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

The first isolation of the monotelluride-bridged chromium carbonyl complexes [Et 4 N] 2 [Te-{Cr(CO) 5 } n ] (n = 3, [Et 4 N] 2 [1]; n = 2, [Et 4 N] 2 [2]) has been achieved from the reaction of Te powder with 3 equiv of Cr(CO) 6 in the presence of [Et 4 N]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 ] ([Et 4 N][3]). Complex 2 is reactive toward some organic solvents. It can react with CH 2 Cl 2 to form the CH 2 -bridged tetrachromium complex [Et 4 N] 2 [CH 2 {TeCr 2 -(CO) 1 0 } 2 ] ([Et 4 N] 2 [4]) and can transform to the known tetrachromium tritelluride complex [Et4N] 2 [Te 3 {Cr(CO) 5 } 4 ], in MeOH solution. Besides, we also found that 2 can undergo oxidative coupling with [Cu(MeCN) 4 ]BF 4 in MeOH to form the dimeric open cluster [Te 2 {Cr(CO) 5 } 4 ] 2 - and can react with NaOH in MeOH to give the dimeric ring complex [Te 2 Cr 4 (CO) 1 8 ] 2 - . Complexes 1-4 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.