in the presence of ethanol. Under similar conditions, the methylisocyanide derivative [(mes)OsH2(CNMe)] (6) as well as the monohydrido compounds [(mes)OsH(X)(CNMe)] (11, 13) were obtained. The same methodology using [(mes)OsCl(C6H5)(CNR)] as the starting material was applied for the preparation of the hydrido(phenyl)osmium(II) complexes [(mes)OsH(C6H5)(CNR)] (19–23) which were also isolated in almost quantitative yield. Treatment of these complexes with HCl in CH2Cl2 at −78°C led to the cleavage of the osmiumphenyl but not the osmiumhydride bond. Reactions of [(mes)OsCl2(CNR)] with MeLi/LiCl gave exclusively the dimethylosmium(II) compounds [(mes)Os(CH3)2(CNR)] (29–32) while the corresponding reactions with MeLi/LiI afforded a mixture of 29–32 and the monomethyl derivatives [(mes)OsI(Me)(CNR)] (26, 33–35). A cyclic carbeneosmium(II) complex 37 was obtained from [(mes)OsCl2(CNPh)] and MeLi/LiI followed by treatment with deactivated Al2O3. The etheneosmium(0) compound [(mes)Os(C2H4)(CNMe)] (38) was prepared from the dimethylosmium(II) precursor 29 and briefly investigated as starting material for photochemical CH activation reactions.