Diiron Carbonyl Complexes Bearing an N,C,S-Pincer Ligand: Reactivity toward Phosphines, Heterolytic Fe-Fe Cleavage, and Electrocatalytic Proton Reduction

作者：Hirotsu Masakazu^*; Santo Kiyokazu; Tsuboi Chiaki; Kinoshita Isamu

来源：Organometallics, 2014, 33(16): 4260-4268.

DOI：10.1021/om500558h

The thiolate-bridged diiron carbonyl complex [{Fe(mu-PyBPT-kappa N-3,C,S)(CO)(2)}Fe(CO)(3)] (1) consists of two units, Fe(PyBPT)(CO)(2) and Fe(CO)(3), where the N,C,S-pincer ligand PyBPT is a doubly deprotonated form of 3%26apos;-(2 %26apos;%26apos;-pyridyl)-1,1%26apos;-biphenyl-2-thiol. The two Fe complex units are connected through a thiolate S atom, it coordination, and an Fe Fe bond. Diiron complex 1 reacted with 1 equiv of dimethylphenylphosphine to form the CO substitution product [{Fe(mu-PyBPT-kappa N-3,C,S)(CO)(2)}Fe(CO)(2)(PMe2Ph)] (3) via the phosphine adduct [{Fe(mu-PyBPT-kappa N-3,C,S)(CO)(2)}Fe(CO)(3)(PMe2Ph)] (2), which has a polarized Fe Fe bond. A further reaction of 3 with PMe2Ph produced the N,C,S-pincer iron(II) complex trans-[Fe(PyBPT-kappa N-3,C,S)(CO)(PMe2Ph)(2)] (4) and the iron(0) complex trans-[Fe(CO)(3)(PMe2Ph)(2)]. 1,2-Bis(diphenylphosphino)benzene (dppbz) abstracted the Fe(CO)(3) unit from 1 to give the dimeric diiron(II,II) complex RFe(mu-PyBPT-kappa N-3,C,S)(CO)(2)}(2)] (7) and the iron(0) complex [Fe(CO)(3)(dppbz)]. The asymmetric bridging ligand PyBPT and coordination of the phosphines induce polarization of the Fe Fe bond, which leads to the formation of the iron(II) and iron(0) complexes via heterolytic Fe Fe cleavage. Electrochemical properties of 3 and 4 were investigated by cyclic voltammetry. Complex 3 showed two one-electron-reduction processes, the potentials of which are ca. 0.4 V more negative than those of 1. Electrocatalytic proton reduction by 3 was investigated, and the efficiency was comparable to that of 1.

• 出版日期2014-8-25