REACTIVITY OF IRON(II) NONCLASSICAL HYDRIDES WITH ALKYNES

The complex [FeH(eta2-H2){PPh(OEt)2}4]BPh4 reacts with terminal alkynes HC=CR (R = p-tolyl, Bu(t) or SiMe3) to give the corresponding alkenes H2C=CHR and the butenynyl derivative [Fe(eta3-RC3CHR){PPh(OEt)2}4]+. In contrast, the related complex [FeH(eta2-H2){P(OEt)3}4]BPh4 reacts with terminal alkynes to yield alkenes and sigma-acetylide [Fe(C=CR){P(OEt)3}5]+ derivatives. Activated alkynes such as HC=CCO2Me and MeO2CC=CCO2Me react with both [FeH(eta2-H2)L4]BPh4 [L = P(OEt)3 or PPh(OEt)2] to give vinyl derivatives [Fe{CH=CH(CO2Me)}L4]+ and [Fe{C(CO2Me)=CH(CO2Me)}L4]+, respectively. The characterization of the complexes by IR, H-1, C-13 and P-31 NMR spectroscopy is discussed.