Mononuclear and dinuclear tertiary phosphine molybdenum complexes. oxo-molybdenum(IV), dinuclear Mo 2Cl 4L 4 and related derivatives

Abstract

Green and blue isomers of the oxo derivative MoOCl 2(PMe 3) 3 have been obtained by an oxygen-atom abstraction reaction between MoCl 4(thf) 2 and equimolar amounts of water in the presence of PMe 3. Methatesis with KX(X = NCO, NCS) yields MoOX 2(PMe 3) 3 and with NaS 2CNEt 2, MoO(S 2CNEt 2) 2(PMe 3). The latter complex readily loses PMe 3 to give MoO(S 2CNEt 2) 2 from which it can be prepared by addition of the phosphine ligand. Reaction of the blue purple complex, MoCl 3(thf) 3 ( I), with excess PMe 3 gives mer-MoCl 3(PMe 3) 3 which loses PMe 3 on heating in toluene to afford [MoCl 3(PMe 3) 2] 2. Reduction of ( I) with phosphines and zinc in tetrahydrofuran gives the dinuclear molybdenum(II) halide complexes Mo 2Cl 4L 4 (L = PMe 3, PEt 3, PhMe 2Ph, PEt 2Ph; L 2 = dppm), while Zn-acetic acid reduction yields Mo 2(CO 2Me) 4. Interaction of the chlorocarbonyl species MoCl 2(CO) 2(PMe 3) 3 with Tl(acac) affords Mo(acac)Cl(CO)(PMe 3) 3 which has an unusually low CO stretching frequency for a terminal carbonyl group (1755 cm −1).