Synthesis and characterisation of WVI complexes of phosphane oxide ligands, [WO2X2(OPR3)2] (X = F, Cl or Br; R = Me or Ph), and of the [MoO2F2(OPR3)2]

Phosphane oxide complexes of dioxidotungstenVI, [WO2X2(OPR3)2] (X = Cl or Br, M = Ph or Me) have been prepared under anhydrous conditions from the reaction of WX6 with (Me3Si)2O in CH2Cl2, followed by addition of OPR3. Some diphosphane dioxide analogues have been made similarly, viz, [WO2X2(L-L)] {L-L = Ph2P(O)(CH2)nP(O)Ph2 (n = 1 or 2), o-C6H4[P(O)Ph2]2}. The complexes have been characterised by elemental analysis, IR and NMR (1H and 31P{1H}) spectroscopy, and the structures of [WO2Br2(OPPh3)2] and [WO2Cl2(OPMe3)2] determined, revealing distorted six-coordinate tungsten centres with cis-WO2 and trans-WX2 units. The difluorido-dioxido complexes [MO2F2(OPR3)2] (M = Mo or W) and [WO2F2(L-L)] (L-L = 2,2-bipyridyl, 1,10-phenanthroline) have been prepared by fluorination of the corresponding chlorido complexes with Me3SnF in CH2Cl2. These are characterised similarly and by 19F{1H} NMR spectroscopy. Attempts to make [MO2I2(OPR3)2] were unsuccessful. No adduct formation occurs between CrO2Cl2 and OPPh3 under rigorously anhydrous conditions. Crystal structures of [Me3SnCl(OPPh3)] and two forms of [WO2Cl2(1,10-phen)] are also reported and discussed