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

Abstract

The reaction of (Ph 2P) 2NH (dppa) or Ph 2PN(H)P(O)Ph 2 (HL) with [Os(η 6-cym)Cl 2] 2 [cym= p-CH 3C 6H 4CH(CH 3) 2] in THF affords the orange, neutral mononuclear complexes [OsCl 2(η 6-cym) P-dppa] ( 1a) or [OsCl 2(η 6-cym) P-HL] ( 2), respectively, bearing a pendant PPh 2 or P(O)Ph 2 group. Complex 1a isomerises smoothly in CDCl 3 solution to give the cationic P, P′-chelate complex [OsCl(η 6-cym) P, P′-dppa]Cl ( 1b). Compound 2 can further be converted into the yellow P, O-chelate complexes [OsCl(η 6-cym) P, O-HL][BF 4] ( 3) and [OsCl(η 6-cym) P, O-L] ( 4) [L=Ph 2PNP(O)Ph 2] upon treatment with either Ag[BF 4] or t BuOK, respectively. Chloro bridge cleavage of [Os(η 6-cym)Cl 2] 2 with the potassium salt of either {Ph 2P(S)} 2N − or {Ph 2P(Se)} 2N − yields the orange neutral complexes [OsCl(η 6-cym){ E, E′-Ph 2P(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.