Organometallic chemistry of fluorinated allenes

Reaction of 1,1-difluoroallene and tetrafluoroallene with a series of transition metal complex fragments yields the mononuclear allene complexes [CpMn(CO)(2)(allene)] (1), [(CO)(4)Fe(allene)] (2), [(Ph(3)P)(2)Pt(C(3)H(2)F(2))] (4), [Ir(PPh(3))(2)(C(3)H(2)F(2))(2)Cl] (5), and the dinuclear complexes [mu-eta(1)-eta(3)-C(3)H(2)F(2))Fe(2)(CO)(7)] (3), [Ir(PPh(3))(C(3)H(2)F(2))(2)Cl](2) (6), and [mu-eta(2)-eta(2)-C(3)H(2)F(2))(CpMo(CO)(2))(2)] (9), respectively. In attempts to synthesize cationic complexes of fluorinated allenes [CpFe(CO)(2)(C(CF(3))=CH(2))] (7a), [CpFe(CO)(2)(C(CF(3))=CF(2))] (7b) and [mu-I-(CpFe(CO)(2))(2)][B(C(6)H(3)-3,5-(CF(3))(2))(4)] were isolated. The spectroscopic and structural data of these complexes revealed that the 1,1-difluoroallene ligand is coordinated exclusively with the double bond containing the hydrogen-substituted carbon atom. 1,1-Difluoroallene and tetrafluoroallene proved to be powerful pi acceptor ligands.