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Lead−Chromium Carbonyl Complexes Incorporated with Group 8 Metals: Synthesis, Reactivity, and Theoretical Calculations
journal contribution
posted on 2011-01-17, 00:00 authored by Minghuey Shieh, Yen-Yi Chu, Miao-Hsing Hsu, Wei-Ming Ke, Chien-Nan LinThe trichromium−lead complex [Pb{Cr(CO)5}3]2− (1) was isolated from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution, and the new mixed chromium−iron−lead complex [Pb{Cr(CO)5}{Fe(CO)4}2]2− (3) was synthesized from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution followed by the addition of Fe(CO)5. X-ray crystallography showed that 3 consisted of a central Pb atom bound in a trigonal-planar environment to two Fe(CO)4 and one Cr(CO)5 fragments. When complex 1 reacted with 1.5 equiv of Mn(CO)5Br, the Cr(CO)4-bridged dimeric lead−chromium carbonyl complex [Pb2Br2Cr4(CO)18]2- (4) was produced. However, a similar reaction of 3 or the isostructural triiron−lead complex [Pb{Fe(CO)4}3]2− (2) with Mn(CO)5Br in MeCN led to the formation of the Fe3Pb2-based trigonal-bipyramidal complexes [Fe3(CO)9{PbCr(CO)5}2]2− (6) and [Fe3(CO)9{PbFe(CO)4}2]2− (5), respectively. On the other hand, the Ru3Pb2-based trigonal-bipyramidal complex [Ru3(CO)9{PbCr(CO)5}2]2− (7) was obtained directly from the reaction of PbCl2, Cr(CO)6, and Ru3(CO)12 in a KOH/MeOH solution. X-ray crystallography showed that 5 and 6 each had an Fe3Pb2 trigonal-bipyramidal core geometry, with three Fe(CO)3 groups occupying the equatorial positions and two PbFe(CO)4 or PbCr(CO)5 units in the axial positions, while 7 displayed a Ru3Pb2 trigonal-bipyramidal geometry with three equatorial Ru(CO)3 groups and two axial PbCr(CO)5 units. The complexes 3−7 were characterized spectroscopically, and their nature, formation, and electrochemistry were further examined by molecular orbital calculations at the B3LYP level of density functional theory.