Allenylidene and derived alkynyl complexes of iron(II) with the {FeBr(Et2PCH2CH2PEt2)2}+ centre

The allenylidene complexes trans-[FeBr{CCC(R)Ph}(depe)2][BPh4] (depe=Et2PCH2CH2PEt2; R=Me 1, Ph 2) were obtained by treatment of a methanolic solution of trans-[FeBr2(depe)2] with the appropriate alkynol HCCC(R)Ph(OH), in the presence of Na[BPh4]. The methylallenylidene ligand in 1 undergoes reversible deprotonation (by NaOMe) to yield the enynyl (or ene–yne) complex of iron(II), trans-[FeBr{CCC(CH2)Ph}(depe)2] 3. The diphenylallenylidene ligand in 2 undergoes regioselective hydride γ-addition on reaction with K[B{CH(Me)Et}3H] to afford the alkynyl complex trans-[FeBr{CCC(H)Ph2}(depe)2] 4.