Sohnlein Bradford R, Yang Dong-Sheng
Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA.
J Chem Phys. 2006 Apr 7;124(13):134305. doi: 10.1063/1.2186307.
Group 6 metal bis(benzene) sandwich complexes (M-bz(2): M=Cr, Mo, and W and bz=C(6)H(6)) were produced with laser vaporization molecular beam techniques and studied by pulsed-field ionization zero electron kinetic energy spectroscopy and density functional theory calculations. Each sandwich complex is in a D(6h) eclipsed configuration with (1)A(1g) and (2)A(1g) as the neutral and cationic ground electronic states, respectively. The adiabatic ionization energies for Cr-, Mo-, and W-bz(2) are measured to be 44,081(7), 44,581(10), and 43,634(7) cm(-1), respectively. The metal-benzene stretch and benzene torsion frequencies of the ion are measured to be 264, 277, and 370 cm(-1) and 11, 21, and 45 cm(-1) for Cr-, Mo-, and W-bz(2), respectively. In addition, a C-H out-of-plane bending mode is measured to be 787 cm(-1) for the Cr(+)-bz(2) complex, while a C-C in-plane bending mode is measured to be 614 cm(-1) for the W(+)-bz(2) complex. The unusual trend in the ionization energy and metal-benzene stretch frequency indicates strong relativistic effects on tungsten binding.
通过激光汽化分子束技术制备了第6族金属双（苯）夹心配合物（M-bz₂：M = Cr、Mo和W，bz = C₆H₆），并采用脉冲场电离零电子动能光谱和密度泛函理论计算对其进行了研究。每个夹心配合物都处于D₆h重叠构型，其中（¹A₁g）和（²A₁g）分别为中性和阳离子基态电子态。测得Cr-bz₂、Mo-bz₂和W-bz₂的绝热电离能分别为44081(7)、44581(10)和43634(7) cm⁻¹。对于Cr-bz₂、Mo-bz₂和W-bz₂，离子的金属-苯伸缩频率和苯扭转频率分别测得为264、277和370 cm⁻¹以及11、21和45 cm⁻¹。此外，对于Cr⁺-bz₂配合物，测得一个C-H面外弯曲模式为787 cm⁻¹，而对于W⁺-bz₂配合物，测得一个C-C面内弯曲模式为614 cm⁻¹。电离能和金属-苯伸缩频率的异常趋势表明相对论效应在钨键合中起了重要作用。
