Reactions of Iron Acyl Chalcogenide Clusters with Electrophiles: Reactivity Comparison and Theoretical Calculations

摘要

The reactions of two types of EFe_3-based acyl clusters [EFe_3(CO)_9C(O)C(H)CCH_2)]~- (E = S, 1; Se, 2; Te, 3) with different electrophiles have been systematically studied and compared. When the sulfur-substituted allylcarbonyl Fe_3-cluster [Fe_3(CO)_9{μ_3-η~2:η~1:η~3-C(O)CHC(S)CH_2}]~- (1) was treated with CH_3COCl in CH_2Cl_2, the Fischer-type acyloxy carbene cluster [Fe_3(CO)_9{μ_3-η~2:η~4:η~1-C(OCOCH_3)-C(H)C(S)CH_2}] (4) was obtained, along with the previously reported SC(O)C(CH_3)=CH bridged Fe_2-complex [Fe_2(CO)_6{μ-η~2:η~3-SC(O)C(CH_3)CH}] (5) and [HSFe_3(CO)_9]~-. Similar acetylation of the allylcarbonyl SeFe_3-cluster [(μ_3-Se)Fe_3(CO)_9(μ_3-η~1:η~1:η~3- C(O)C(H)CCH_2)]~- (2) produced the Fe_2-carbene complex [Fe_2(CO)_6{μ-η~2:η~3-C(OCOCH_3)C(H)C(Se)CH_2}] (6) and the propyne-bridged SeFe_3-complex [(μ_3-Se)Fe_3(CO)_9{(μ_3-η~1:η~2:η~1-C(CH_3)=C(H)}] (7) as well as [HSeFe_3(CO)_9]~- and [Se_2Fe_3(CO)_9]. However, when the analogous TeFe_3-based allylcarbonyl cluster [((μ_3-Te)Fe_3(CO)_9(μ_3-η~1:η~1:η~3-C(O)C(H)CCH_2)]~- (3) reacted with CH_3COCl, only the fragmentation product [Te_2Fe_3(CO)_9] was formed. Further acidification of cluster 1 with HBF_4 proceeded to form complex 5 and [HSFe_3(CO)_9]~-. Similar acidification of 2 formed the propyne-capped complex 7, however, the protonation of 3 led to the formation of [Te_2Fe_3(CO)_9]. Contrast to the reported reactions of 1 and 3, the reaction of 2 with [Cu(CH_3CN)_4][BF_4] formed complex 7 and a new C(O)CH=C(Se)(CH_3) bridged Fe_2-complex [Fe_2(CO)_6{μ-η~2:η~3-C(O)CHC(SeXCH_3)}] (8). The nature and formation of new carbene complexes 4 and 6 were further elucidated with the aid of molecular orbital calculations at the B3PW91 level of density functional theory.