NEW COMPLEXES OF RHENIUM-(V) OR RHENIUM-(III) WITH VARIOUS DIPHOSPHINES OR BIS(DIPHENYLPHOSPHINO)METHANE MONOXIDE - CRYSTAL-STRUCTURE OF MER-[RECL3(DPPM-PP')(DPPOM-P)] [DPPM = PH2PCH2PPH2, DPPOM = PH2PCH2P(=O)PH2]

Treatment of [ReOCl3(AsPh3)2] or [ReOBr3(AsPh3)2] with the diphosphines, Ph2PCH2PPh2 (dppm), Ph2PC(= CH2)PPh2 (vdpp), cis-Ph2PCH = CHPPh2 (dppen), or Ph2PCHMePPh2 (1,1'-dppe) gave complexes of the type [ReOX3(L-L)] (L-L = chelating diphosphine, X = Cl or Br), in high yield. Treatment of [ReOCl3(AsPh3)2] with an excess of dppm at 20-degrees-C caused some reduction to give a mixture of two rhenium(III) complexes [ReCl3(dppm-PP')(dppom-P)] 2a [dppom = Ph2PCH2P(= O)Ph2] and [ReCl3(dppm-PP')(dppm-P)] 3a, which was difficult to separate. Treatment of [ReOCl3(AsPh3)2] with 2 mol of dppm in hot benzene gave pure 2a, whilst treatment of [ReCl3(NCMe)(PPh3)2] with 4-5 mol equivalents of dppm in hot benzene gave 3a in excellent yield. The tribromide analogue [ReBr3(dppm-PP')(dppom-P)] was prepared by heating [ReOBr3(dppm-PP')] with dppm. On treating [ReBr3(NCMe)(PPh3)2] with dppm, [ReBr3(dppm-PP')(dppm-P)] was formed but this was contaminated with the isomeric salt [ReBr2(dppm-PP')2]Br from which it could not be separated; however the NMR parameters for both components were assigned. The pure salt [ReBr2(dppm-PP')2]BPh4 was prepared from the mixture. In their H-1 NMR spectra, these rhenium(III) complexes show large paramagnetic shifts for the methylene protons of the chelated dppm and for some of the ortho-protons. Some of these resonances were assigned using two-dimensional correlation spectroscopy and nuclear Overhauser effect experiments. Crystals of complex 2a are monoclinic, space group P2(1)/n, with a = 1147.7(4), b = 2315.5(6), c = 2069.7(6) pm, beta = 91.76(3)-degrees and Z = 4; final R factor 0.0465 for 6150 observed reflections. The structure shows octahedral co-ordination with a mer arrangement of chlorines, a chelated dppm and a monodentate dppm monoxide, with the P = O group unco-ordinated.