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• 作者：Hannah N. Roberts ; Neil J. Brown ; Ruth Edge ; Emma C. Fitzgerald ; Yien T. Ta ; David Collison ; Paul J. Low ; Mark W. Whiteley
• 刊名：Organometallics
• 出版年：2012
• 出版时间：September 10, 2012
• 年：2012
• 卷：31
• 期：17
• 页码：6322-6335
• 全文大小：528K
• 年卷期：v.31,no.17(September 10, 2012)
• ISSN：1520-6041

文摘

Two series of extended carbon chain butadiynyl and hexatriynyl complexes, [Mo{(C鈮)_nC鈮SiMe₃}(bpy)(畏-C₇H₇)] (n = 1, 2; bpy = 2,2鈥?bipyridine) and [Mo{(C鈮)_nC鈮R}(dppe)(畏-C₇H₇)] (n = 1, R = H, SiMe₃; n = 2, R = SiMe₃; dppe = Ph₂PCH₂CH₂PPh₂), have been prepared and structurally characterized. The redox chemistry of these complexes has been investigated by cyclic voltammetry, and the 17-electron radical cations resulting from one-electron oxidation have been characterized by spectroelectrochemical IR and UV鈥搗isible methods and EPR spectroscopy. DFT calculations on the H-terminated model complexes [Mo{(C鈮)_nC鈮H}(L₂)(畏-C₇H₇)]^z+ (L₂ = bpy, dppe) reveal a largely metal-centered HOMO (z = 0) with a modest increase in carbon chain character with increasing chain length. Spin density calculations for the 17-electron radical cations (z = 1) show large coefficients of spin density at the metal center, consistent with the remarkably high stability of the experimental complexes. However, both DFT theoretical and experimental synthetic studies highlight a distinction between the bpy- and dppe-supported systems. The 17-electron complexes [Mo{(C鈮)_nC鈮SiMe₃}(bpy)(畏-C₇H₇)]PF₆ (n = 1, 2) are unique examples of isolable, metal-stabilized butadiynyl and hexatriynyl radicals. In contrast, the dppe radical [Mo(C鈮C鈮SiMe₃)(dppe)(畏-C₇H₇)]⁺ exhibits chain-centered reactivity, consistent with enhanced coefficients of spin density at C_尾 and C_未 in the model complex [Mo(C鈮C鈮H)(dppe)(畏-C₇H₇)]⁺.