Reactions of an antimony containing cage compound with metal carbonyls: Synthesis and structural characterization of

The antimony containing cage compound, P₄Sb₂C₄Bu₄^t, 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(η¹:η¹-P ₄Sb₂C₄Bu₄^t)], 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 [Fe₂(CO)₉] produced [{Fe(CO)₄}₂{Fe(CO)₃(η ³:η¹-P₄Sb₂C₄Bu ₄^t)}], 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 η¹-co-ordinated Fe(CO)₄ groups and a 1,3-diphosphaallyl fragment η³ co-ordinated to an Fe(CO)₃ moiety.