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Novel Types of Organic S−Fe−CO Complexes:  Reaction of [SFe3(CO)9]2- with Propargyl Bromide

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posted on 02.01.2006, 00:00 by Yun-Wen Lai, Jiann-Jang Cherng, Wen-Shyan Sheu, Gon-Ann Lee, Minghuey Shieh
We have synthesized a series of novel organic S−Fe−CO complexes from the reaction of the sulfur-capped triiron carbonyl cluster [SFe3(CO)9]2- with the bifunctional propargyl bromide and subsequent reactions. When [SFe3(CO)9]2- was treated with 2 equiv of propargyl bromide in MeCN, three new organo-bridged iron−sulfur carbonyl complexes, [Et4N][Fe3(CO)9(μ3312-CH2C(S)CHC(O))] ([Et4N][1]), (μ3-S)Fe3(CO)9(μ3121-C(H)C(CH3)) (2), and Fe2(CO)6(μ223-SC(O)C(CH3)CH) (3), were obtained. The novel anionic acyl cluster 1 is a CO insertion product and can be considered to display a SFe3 core bridged by an allylcarbonyl ligand, H2CCCHC(O), in μ231 fashion. While cluster 2 can be seen to possess a SFe3 core coordinated with a propyne ligand, CH⋮C(CH3), complex 3 exhibits a SFe2 core bridged by a α-methylvinylcarbonyl ligand, C(O)C(CH3)CH. The anionic cluster 1 could transform to 2 and 3 upon treatment with excess propargyl bromide. When [Et4N][1] was reacted with the oxidizing agent [Cu(MeCN)4][BF4], the neutral diiron complex Fe2(CO)6(μ223-C(O)CHC(S)(CH3)) (4) was obtained as the major product. Complex 4 is seen to possess a SFe2 core linked by a β-methylvinylcarbonyl ligand, C(O)CHC(CH3). More interestingly, the methylation of the acyl cluster 1 with CF3SO3Me afforded a unique triiron cluster carbene, Fe3(CO)9(μ3142-CH2C(S)CHC(OCH3)) (5). This paper describes a rare example of the reaction of a sulfur-capped triiron cluster with the bifunctional propargyl bromide and related reactions, in which a new series of iron−sulfur carbonyl complexes coordinated with novel organic fragments results, and the relative stability of some resultant complexes is discussed on the basis of theoretical calculations.

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