Vanadium(II) alkyls. Synthesis and X-ray crystal structures of trans-VMe2(dmpe)2 and cis-V(CH2SiMe3) 2(dmpe)2

Robert J. Morris, Scott R. Wilson, Gregory S. Girolami

Research output: Contribution to journalArticlepeer-review

Abstract

Treatment of the vanadium(II) tetrahydroborate complex trans-V(η1-BH4)2(dmpe)2 with (trimethylsilyl) methyllithium gives the new vanadium(II) alkyl cis-V(CH2SiMe3)2(dmpe)2, where dmpe is the chelating diphosphine 1,2-bis(dimethylphosphino)ethane. Interestingly, this complex could not be prepared from the chloride starting material VCl2(dmpe)2. The CH2SiMe3 complex has a magnetic moment of 3.8 μB, and has been characterized by 1H NMR and EPR spectroscopy. The cis geometry of the CH2SiMe3 complex is somewhat unexpected, but in fact the structure can be rationalized on steric grounds. The X-ray crystal structure of cis-V(CH2SiMe3)2(dmpe)2 is described along with that of the related vanadium(II) alkyl complex trans-VMe2(dmpe)2. Comparisons of the bond distances and angles for VMe2(dmpe) 2, VC = 2.310(5) Å, VP = 2.455(5) Å, and PVP = 83.5(2)° with those of V(CH2SiMe3)2(dmpe)2, VC = 2.253(3) Å, VP = 2.551(1) Å, and P VP = 79.37(3)° show differences due to the differing trans influences of alkyl and phosphine ligands, and due to steric crowding in latter molecule. The VP bond distances also suggest that metal-phosphorus π-back bonding is important in these early transition metal systems. Crystal data for VMe2(dmpe)2 at 25°C: space group P21/n, with a = 9.041(1) Å, b = 12.815(2) Å, c = 9.905(2) Å, β = 93.20(1)°, V = 1145.8(5) Å3, Z = 2, RF = 0.106, and RwF =0.127 for 74 variables and 728 data for which I ≫ 2.58 σ(I); crystal data for V(CH2SiMe3)2(dmpe)2 at -75°C: space group C2/c, with a = 9.652(4) Å, b = 17.958(5) Å, c = 18.524(4) Å, β = 102.07(3)°, V= 3140(3) Å3, Z = 4, RF = 0.033, and RwF = 0.032 for 231 variables and 1946 data for which I ≫ 2.58 σ(I).

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalJournal of Organometallic Chemistry
Volume480
Issue number1-2
DOIs
StatePublished - Oct 18 1994

Keywords

  • Alkyls
  • Catalysis
  • Electron spin resonance
  • Phosphine
  • Vanadium
  • X-ray diffraction

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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