Binuclear (salen)osmium phosphinidine and phosphiniminato complexes

The preparation of a number of binuclear (salen) osmium phosphinidine and phosphiniminato complexes using various strategies are described. Treatment of [Os-VI(N)(L-1)(sol)](X) (sol = H2O or MeOH) with PPh3 affords an osmium(IV) phosphinidine complex [Os-IV{N(H)PPh3}(L-1)(OMe)](X) (X = PF6 1a, ClO4 1b). If the reaction is carried out in CH2Cl2 in the presence of excess pyrazine the osmium(III) phosphinidine species [Os-III{N(H)PPh3}(L-1)(pz)](PF6) 2 can be generated. On the other hand, if the reaction is carried out in CH2Cl2 in the presence of a small amount of H2O, a mu-oxo osmium(IV) phosphinidine complex is obtained, [(L-1){PPh3N(H)}Os-IV-O-Os-IV {N(H)PPh3}(L-1)](PF6)(2) 3. Furthermore, if the reaction of [Os-VI(N)(L-1)(OH2)]PF6 with PPh3 is done in the presence of 2, the mu-pyrazine species, [(L-1){PPh3N(H)}Os-III-pz-Os-III {N(H)PPh3}(L-1)](PF6)(2) 4 can be isolated. Novel binuclear osmium(IV) complexes can be prepared by the use of a diphosphine ligand to attack two Os-VI N. Reaction of [Os-VI(N)(L-1)(OH2)](PF6) with PPh2-C C-PPh2 or PPh2-(CH2)(3)-PPh2 in MeOH affords the binuclear complexes [(MeO)(L-1)Os-IV {N(H)PPh2-R-PPh2N(H)} Os-IV(L-1)(OMe)](PF6)(2) (R = C C 5, (CH2)(3) 6). Reaction of [Os-VI(N)(L-2)Cl] with PPh(2)FcPPh(2) generates a novel trimetallic complex, [Cl(L-2)Os-IV {NPPh2-Fc-PPh2N}Os-IV(L-2)Cl] 7. The structures of 1b, 2, 3, 4, 5 and 7 have been determined by X-ray crystallography.