| Abstract
| - The reactions of[Et4N]3[Sb{Fe(CO)4}4]with RX (R = Me, Et, n-Pr; X = I) in MeCN form themonoalkylated antimony complexes[Et4N]2[RSb{Fe(CO)4}3]and the dialkylated antimony clusters[Et4N][R2Sb{Fe(CO)4}2],respectively. The mixed dialkylantimony complex[Et4N][MeEtSb{Fe(CO)4}2]also can be synthesized from the reaction of[Et4N]2[MeSb{Fe(CO)4}3]with EtI. While the reaction withBr(CH2)2Br produces[Et4N]2[BrSb{Fe(CO)4}3],the treatment with Cl(CH2)3Br formsthe monoalkylated product[Et4N][Cl(CH2)3Sb{Fe(CO)4}3]and a novel dialkylated antimony−iron complex[Et4N][{μ-(CH2)3}Sb{Fe(CO)4}3].On the other hand, the reaction withBr(CH2)4Br forms the monoalkylatedantimony product and the dialkylated antimony complex[Et4N][{μ-(CH2)4}Sb{Fe(CO)4}2].The reactions with alkyl halides and dihalides basically proceedthrough a two-step alkylation mechanism and provide facile methodologyfor the synthesis of a series of alkylantimony ironclusters.
- The reactions of[Et4N]3[Sb{Fe(CO)4}4](1) with RX (R = Me, Et, n-Pr; X = I) in MeCNform the monoalkylatedantimony complexes[Et4N]2[RSb{Fe(CO)4}3](R = Me, 2; R = Et, 4; R = n-Pr,6) and the dialkylated antimonyclusters[Et4N][R2Sb{Fe(CO)4}2](R = Me, 3; R = Et, 5; R = n-Pr,7), respectively. When[Et4N]3[Sb{Fe(CO)4}4] reacts with i-PrI, onlythe monoalkylated antimony complex[Et4N]2[i-PrSb{Fe(CO)4}3](8) is obtained.The mixed dialkylantimony complex[Et4N][MeEtSb{Fe(CO)4}2](9) also can be synthesized from the reactionof 2 with EtI. While the reaction withBr(CH2)2Br produces[Et4N]2[BrSb{Fe(CO)4}3](10), treatment with Cl(CH2)3Br forms the monoalkylated product[Et4N]2[Cl(CH2)3Sb{Fe(CO)4}3](11) and a dialkylated novel antimony−iron complex[Et4N][{μ-(CH2)3}Sb{Fe(CO)4}3](12). On the other hand, the reaction withBr(CH2)4Br forms themonoalkylated antimony product and the dialkylated antimony complex[Et4N][{μ-(CH2)4}Sb{Fe(CO)4}2](13).Complexes 2−13 are characterized byspectroscopic methods or/and X-ray analyses. On the basis of theseanalyses,the core of the monoalkyl clusters consists of a central antimony atomtetrahedrally bonded to one alkyl groupand three Fe(CO)4 fragments and the dialkyl productsare structurally similar to the monoalkyl clusters, withthecentral antimony bonded to two alkyl groups and twoFe(CO)4 moieties in each case. The dialkylcomplex 3crystallizes in the monoclinic space group P21/c witha = 13.014(8) Å, b = 11.527(8) Å,c = 17.085(5) Å, β =105.04(3)°, V = 2475(2) Å3, andZ = 4. Crystals of 12 are orthorhombic, ofspace group Pbca, with a =14.791(4) Å, b = 15.555(4) Å, c =27.118(8) Å, V = 6239(3) Å3, andZ = 8. The anion of cluster 12 exhibits acentralantimony atom bonded to three Fe(CO)4 fragments with a−(CH2)3− group bridging between the Sb atomandone Fe(CO)4 fragment. This paper discusses thedetails of the reactions of[Et4N]3[Sb{Fe(CO)4}4]with a seriesof alkyl halides and dihalides. These reactions basically proceedvia a novel double-alkylation pathway, and thisfacile methodology can as well provide a convenient route to a seriesof alkylated antimony−iron carbonyl clusters.
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