Reactions of [Et(4)N](3)[Sb{Fe(CO)(4)}(4)] with Alkyl Halides and Dihalides: Formation of the Alkyl- and the Dialkylantimony-Iron Carbonyl Complexes

The reactions of Et(4)N](3)Sb{Fe(CO)(4)}(4)] (1) with RX (R = Me, Et, n-Pr; X = I) in MeCN form the monoalkylated antimony complexes Et(4)N](2)RSb{Fe(CO)(4)}(3)] (R = Me, 2; R = Et, 4; R = n-Pr, 6) and the dialkylated antimony clusters Et(4)N]R(2)Sb{Fe(CO)(4)}(2)] (R = Me, 3; R = Et, 5; R = n-Pr, 7), respectively. When Et(4)N](3)Sb{Fe(CO)(4)}(4)] reacts with i-PrI, only the monoalkylated antimony complex Et(4)N](2)i-PrSb{Fe(CO)(4)}(3)] (8) is obtained. The mixed dialkylantimony complex Et(4)N]MeEtSb{Fe(CO)(4)}(2)] (9) also can be synthesized from the reaction of 2 with EtI. While the reaction with Br(CH(2))(2)Br produces Et(4)N](2)BrSb{Fe(CO)(4)}(3)] (10), treatment with Cl(CH(2))(3)Br forms the monoalkylated product Et(4)N](2)Cl(CH(2))(3)Sb{Fe(CO)(4)}(3)] (11) and a dialkylated novel antimony-iron complex Et(4)N]{&mgr;-(CH(2))(3)}Sb{Fe(CO)(4)}(3)] (12). On the other hand, the reaction with Br(CH(2))(4)Br forms the monoalkylated antimony product and the dialkylated antimony complex Et(4)N]{&mgr;-(CH(2))(4)}Sb{Fe(CO)(4)}(2)] (13). Complexes 2-13 are characterized by spectroscopic methods or/and X-ray analyses. On the basis of these analyses, the core of the monoalkyl clusters consists of a central antimony atom tetrahedrally bonded to one alkyl group and three Fe(CO)(4) fragments and the dialkyl products are structurally similar to the monoalkyl clusters, with the central antimony bonded to two alkyl groups and two Fe(CO)(4) moieties in each case. The dialkyl complex 3 crystallizes in the monoclinic space group P2(1)/c with a = 13.014(8) ?, b = 11.527(8) ?, c = 17.085(5) ?, beta = 105.04(3) degrees, V = 2475(2) ?(3), and Z = 4. Crystals of 12 are orthorhombic, of space group Pbca, with a = 14.791(4) ?, b = 15.555(4) ?, c = 27.118(8) ?, V = 6239(3) ?(3), and Z = 8. The anion of cluster 12 exhibits a central antimony atom bonded to three Fe(CO)(4) fragments with a -(CH(2))(3)- group bridging between the Sb atom and one Fe(CO)(4) fragment. This paper discusses the details of the reactions of Et(4)N](3)Sb{Fe(CO)(4)}(4)] with a series of alkyl halides and dihalides. These reactions basically proceed via a novel double-alkylation pathway, and this facile methodology can as well provide a convenient route to a series of alkylated antimony-iron carbonyl clusters.