Experimental and theoretical studies of correlated rotation in tris(ortho-tolyl) derivatives of P, As and Si

Abstract

Variable temperature N M R studies have established equilibrium constants and/or activation parameters for the exoz -exo3 equilibrium in the series M(o-tolyl), ( M = P, As), X M (o-tolyl), ( M = P, X = 0, S, Se; M = As, X = 0, S) and [MeM(o-tolyl),]"+ ( n = 0, M = Si; n = 1, M = P, As). The crystal structure of OAs(o-tolyl),H,O is reported. Molecular mechanics studies of P(o-tolyl), reproduce correctly the ground state ~X O , conformation and provide an analysis of the lowest energy two-ring flip exchange mechanism.t If a regular pyramid is constructed from the lp, 0, S, Se or Me as the apex and the three puru ring carbons as the base, a proximal (exo) substituent will point away from the base, while a distal (endo) substituent will point towards the base.

1H and 13C nuclear magnetic resonance studies of the conformational equilibrium of 2-(diphenylphosphino)benzaldehyde in polar and nonpolar solutions. Signs of the proximate coupling constants, 4J(CHO, 31P) and 3(13CHO, 31P)

“…The two relationships yield A as 3.2(3) and B as 8.8(3) Hz; the quoted errors are meant to indicate the concomitant ambiguities that may well include intrinsic solvent effects on ,J(H, P), see Table 2, as well as intrinsic substituent perturbations. That the latter are not very large, or at least roughly equal for CH, and CHO groups, is indicated by a recent report of ,J(H-~, P) as 4.4 Hz in tri(o-toly1)phosphine in solution (37). In the crystal, 8 values for this compound are close to those given for DPPB in Table 5.…”

“…NOW, for 4~(~-6 , P) the formyl substituent is at-P) values are 26.4 and 0.4 Hz, implying only small or similar perturbations by the methyl and formyl substituents. The avail6~o r example, for model calculations on geometry-optimized able evidence indicates the existence only of the exo conformer S T 0 3G MO structures of phenylphosphine, the INDO MO FPT of tri(o-toly1)phosphine in solution (2,37), that in which the three values of 3~(~, P) and 3~(~, P) are negative for all likely torsion methyl groups lie near the lone pair on phosphorus, that is, above angles (lone-pair directions with respect to the aromatic plane), the plane defined by the three carbon atoms bonded to phosphorus although for 'J(C, P) the numbers are qualitatively compatible (see 1).…”

Monoarylated Fluoromesitylpalladium Complexes

“…This reduces the rotation of the M−P−C ipso plane, thus also reducing the phosphane cone angle by ca. 35° 20…”

VOID: a PC program for the location and display of voids in crystal structures

“…A Fsx ®le for tris(o-tolyl)arsine oxide monohydrate (trPIFsx) is provided as an example (Howell et al, 1998). If a search for voids is made using the defaults, then none is found.…”