Preparation and properties of the halogenoalkyl compounds [(η5-C5H5)(CO)2(PPhiMe3−i)Mo{(CH2)nX}] (n=3, 4; i=0–3; X=Br, I) and [{η5-C5(CH3)5}(CO)3Mo{(CH2)nX}] (n=3, 4; X=Br, I) and the crystal structures of [(η5-C5H5)(CO)3W{(CH2)5I}], [(η5-C5H5)(CO)3W{(CH2

The compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nBr}] (Cp=η5-C5H5, n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nBr}] (Cp*=η5-C5(CH3)5, n=3, 4) were prepared in medium to high yield by the reaction of the corresponding anion ([Cp(CO)2(PPhiMe3−i)Mo]− or [Cp*(CO)3Mo]−) with Br(CH2)nBr. The bromoalkyl compounds were subsequently reacted with NaI to give the corresponding iodoalkyl compounds [Cp(CO)2(PPhiMe3−i)Mo{(CH2)nI}] (n=3, 4; i=0–3) and [Cp*(CO)3Mo{(CH2)nI}] (n=3, 4). The iodoalkyl compounds can also be prepared by the reaction of the corresponding anion and α,ω-diiodoalkane in much lower yields. These compounds have been fully characterised and their properties are discussed. The crystal and molecular structure of [Cp(CO)2(PPh3)Mo{(CH2)3I}] is reported. The compound forms crystals in the monoclinic space group P21/n, with a Mo–C bond length of 2.40 Å and a C–I bond length of 2.13 Å. The compounds [Cp(CO)3W{(CH2)nX}] (X=Br, I; n=3–6) were also prepared in high yield and the crystal structures of [Cp(CO)3W{(CH2)5I}] and [Cp(CO)3W{(CH2)3Br}] are reported. The former compound forms orthorhombic crystals in the space group P21nb and the latter forms triclinic crystals in the space group . Both have W–C bond lengths of 2.35 Å. The C–I bond length is 2.12 Å; the C–Br bond length is 1.94 Å.