Ricks Allen M, Reed Zach D, Duncan Michael A
Department of Chemistry University of Georgia, Athens, Georgia 30602, USA.
J Am Chem Soc. 2009 Jul 8;131(26):9176-7. doi: 10.1021/ja903983u.
Gas-phase metal carbonyl cations of the vanadium-group metals (V(+), Nb(+), Ta(+)) were produced in a molecular beam by laser vaporization and then mass-analyzed and size-selected in a time-of-flight spectrometer and studied with IR laser photodissociation spectroscopy in the carbonyl-stretching region. The abundances in the mass spectra, the fragmentation patterns, and the IR spectra provided a combined approach that revealed the coordination numbers in these systems. Although seven-coordinate structures would have 18 electrons in each case, V(CO)(6)(+) was found to be formed rather than V(CO)(7)(+). Nb(+) formed both six- and seven-coordinate species, while Ta(+) formed only the Ta(CO)(7)(+) complex. Density functional theory computations were used to predict the IR spectra for these systems, which are dramatically different for the six- and seven-coordinate structures and in excellent agreement with the measurements. V(CO)(6)(+) and Nb(CO)(6)(+) have structures slightly distorted from octahedral, while Nb(CO)(7)(+) and Ta(CO)(7)(+) have C(3v) capped octahedral structures.
通过激光汽化在分子束中产生钒族金属（V(+)、Nb(+)、Ta(+)）的气相金属羰基阳离子，然后在飞行时间光谱仪中进行质量分析和尺寸选择，并在羰基伸缩区域用红外激光光解离光谱进行研究。质谱中的丰度、碎裂模式和红外光谱提供了一种综合方法，揭示了这些体系中的配位数。尽管在每种情况下七配位结构会有18个电子，但发现形成的是V(CO)(6)(+)而不是V(CO)(7)(+)。Nb(+)形成了六配位和七配位的物种，而Ta(+)只形成了Ta(CO)(7)(+)络合物。密度泛函理论计算用于预测这些体系的红外光谱，六配位和七配位结构的红外光谱有显著差异，且与测量结果非常吻合。V(CO)(6)(+)和Nb(CO)(6)(+)的结构与八面体略有畸变，而Nb(CO)(7)(+)和Ta(CO)(7)(+)具有C(3v)帽式八面体结构。
