Syntheses of Pentanuclear Group 6 Iridium Clusters by Core Expansion of Tetranuclear Clusters with Ir(CO)2(畏5-C5Me4R) (R = H, Me)

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• 作者：Michael D. Randles ; Peter V. Simpson ; Vivek Gupta ; Junhong Fu ; Graeme J. Moxey ; Torsten Schwich ; Alan L. Criddle ; Simon Petrie ; Jonathan G. MacLellan ; Stuart R. Batten ; Robert Stranger ; Marie P. Cifuentes ; Mark G. Humphrey
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：October 7, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：11256-11268
• 全文大小：509K
• 年卷期：v.52,no.19(October 7, 2013)
• ISSN：1520-510X

文摘

Metal cluster core expansion at tetrahedral group 6鈥揼roup 9 mixed-metal clusters MIr₃(渭-CO)₃(CO)₈(畏⁵-L) (M = W, Mo, L = C₅H₅; M = Mo, L = C₅Me₅) with the iridium capping reagents Ir(CO)₂(畏⁵-L鈥? (L鈥?= C₅Me₅, C₅Me₄H) in refluxing toluene afforded the trigonal-bipyramidal clusters MIr₄(渭-CO)₃(CO)₇(畏⁵-C₅H₅)(畏⁵-L鈥? (M = Mo, L鈥?= C₅Me₅, 1a; M = W, L鈥?= C₅Me₅, 1b; M = Mo, L鈥?= C₅Me₄H, 1c; M = W, L鈥?= C₅Me₄H, 1d) and MoIr₄(渭₃-H)(渭-CO)₂(渭-畏¹:畏⁵-CH₂C₅Me₄)(CO)₇(畏⁵-C₅Me₅) (2). Related reactions with M₂Ir₂(渭-CO)₃(CO)₇(畏⁵-L)₂ (M = W, Mo, L = C₅H₅; M = Mo, L = C₅Me₅) afforded M₂Ir₃(渭-CO)₃(CO)₆(畏⁵-C₅H₅)₂(畏⁵-L鈥? (M = Mo, L鈥?= C₅Me₅, 3a; M = W, L鈥?= C₅Me₅, 3b; M = Mo, L鈥?= C₅Me₄H, 3c; M = W, L鈥?= C₅Me₄H, 3d), W₂Ir₃(渭-CO)₄(CO)₅(畏⁵-C₅H₅)₂(畏⁵-C₅Me₄H) (4), and Mo₂Ir₃(渭-CO)₃(CO)₆(畏⁵-C₅Me₅)₃ (5). Single-crystal X-ray diffraction studies of 1a鈥?b>1d, 2, 3a鈥?b>3d, and 4 confirmed their molecular structures, including the 渭-畏¹:畏⁵-CH₂C₅Me₄ ligand at hydrido cluster 2, derived from a C鈥揌 bond activation of one of the methyl groups. Density functional theory (DFT) studies were employed to suggest the structure of 5. The redox behavior of the new clusters was examined through cyclic voltammetry; all clusters exhibit oxidation and reduction processes (with respect to the resting state), with the oxidation processes being the more reversible, and increasingly so on decreasing Ir content of the clusters, replacing W by Mo, and increasing alkylation of the cyclopentadienyl ligands. In situ IR and UV鈥搗is鈥搉ear-IR spectroelectrochemical studies of the reversible oxidation processes in 1a and 3a were undertaken, with the spectra of the former suggesting progression to an all-terminal CO geometry concomitant with the first oxidation and a significant structural change upon the second oxidation step. DFT studies of 1a revealed that its crystallographically-confirmed Mo-equatorial core geometry is essentially isoenergetic with a possible Mo-apical isomer, and identified several bridging CO structures for the charged states.