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Carbonylchromium Monotelluride Complexes [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3):  Two Important Intermediates

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posted on 24.11.2003, 00:00 by Minghuey Shieh, Li-Fang Ho, Yu-Wen Guo, Shu-Fen Lin, Yi-Chun Lin, Shie-Ming Peng, Yi-Hung Liu
The first isolation of the monotelluride-bridged chromium carbonyl complexes [Et4N]2[Te{Cr(CO)5}n] (n = 3, [Et4N]2[1]; n = 2, [Et4N]2[2]) has been achieved from the reaction of Te powder with 3 equiv of Cr(CO)6 in the presence of [Et4N]Br in concentrated KOH/EtOH solution. According to X-ray analysis, anion 1 displays a pyramidal geometry with the Te atom bonded to three Cr(CO)5 fragments and anion 2 exhibits a nonlinear structure with the Te atom coordinated with two Cr(CO)5 moieties. Complex 1 can transform to 2 in the presence of Cr(CO)6/KOH/EtOH solution. Conversely, 2 can convert back to 1 upon the reaction with Cr(CO)6 in MeCN. Interestingly, the novel C−O activation of MeOH is observed when 1 was treated with NaOH/MeOH solution at 70 °C, giving the Te-methylated product [Et4N][MeTe{Cr(CO)5}2] ([Et4N][3]). Complex 2 is reactive toward some organic solvents. It can react with CH2Cl2 to form the CH2-bridged tetrachromium complex [Et4N]2[CH2{TeCr2(CO)10}2] ([Et4N]2[4]) and can transform to the known tetrachromium tritelluride complex [Et4N]2[Te3{Cr(CO)5}4], in MeOH solution. Besides, we also found that 2 can undergo oxidative coupling with [Cu(MeCN)4]BF4 in MeOH to form the dimeric open cluster [Te2{Cr(CO)5}4]2- and can react with NaOH in MeOH to give the dimeric ring complex [Te2Cr4(CO)18]2-. Complexes 14 are fully characterized by spectroscopic methods and single-crystal X-ray analysis. This paper describes that complexes 1 and 2 are important intermediates for a series of tellurium-containing polychromium complexes, and the interesting structural features of the resultant new polychromium carbonyl complexes are compared as well.

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