Facile pyramidal inversion at phosphorus in [R3EP7W(CO)(3)](2-) type complexes: An EXSY NMR study

摘要

A series of [R3EP7W(CO)(3)](2-) complexes where (E = Si, Ge, Sn, Pb; R = alkyl, phenyl) were prepared from [P7W(CO)(3)](3-) and R3EX reagents (X = Cl, Br) in dmf or CH3CN solutions. The Pb derivatives were prepared at -50 degrees C and are not thermally stable. The compounds were characterized by P-31 NMR spectroscopy and selected ESI-MS studies. All compounds undergo rapid inversion at the ER3-bound phosphorus atom. The barriers to inversion were measured by way of 2D P-31 EXSY experiments at various temperatures. The analysis showed very low barriers to pyramidal inversion (Delta G(double dagger) 10.3-13.5 kcal/mol) that were essentially enthalpic in origin. The activation barriers generally increased with increasing electronegativity of the E atom and the steric bulk of the ER3 substituents. The latter-Was interpreted by way of a non-linear transition state., (c) 2005 Elsevier B.V. All rights reserved.