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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Homoleptic Tetranuclear Rhodium Carbonyls: Comparison with Their Iridium Analogues
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Homoleptic Tetranuclear Rhodium Carbonyls: Comparison with Their Iridium Analogues

机译：准四核铑羰基化合物：与铱类似物的比较

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Density functional theory confirms the experimentally known triply bridged Rh-4(CO)(9)(mu-CO)(3) structure to be the lowest-energy structure. The lowest-energy structures of the unsaturated systems Rh-4(CO)n (n = 11, 10, 9, 8) are also triply bridged structures with central Rh-4 tetrahedra that can be derived from this Rh-4(CO)(9)(mu-CO)(3) structure by removal of terminal CO groups in various ways. The M-M distances in these central M-4 tetrahedra change very little as CO groups are lost, suggesting reluctance to form metalmetal multiple bonds in these unsaturated systems. The natural bond orbital (NBO) Wiberg bond indices provide depth to this analysis. All of these unsaturated systems are predicted to be highly fluxional, as two to three isomeric structures lie within similar to 4 kcal/mol of the global minima. The Rh-4(CO)(8)(mu-CO)(2)(mu(4)-CO) structure analogous to the lowest-energy Co-4(CO)(11) structure with all four atoms of a central Co4 butterfly bridged by a mu-CO group is predicted to lie similar to 6 kcal/mol in energy above the lowest-energy Rh-4(CO)(11) structure. Comparisons of the relative energies of analogous Rh-4(CO)(n) and Ir-4(CO())n structures indicate that more highly bridged M-4(CO)(n) structures are energetically much more favorable for rhodium than for iridium. Dissociation energies (for loss of CO) and disproportionation energies are reported.
机译：密度泛函理论确认实验已知的三重桥接Rh-4（CO）（9）（mu-CO）（3）结构是最低能级结构。不饱和体系Rh-4（CO）n的最低能量结构（n = 11，10，9，8）也是具有中心Rh-4四面体的三重桥式结构，可以从该Rh-4（CO）衍生（9）（mu-CO）（3）结构，可通过各种方式除去末端CO基团。随着CO基团的丢失，这些中心M-4四面体中的M-M距离变化很小，这表明不愿意在这些不饱和体系中形成金属-金属多重键。天然债券轨道（NBO）Wiberg债券指数为这一分析提供了深度。预计所有这些不饱和系统都具有较高的通量，因为有2至3个异构体结构位于全球最小值的4 kcal / mol之内。 Rh-4（CO）（8）（mu-CO）（2）（mu（4）-CO）结构类似于具有中心一个中心的所有四个原子的最低能量Co-4（CO）（11）结构由mu-CO基桥接的Co4蝴蝶预计在最低能量Rh-4（CO）（11）结构上方的能量类似于6 kcal / mol。比较相似的Rh-4（CO）（n）和Ir-4（CO（））n结构的相对能表明，高桥联的M-4（CO）（n）结构在能量上比铑更有利于铑铱报告了离解能（用于CO的损失）和歧化能。

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