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Synthesis, Characterization, and Reactivity of the Heterometallic Dinuclear μ-PH2 and μ-PPhH Complexes FeMn(CO)8(μ-PH2) and FeMn(CO)8(μ-PPhH)

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journal contribution
posted on 25.10.2010, 00:00 authored by Adam C. Colson, Kenton H. Whitmire
Deprotonation of Fe(CO)4PRH2 and treatment with Mn(CO)5Br afforded the dinuclear complexes FeMn(CO)8(μ-PRH) (1a, R = H; 1b, R = Ph), which contain the relatively rare μ-PH2 and μ-PPhH functionalities. The heterometallic nature of these complexes was confirmed by mass spectrometry, and the molecular structures of 1a and 1b were determined by X-ray diffraction experiments. Deprotonation of 1b and subsequent addition of Mn(CO)5Br or AuPPh3Cl yielded the trinuclear complexes FeMn(CO)8[μ-PPh(Mn(CO)5)] (3a) and FeMn(CO)8[μ-PPh(AuPPh3)] (3b), both of which were characterized structurally and spectroscopically. Deprotonation of 1a at room temperature resulted in rapid coupling of the deprotonated product [2a] with neutral 1a to form M+[FeMn(CO)83-PH)Mn(CO)4(μ-PH2)Fe(CO)4] (M+[4]) (M+ = Li+, Na+, K+), the formation of which was observed using in situ infrared spectroscopy. M+[4] was found to decompose upon solvent removal, and the structure of [4] was elucidated by examination of spectroscopic data. The 1H NMR spectrum of [4]- was characterized by first-order [ABMX] and [AMX] spin systems, and ESI-MS data confirmed that [4] was formed by direct coupling of [2a] with 1a without concomitant fragmentation or loss of CO ligands. Deprotonation of 1a at lower temperatures slowed the coupling process, allowing for the metalation of the monomeric anion [2a] by treatment with AuPPh3Cl, the product of which was found to decompose gradually in solution and rapidly upon concentration.