Phosphine and phosphine oxide adducts of vanadium(IV) chloride: synthesis and structural studies

Abstract

The reaction products of VCl 4 with PEt 3, PMe 3, PMe 2Ph, Et 3PO and PhMe 2PO have been structurally characterized. Compound 1, [HPEt 3][VCl 4(PEt 3) 2], crystallizes in space group C2/ c with a=17.422(2), b=12.671(1), C=13.390(1) Å, β=95.76(2)°, V=2941(2) Å 3 and Z =4. The [VCl 4(PEt 3) 2] − anion has a trans arrangement of the phosphines with mean VCl and VP distances of 2.360(3) and 2.551(4) Å, respectively. Compound 2, mer-VCl 3(OPEt 3) 3, crystallizes in an orthorhombic cell ( P2 12 12 1) with a=13.310(4), b=17.754(6), c=12.383(3) Å, V=2926(2) Å 3 and Z=4; VCl distance (av.)=2.396(7) and VO (av.)=2.00(2) Å. Compound 3, mer-VCl 3(PMe 2Ph) 2(OPMe 2Ph) which has been reported before in a different space group, crystallizes with an orthorhombic ( Pmn2 1) unit cell: a=13.590(4), b=11.673(4), c=8.964(4) Å, V=1422(1) Å 3 and Z=2. A mirror plane bisects the molecule. The VCl, VP and VO distances are similar to those in 1 and 2. Compound 4, V 2Cl 6(PMe 3) 4, is a dinuclear compound which crystallizes with an orthorhombic unit cell ( Pna2 1) with cell dimensions: a=11.470(4), b=18.433(4), c=13.677(4) Å, V=2892(2) Å 3 and Z=4; distance VCl 1(av.)=2.30(1), VCl b(av.)=2.44(1) and VP(av.)=2.524(6) Å. The phosphines have the common 1,3,6,8 arrangement. The V···V distance of 3.691(2) Å is non-bonding. The reaction chemistry of these compounds is compared with that of the Nb and Ta analogs, and EPR measurements made on compound 1 are discussed. EPR spectra recorded for solutions of 1 in CH 2Cl 2 were shown to be due to about 1% of the vanadium in the form of VOCl 2(PEt 3) 2