REACTIONS OF [ET(4)N](3)[SB(FE(CO)(4))(4)] WITH ALKYL-HALIDES AND DIHALIDES - FORMATION OF THE ALKYLANTIMONY 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(C0)(4)}(2)] (R = Me, 3; R = Et, 5; R = n-Pr, 7), respectively. When [Et(4)N](3)[Sb{Fe(C0)(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 dialkylantimo ny 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(CH2)(2)Br produces [Et(4)N](2)[BrSb{Fe(C0)(4)}(3)] (10), treatment with Cl(CH2)( 3)Br forms the monoalkylated product [Et(4)N](2)[Cl(CH2)(3)Sb{Fe(C0)(4 )}(3)] (11) and a dialkylated novel antimony-iron complex [Et(4)N][{mu -(CH2)(3)}Sb{Fe(C0)(4)}(3)] (12). On the other hand, the reaction with Br(CH2)(4)Br forms the monoalkylated antimony product and the dialkyl ated antimony complex [Et(4)N][{mu-(CH2)(4)}Sb{Fe(CO)(4)}(2)] (13). Co mplexes 2-13 are characterized by spectroscopic methods or/and X-ray a nalyses. On the basis of these analyses, the core of the monoalkyl clu sters consists of a central antimony atom tetrahedrally bonded to one alkyl group and three Fe(C0)4 fragments and the dialkyl products are s tructurally similar to the monoalkyl clusters, with the central antimo ny bonded to two alkyl, groups and two Fe(C0)(4) moieties in each case . The dialkyl complex 3 crystallizes in the monoclinic space group P2( l)/c with a = 13.014(8) Angstrom, b = 11.527(8) Angstrom, c = 17.085(5 ) Angstrom, beta = 105.04(3)degrees, V = 2475(2) Angstrom(3), and Z = 4. Crystals of 12 are orthorhombic, of space group Pbca, with a = 14.7 91(4) Angstrom, b = 15.555(4) Angstrom, c = 27.118(8) Angstrom, V = 62 39(3) Angstrom(3), and Z = 8. The anion of cluster 12 exhibits a centr al antimony atom bonded to three Fe(CO)(4) fragments with a -(CH2)(3)- group bridging between the Sb atom and one Fe(C0)(4) fragment. This p aper discusses the details of the reactions of [Et(4)N](3)[Sb{Fe(C0)(4 )}(4)] with a series of alkyl halides and dihalides. These reactions b asically proceed via a novel double-alkylation pathway, and this facil e methodology can as well provide a convenient route to a series of al kylated antimony-iron carbonyl clusters.