Restricted metal-arene and phosphorus-carbon bond rotation in (arene)Cr(CO)2L complexes (L = PPh3, P(o-tolyl)3)
作者:James A. S. Howell、Michael G. Palin、Patrick McArdle、Desmond Cunningham、Zeev Goldschmidt、Hugo E. Gottlieb、Daphna Hezroni-Langerman
DOI:10.1021/om00029a030
日期:1993.5
(1,4-Di-tert-butylbenzene)Cr(CO)2PPh3 exhibits restricted arene-Cr bond rotation in solution (DELTAG(double dagger)203 = 31.6 kJ mol-1). A series of (arene)Cr(CO)2P(o-tolyl)3 complexes have been prepared which exhibit restricted P-C rotation in solution; in cases where planar chirality is present, diastereoisomers may be observed which differ in the helicity of the exo2 phosphine conformation. Diastereoisomer interconversion and o-tolyl ring exchange occur with very similar activation energies. Crystal structure data: (1,4-di-tert-butylbenzene)Cr(CO)2PPh3, monoclinic, space group P2(1)/n, a = 10.137(1) angstrom, b = 13.992(2) angstrom, c = 20.882(3) angstrom, beta = 96.16(2)-degrees, Z = 4, R(w) = 9.18% for 345 refined parameters and 3643 observed reflections; (p-xylene)Cr(CO)2P(o-tolyl)3, monoclinic, space group P2(1)/n, a = 8.552(1) angstrom, b = 17.410(2) angstrom, c = 17.558(2) angstrom, beta = 91.95(2)-degrees, Z = 4, R(w) = 9.96% for 317 defined parameters and 3392 observed reflections; (benzene)Cr-(CO)2P(M-tolyl)3, monoclinic, space group P2(1)/n, a = 11.120(3) angstrom, b = 11.227(1) angstrom, c = 20.289(4) angstrom, beta = 100.63(2)-degrees, Z = 4, R(w) = 6.49% for 299 defined parameters and 3127 observed reflections.
(1,4-二叔丁基苯)[Cr(CO)₂PPh₃]在溶液中显示出受限的苯环-铬键旋转(ΔG‡(203) = 31.6 kJ·mol⁻¹)。一系列(arene)Cr(CO)₂P(o-tolyl)₃配合物已被制备,这些化合物在溶液中表现出受限的P-C键旋转;在存在平面手性的情况下,可能观察到非对映异构体,这些非对映异构体在exo²配位的磷配体构型的扭向性方面有所不同。非对映异构体的互变和o-tolyl环交换具有非常相似的活化能。晶体结构数据:(1,4-二叔丁基苯)Cr(CO)₂PPh₃,单斜晶系,空间群P2(1)/n,a = 10.137(1) Å,b = 13.992(2) Å,c = 20.882(3) Å,β = 96.16(2)°,Z = 4,R(w) = 9.18%(基于345个精修参数和3643个观测反射峰);(p-xylene)Cr(CO)₂P(o-tolyl)₃,单斜晶系,空间群P2(1)/n,a = 8.552(1) Å,b = 17.410(2) Å,c = 17.558(2) Å,β = 91.95(2)°,Z = 4,R(w) = 9.96%(基于317个定义参数和3392个观测反射峰);(benzene)Cr(CO)₂P(M-tolyl)₃,单斜晶系,空间群P2(1)/n,a = 11.120(3) Å,b = 11.227(1) Å,c = 20.289(4) Å,β = 100.63(2)°,Z = 4,R(w) = 6.49%(基于299个定义参数和3127个观测反射峰)。