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(μ3-η3:η1: η2-CH2C(S)CHC(O))] ([Et4N]-), (μ3-S)Fe3(CO)9(μ3- η1:η2:η1-C(H)=C(CH3)) (2), and Fe2(CO)6(μ2-η1: η2:η1-C(H)=C(CH3CH)) (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 μ2-η3:η1 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] was reacted with the oxidizing agent [Cu(MeCN)4][BF4], the neutral diiron complex Fe2(CO)6(μ2- η2:η3-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 CF3SO 3Me afforded a unique triiron cluster carbene, Fe3(CO) 9(μ3-η1:η4: η2-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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