Osmacycles containing the {(Ph2PE)2N}− ligand (E=S or Se): synthesis and crystal structures

The reaction of (Ph2P)2NH (dppa) or Ph2PN(H)P(O)Ph2 (HL) with [Os(η6-cym)Cl2]2 [cym=p-CH3C6H4CH(CH3)2] in THF affords the orange, neutral mononuclear complexes [OsCl2(η6-cym)P-dppa] (1a) or [OsCl2(η6-cym)P-HL] (2), respectively, bearing a pendant PPh2 or P(O)Ph2 group. Complex 1a isomerises smoothly in CDCl3 solution to give the cationic P,P′-chelate complex [OsCl(η6-cym)P,P′-dppa]Cl (1b). Compound 2 can further be converted into the yellow P,O-chelate complexes [OsCl(η6-cym)P,O-HL][BF4] (3) and [OsCl(η6-cym)P,O-L] (4) [L=Ph2PNP(O)Ph2] upon treatment with either Ag[BF4] or tBuOK, respectively. Chloro bridge cleavage of [Os(η6-cym)Cl2]2 with the potassium salt of either {Ph2P(S)}2N− or {Ph2P(Se)}2N− yields the orange neutral complexes [OsCl(η6-cym){E,E′-Ph2P(E)}2N] (E=S 5, E=Se 6). All new compounds were characterised by a combination of NMR spectroscopy (1H and 31P{1H}), IR spectroscopy, microanalysis and X-ray crystallography. The five- (OsPNPO) and six-membered (OsEPNPE) osmacycles represent the first examples of crystallographically characterised osmium(II) metallocycles.