Journal of Organometallic Chemistry vol:691 issue:19 pages:4058-4064
date:Univ Louvain, Dept Chem, B-3001 Heverlee, Belgium; Ecole Polytech, CNRS, URA 7653, DCPH,Lab Heteroelements & Coordinat, F-91128 Palaiseau, France
A novel cycloadduct of 1-boryl-3,4-dimethylphosphole was prepared by reaction of 3,4-dimethylphospholyl anion with monobromo-borane-methylsulfide complex (CH3)S (.) BH2Br at -60 degrees C. It was characterized as a six-membered trimer by spectroscopic means, and its structure confirmed by an X-ray crystal analysis and quantum chemical calculations. Density functional theory calculations (B3LYP) showed that the cyclic trimer is by far more stable than the monomer, dimers or open-chain forms. Various molecular and spectroscopic properties of the borylphosphole monomer and trimer were evaluated. In particular, the changes of the P-31 NMR chemical shifts upon oligomerization were examined. The six-membered ring was demonstrated to exist preferentially in a chair-like conformation. Computed NMR chemical shifts (H-1, C-13 and a lesser extent P-31) appear to be a highly sensitive analytical tool for distinguishing ring conformations having only small energy differences. (c) 2006 Elsevier B.V. All rights reserved.