Treatment of TiCl3(thf)3(thf = tetrahydrofuran) with the chelating phosphine 1,2-bis(diisopropylphosphino)ethane (dippe) gives two products: the purple dimer [TiCl3(dippe)]2and the green monomer TiCl3(dippe)(thf). The two compounds may be readily interconverted by loss or addition of the thf ligand. The dimer is coupled antiferromagnetically, and its X-ray crystal structure reveals an octahedral geometry about each titanium(III) center and a Ti…Ti distance of 3.44 Å. The dippe ligands each chelate a titanium atom and are trans to the bridging chlorides; the dimer thus possesses approximate D2hsymmetry. Reactions of MCl3(thf)3, where M is vanadium or chromium, with dippe yield the monomeric thf adducts MCl3(dippe)(thf). The bromo-vanadium analogue VBr3(dippe)(thf) and the chromium acetonitrile adduct CrCl3(dippe)(MeCN) are also described. Addition of dippe to CrMeCl2(thf)3gives the chromium(III) alkyl CrMeCl2(dippe)(thf) which has been shown to be a slow ethylene polymerization catalyst at room temperature. NMR and EPR studies of the dippe adducts are described. Crystal data for [TiCl3(dippe)]2·PhMe: orthorhombic, space group Pbcn, with a = 15.586 (5) Å, b = 14.442 (4) Å, c = 21.639 (6) Å,V = 4871 (2) Å3, Z = 4, RF= 6.4%, RwF= 6.6% for 196 variables and 1231 data with I > 2.58σ(I).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry