Binuclear Homoleptic Manganese Carbonyls: Mn2(CO)x (x = 10, 9, 8, 7)

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• 作者：Yaoming Xie ; Jee Hwan Jang ; R. Bruce King ; and Henry F. Schaefer ; III
• 刊名：Inorganic Chemistry
• 出版年：2003
• 出版时间：August 25, 2003
• 年：2003
• 卷：42
• 期：17
• 页码：5219 - 5230
• 全文大小：294K
• 年卷期：v.42,no.17(August 25, 2003)
• ISSN：1520-510X

文摘

The unsaturated homoleptic manganese carbonyls Mn₂(CO)_n (n = 7, 8, 9) are characterized by their equilibriumgeometries, thermochemistry, and vibrational frequencies using methods from density functional theory (DFT). Thecomputed metal-metal distances for global minima range from 3.01 Å for the unbridged Mn₂(CO)₁₀ with a Mn-Mnsingle bond to 2.14 Å for a monobridged Mn₂(CO)₇ formulated with a metal-metal quadruple bond. The globalminimum for Mn₂(CO)₉ has a four-electron bridging -²-CO group and a 2.96 Å Mn-Mn distance suggestive ofthe single bond required for 18-electron configurations for both metal atoms. This structure is closely related to anexperimentally realized structure for the isolated and structurally characterized stable phosphine complex [R₂PCH₂PR₂]₂Mn₂(CO)₄(-²-CO). An unbridged (OC)₄Mn-Mn(CO)₅ structure for Mn₂(CO)₉ has only slightly (<6 kcal/mol)higher energy with a somewhat shorter metal-metal distance of 2.77 Å. For Mn₂(CO)₈ the lowest energy structureis a D_2d unbridged structure with a 2.36 Å metal-metal distance suggesting the triple bond required for the favored18-electron configuration for both metal atoms. However, the unbridged unsymmetrical (CO)₃Mn-Mn(CO)₅ structurewith a metal-metal bond distance of 2.40 Å lies only 1 to 3 kcal/mol above this global minimum. The lowest energystructure of Mn₂(CO)₇ is an unbridged C_s structure with a short metal-metal distance of 2.26 Å. This is followedenergetically by another C_s unbridged Mn₂(CO)₇ structure with a somewhat longer metal-metal distance of 2.38 Å.