Reaction of the tellurium-capped triiron cluster [TeFe₃(CO) ₉]^2- with the bifunctional propargyl bromide: Formation of a series of novel organic Te-Fe-CO complexes

When [TeFe₃(CO)₉]^2- was treated with 1 equiv of propargyl bromide in MeCN, the novel acyl complex [Et ₄N][(μ₃-Te)Fe₃(CO) ₉(μ₃-η¹: η¹η³C(O)C(H)CCH₂)] ([Et ₄N][1]) was obtained. Cluster 1 can be viewed to consist of a TeFe₃ core which is linked by the novel allylcarbonyl ligand C(O)CHCCH₂ in a μ₃-η¹:η¹: η³ fashion. Further oxidation of cluster 1 occurs via organo ligand loss and bond rearrangement to give the oxidation product Te ₂Fe₃(CO)₉. In addition, when cluster 1 was methylated with CF₃SO₃Me, the Fischer-type carbene complex (μ³-Te)Fe₃(CO)₉(μ₃- η¹:η¹:η³-C(OMe)C(H)CCH ₂) (2) was afforded. When the ratio of reactants and reaction solvent was varied, the detailed reaction of [TeFe₃(CO)₉] ^2- with propargyl bromide could be further investigated. When [TeFe₃(CO)₉]^2- was treated with excess propargyl bromide in MeCN, the two new butterfly clusters Te₂Fe ₂(CO)₆(CH=C=CH₂)₂ (3) and Te ₂Fe₂(CO)₆(CH₂C≡CH)(CH=C= CH₂) (4) were obtained along with cluster 1. While cluster 3 displays a Te₂Fe₂ metal core with two allenyl ligands attached to the tellurium atoms in anti positions, cluster 4 consists of a Te ₂Fe₂ core with each tellurium atom coordinated to one allenyl or one propargyl ligand in an anti position. Further investigation of [TeFe₃(CO)₉]^2- with propargyl bromide in a molar ratio of 1:2 or 1:4 in CH₂Cl₂ showed that the oxidation product (μ₃-Te)Fe₃(CO) ₉(μ₃-η¹:η²: ¹-C(Me)=CH) (5) was afforded, in addition to the formation of 1, 3, and 4. Cluster 5 can be viewed to be composed of a TeFe₃ core coordinated with the propyne ligand C(Me)≡CH, which acts as a 4e donor. This paper describes the detailed reactions of [TeFe₃(CO) ₉]^2- with the bifunctional propargyl bromide in terms of the reaction solvents, the ratio of the reactants, and the chalcogen effect, and the reactivities and structural features of the resultant clusters with the novel organo moieties are systematically compared and discussed.