John Kevin D., Miskowski Vincent M., Vance Michael A., Dallinger Richard F., Wang Louis C., Geib Steven J., Hopkins Michael D.
Departments of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and Wabash College, Crawfordsville, Indiana 47933.
Inorg Chem. 1998 Dec 28;37(26):6858-6873. doi: 10.1021/ic980866u.
The nature of the skeletal vibrational modes of complexes of the type M(2)(C&tbd1;CR)(4)(PMe(3))(4) (M = Mo, W; R = H, Me, Bu(t)(), SiMe(3)) has been deduced. Metrical data from X-ray crystallographic studies of Mo(2)(C&tbd1;CR)(4)(PMe(3))(4) (R = Me, Bu(t)(), SiMe(3)) and W(2)(C&tbd1;CMe)(4)(PMe(3))(4) reveal that the core bond distances and angles are within normal ranges and do not differ in a statistically significant way as a function of the alkynyl substituent, indicating that their associated force constants should be similarly invariant among these compounds. The crystal structures of Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) and Mo(2)(C&tbd1;CBu(t)())(4)(PMe(3))(4) are complicated by 3-fold disorder of the Mo(2) unit within apparently ordered ligand arrays. Resonance-Raman spectra ((1)(delta-->delta) excitation, THF solution) of Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) and its isotopomers (PMe(3)-d(9), C&tbd1;CSiMe(3)-d(9), (13)C&tbd1;(13)CSiMe(3)) exhibit resonance-enhanced bands due to a(1)-symmetry fundamentals (nu(a) = 362, nu(b) = 397, nu(c) = 254 cm(-)(1) for the natural-abundance complex) and their overtones and combinations. The frequencies and relative intensities of the fundamentals are highly sensitive to isotopic substitution of the C&tbd1;CSiMe(3) ligands, but are insensitive to deuteration of the PMe(3) ligands. Nonresonance-Raman spectra (FT-Raman, 1064 nm excitation, crystalline samples) for the Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) compounds and for Mo(2)(C&tbd1;CR)(4)(PMe(3))(4) (R = H, D, Me, Bu(t)(), SiMe(3)) and W(2)(C&tbd1;CMe)(4)(PMe(3))(4) exhibit nu(a), nu(b), and nu(c) and numerous bands due to alkynyl- and phosphine-localized modes, the latter of which are assigned by comparisons to FT-Raman spectra of Mo(2)X(4)L(4) (X = Cl, Br, I; L = PMe(3), PMe(3)-d(9))(4) and Mo(2)Cl(4)(AsMe(3))(4). Valence force-field normal-coordinate calculations on the model compound Mo(2)(C&tbd1;CH)(4)P(4), using core force constants transferred from a calculation on Mo(2)Cl(4)P(4), show that nu(a), nu(b), and nu(c) arise from modes of strongly mixed nu(Mo(2)), nu(MoC), and lambda(MoCC) character. The relative intensities of the resonance-Raman bands due to nu(a), nu(b), and nu(c) reflect, at least in part, their nu(M(2)) character. In contrast, the force field shows that mixing of nu(M(2)) and nu(C&tbd1;C) is negligible. The three-mode mixing is expected to be a general feature for quadruply bonded complexes with unsaturated ligands.
已推断出M(2)(C≡CR)(4)(PMe(3))(4) 类型配合物（M = Mo、W；R = H、Me、Bu(t)、SiMe(3)）的骨架振动模式的性质。对Mo(2)(C≡CR)(4)(PMe(3))(4) （R = Me、Bu(t)、SiMe(3)）和W(2)(C≡CMe)(4)(PMe(3))(4) 进行X射线晶体学研究得到的度量数据表明，核心键长和键角在正常范围内，并且作为炔基取代基的函数，在统计学上没有显著差异，这表明它们相关的力常数在这些化合物中应同样不变。Mo(2)(C≡CSiMe(3))(4)(PMe(3))(4) 和Mo(2)(C≡CBu(t))(4)(PMe(3))(4) 的晶体结构因Mo(2)单元在明显有序的配体阵列中的三重无序而变得复杂。Mo(2)(C≡CSiMe(3))(4)(PMe(3))(4) 及其同位素异构体（PMe(3)-d(9)、C≡CSiMe(3)-d(9)、(13)C≡(13)CSiMe(3)）的共振拉曼光谱（(1)(δ→δ)激发，THF溶液）显示出由于a(1)对称基频（对于天然丰度配合物，ν(a) = 362、ν(b) = 397、ν(c) = 254 cm(-1)）及其泛音和组合而产生的共振增强带。基频的频率和相对强度对C≡CSiMe(3)配体的同位素取代高度敏感，但对PMe(3)配体的氘代不敏感。Mo(2)(C≡CSiMe(3))(4)(PMe(3))(4) 化合物以及Mo(2)(C≡CR)(4)(PMe(3))(4) （R = H、D、Me、Bu(t)、SiMe(3)）和W(2)(C≡CMe)(4)(PMe(3))(4) 的非共振拉曼光谱（FT-拉曼，1064 nm激发，晶体样品）显示出ν(a)、ν(b)和ν(c)以及由于炔基和膦定位模式产生的许多谱带，通过与Mo(2)X(4)L(4) （X = Cl、Br、I；L = PMe(3)、PMe(3)-d(9)）(4) 和Mo(2)Cl(4)(AsMe(3))(4) 的FT-拉曼光谱比较对后者进行了归属。使用从对Mo(2)Cl(4)P(4) 的计算转移的核心力常数，对模型化合物Mo(2)(C≡CH)(4)P(4) 进行价力场正则坐标计算表明，ν(a)、ν(b)和ν(c)源于具有强烈混合的ν(Mo(2))、ν(MoC)和λ(MoCC)特征的模式。由于ν(a)、ν(b)和ν(c)产生的共振拉曼谱带的相对强度至少部分反映了它们的ν(M(2))特征。相比之下，力场表明ν(M(2))和ν(C≡C)的混合可以忽略不计。对于具有不饱和配体的四重键配合物，这种三模式混合预计是一个普遍特征。
