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• 作者：Emma C. Fitzgerald ; Abdelkader Ladjarafi ; Neil J. Brown ; David Collison ; Karine Costuas ; Ruth Edge ; Jean-Franc抬ois Halet ; Fre虂de虂ric Justaud ; Paul J. Low ; Hace虁ne Meghezzi ; Thierry Roisnel ; Mark W. Whiteley ; Claude Lapinte
• 刊名：Organometallics
• 出版年：2011
• 出版时间：August 8, 2011
• 年：2011
• 卷：30
• 期：15
• 页码：4180-4195
• 全文大小：1231K
• 年卷期：v.30,no.15(August 8, 2011)
• ISSN：1520-6041

文摘

Reaction of [FeCl(dppe)Cp*] with [Mo(C鈮C₆H₄-4-C鈮H)(dppe)(畏-C₇H₇)], 1, and NaBPh₄ in methanol gives the alkynylvinylidene complex [{Fe(dppe)Cp*}{渭-C鈮C₆H₄(H)C鈺怌}{Mo(dppe)(畏-C₇H₇)}]BPh₄, [2A]BPh₄, which is deprotonated to form the heterobimetallic, 1,4-diethynylbenzene-bridged complex [{Fe(dppe)Cp*}(渭-C鈮C₆H₄C鈮){Mo(dppe)(畏-C₇H₇)}], 3. The alkynylvinylidene compound [2A]BPh₄ exists as the major component of an equilibrium mixture with [Fe(dppe)Cp*}{渭-C鈺怌(H)C₆H₄C鈮}{Mo(dppe)(畏-C₇H₇)}]BPh₄, [2B]BPh₄, and is formed as a consequence of proton migration between the C_尾 carbons of the vinylidene and alkynyl ends of the bridging ligand. Cyclic voltammetric investigations reveal that 3 undergoes two reversible one-electron oxidations to cationic [3]⁺ and [3]²⁺, which have been isolated as the [PF₆]^{鈭?/sup> salts after chemical oxidation. Computational (DFT) studies on [3]n+ indicate that while the HOMO of neutral 3 is rather heavily localized on the Mo center, in [3]+ the frontier orbitals are more evenly distributed over both metals, with the concentration of spin density being sensitive to the relative disposition of the metal end-cap fragments about the diethynylbenzene ligand. Experimental investigations on [3]PF₆ by IR and EPR spectroscopy provide evidence for the coexistence of redox isomers [3A]+ and [3B]+, in which spin density is localized at the molybdenum or iron center, respectively. The solution IR spectrum of [3]PF₆ exhibits an unusual four-band pattern in the 谓(C鈮) region, consistent with the observation of two isomeric forms of [3]PF₆, which are 鈥渧alence trapped鈥?on the short time scale of IR spectroscopy. In the frozen solution EPR spectrum, at 120 K, the spectroscopic signatures of both paramagnetic end-caps Mo(dppe)(畏-C₇H₇) and Fe(dppe)Cp* are observed. The properties of [3]n+ are discussed with reference to the parent homobimetallics [{ML_x}₂(渭-C鈮C₆H₄C鈮)]n+ [ML_x = Fe(dppe)Cp*, [4]n+, and Mo(dppe)(畏-C₇H₇), [5]n+, n = 0, 1, 2].}