Co-ordination chemistry of higher oxidation states. Part 35. Synthetic, spectroscopic, and electrochemical studies of some mer- and fac-[OsL3X3]/[OsL3X3]+ systems (L = PR3, AsR3, SbR3, or pyridine; X = Cl or Br): crystal structure of fac-[Os(PEt2Ph)3Cl3]·CH2Cl2

Abstract

The complexes mer-[OsL₃X₃](L = PMe₃,PEt₃, PEt₂Ph, PEtPh₂, or AsEt₃; X = Cl or Br) are oxidised by HNO₃–HBF₄ to mer-[OsL₃X₃]BF₄; fac- and mer-[Os(py)₃X₃]BF₄(py = pyridine) were obtained similarly, but attempts to oxidise fac-[OsL′₃Cl₃](L′= PR₃ or AsR₃) or mer-[Os(SbPh₃)₃X₃] to Os^IV failed. The osmium(IV) complexes were characterised by i.r., u.v.-visible, ³¹P n.m.r. spectroscopies, magnetic and conductance measurements, and their properties compared with those of the osmium(III) analogues. Cyclic voltammetry showed that most mer-[OsL₃X₃]^0/+ and the fac-[Os(py)₃X₃]^0/+ couples are electrochemically reversible, but fac-[OsL′₃Cl₃] exhibited only completely irreversible oxidation waves at highly positive potentials. The X-ray structure of fac-[Os(PEt₂Ph)₃Cl₃]·CH₂Cl₂ has been determined: space group P with a= 18.606(2), b= 10.088(2), c= 10.011 (4)Å;, α= 107.91 (3), β= 97.23(3), γ= 94.85(1)°, and Z= 2; Os–Cl 2.442(3)–2.449(2), Os–P 2.375(2)–2.380(3)Å.