New complexes of rhenium-(V) or -(III) with various diphosphines or bis(diphenylphosphino)methane monoxide: crystal structure of mer-[ReCl3(dppm-PP′)(dppom-P)][dppm = Ph2PCH2PPh2, dppom = Ph2PCH2P(O)Ph2]

Publisher Website
Google Scholar
Abstract
Treatment of [ReOCl3(AsPh3)2] or [ReOBr3(AsPh3)2] with the diphosphines, Ph2PCH2PPh2(dppm), Ph2PC(CH2)PPh2(vdpp), cis-Ph2PCHCHPPh2(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°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 1H 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 P21/n, with a= 1147.7(4), b= 2315.5(6), c= 2069.7(6) pm, β= 91.76(3)° 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 PO group unco-ordinated.