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)}]

Abstract

The antimony containing cage compound, P₄Sb₂C₄Bu^t₄, 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-P₄Sb₂C₄Bu^t₄)], 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(η³∶η¹-P₄Sb₂C₄Bu^t₄)}], 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.