Reactions of an antimony containing cage compound with metal carbonyls:: synthesis and structural characterization of [{M(CO)5}2(η1:η1-P4Sb2C4But4)], M = Cr, Mo or W, and [{Fe(CO)4}2{Fe(CO)3(η3:η1-P4Sb2C4But4)}]

The antimony containing cage compound, P4Sb2C4Bu4t, was treated with an excess of [M(CO)(5)(THF)], M=Cr, Mo or W, to produce the 2:1 adduct complexes, [{M(CO)(5)}(2)(eta(1):eta(1)- P4Sb2C4Bu4t)], which X-ray crystallographic studies have shown to contain one M(CO)(5) fragment co-ordinated to an unsaturated phosphorus centre and one co-ordinated to an antimony centre. In contrast, its reaction with an excess of [Fe-2(CO)(9)] produced [{Fe(CO)(4)}(2){Fe(CO)(3)(eta(3):eta(1)-P4Sb2C4Bu4t)}], which is probably formed by the insertion of an Fe(CO)(3) fragment into an Sb-P bond of the cage. Its crystal structure confirms that it contains two eta(1)-co-ordinated Fe(CO)(4) groups and a 1,3-diphosphaallyl fragment eta(3) co-ordinated to an Fe(CO)(3) moiety.