Binuclear (salen)osmium phosphinidine and phosphiniminato complexes

Abstract

The preparation of a number of binuclear (salen)osmium phosphinidine and phosphiniminato complexes using various strategies are described. Treatment of [Os^VI(N)(L¹)(sol)](X) (sol = H₂O or MeOH) with PPh₃ affords an osmium(IV) phosphinidine complex [Os^IV{N(H)PPh₃}(L¹)(OMe)](X) (X = PF₆1a, ClO₄1b). If the reaction is carried out in CH₂Cl₂ in the presence of excess pyrazine the osmium(III) phosphinidine species [Os^III{N(H)PPh₃}(L¹)(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 μ-oxo osmium(IV) phosphinidine complex is obtained, [(L¹){PPh₃N(H)}Os^IV–O–Os^IV{N(H)PPh₃}(L¹)](PF₆)₂3. Furthermore, if the reaction of [Os^VI(N)(L¹)(OH₂)]PF₆ with PPh₃ is done in the presence of 2, the μ-pyrazine species, [(L¹){PPh₃N(H)}Os^III–pz–Os^III{N(H)PPh₃}(L¹)](PF₆)₂4 can be isolated. Novel binuclear osmium(IV) complexes can be prepared by the use of a diphosphine ligand to attack two Os^VIN. Reaction of [Os^VI(N)(L¹)(OH₂)](PF₆) with PPh₂–CC–PPh₂ or PPh₂–(CH₂)₃–PPh₂ in MeOH affords the binuclear complexes [(MeO)(L¹)Os^IV{N(H)PPh₂–R–PPh₂N(H)}Os^IV(L¹)(OMe)](PF₆)₂ (R = CC 5, (CH₂)₃6). Reaction of [Os^VI(N)(L²)Cl] with PPh₂FcPPh₂ generates a novel trimetallic complex, [Cl(L²)Os^IV{NPPh₂–Fc–PPh₂N}Os^IV(L²)Cl] 7. The structures of 1b, 2, 3, 4, 5 and 7 have been determined by X-ray crystallography.