Reaction of [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3) toward Electrophiles: Reactivity Comparison and Theoretical Calculations

Abstract

Reactions of [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3) with a series of organic and inorganic electrophiles have been systematically studied and compared. When [Et4N]2[Te{Cr(CO)5}2] was protonated with ∼1.0 equiv of HBF4 in MeCN, the monohydrido Te−Cr complex [Et4N][HTe{Cr(CO)5}2] ([Et4N][1]) was obtained. However, similar protonation of [Et4N]2[Te{Cr(CO)5}3] led to the formation of the decomposition product [Et4N]2[Te2{Cr(CO)5}4]. While methylation of [Et4N]2[Te{Cr(CO)5}2] with CF3SO3Me formed mono- and dimethylated products [Et4N][MeTe{Cr(CO)5}2] and Me2Te{Cr(CO)5}2 (2) stepwise, a similar reaction with [Et4N]2[Te{Cr(CO)5}3] produced the monomethylated product [Et4N][MeTe{Cr(CO)5}3] (3). Further, when [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3) was stirred in CH2Cl2 at 0 °C, the Cl-functionalized products [Et4N][ClH2CTe{Cr(CO)5}n] (n = 2, [Et4N][4]; n = 3, [Et4N][5]) were produced, respectively. Similar reactions with CH2Cl2 at room temperature produced corresponding CH2-bridged dimeric products [Et4N]2[CH2Te2{Cr(CO)5}n] (n = 4; 6, [Et4N]2[6]). If the bisbenzyl-containing reagent ClH2C(C6H4)2CH2Cl reacted with [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3), the corresponding CH2(C6H4)2CH2-bridged dimeric complexes [Et4N]2[H2C(C6H4)2CH2Te2{Cr(CO)5}n] (n = 4, [Et4N]2[7]; n = 6, [Et4N]2[8]) were produced. [Et4N]2[Te{Cr(CO)5}n] (n = 2, 3) could further react with HgCl2 in THF to give corresponding Hg-bridged products [Et4N]2[HgTe2{Cr(CO)5}n] (n = 4, [Et4N]2[9]; n = 6, [Et4N]2[10]). Complex 9 was found to transform to complex 10 upon its reaction with HgCl2 in THF. Interestingly, the novel O2-activation product [Et4N][OTe{Cr(CO)5}2] ([Et4N][11]) was observed when [Et4N]2[Te{Cr(CO)5}2] was bubbled with O2 in MeCN. Complexes 1−11 were fully characterized by elemental analysis, spectroscopic methods, and/or single-crystal X-ray analysis. The nature of [Te{Cr(CO)5}n]2- (n = 2, 3) and the resultant complexes were further investigated by molecular orbital calculations at the B3LYP level of the density functional theory.