Reactions of diphenylphosphine and methyldiphenylphosphine with (?3-allyl)dicarbonylchlorobis(methyl cyanide)molybdenum and-tungsten: Mechanistic implications in the reductive elimination of allyl halides

Electron spin resonance and photoelectron studies of neutral bis(.eta.-arene)metal compounds (metal = Ti, V, Nb, Ta, Mo, and W)

“…(1) (where is the separation between the ax and unoccupied ex levels). 4 The values of g± decrease slightly down the group (M = Cr, Mo, W),9 although not nearly as much as expected from changes in X alone. The signs of the chromium hyperfine coupling (Cr(77-C6H6)2+) are consistent with occupation of the d2z orbital, and Aiao is deduced to originate in spin polarization with no significant 3d2a/4s mixing.7 Wide-line nuclear magnetic resonance has been used to deduce that the proton hyperfine coupling constants of Cr(?7-C6H6)2+ and V(tj-C6H6)2 have positive signs, while the coupling constants of the methyl protons in substituted M(7?-arene)2 complexes are negative.7,10 The large positive value of AH (ring) has been explained by dominant delocalization arising by mixing of the and 7r(alg) ring orbitals assisted by some spin polarization.…”

“…facilitate understanding of the underlying causes of trends, we have carried out a ligand field analysis of the ion states using the expressions given below. 4 The e2/a1 splitting is given by functions of A2 (see Scheme I), B and C. The Racah parameters, B and C, are measures of electron repulsion within the d shell. In deriving these expressions, we have assumed that C…”