Insertion reactions of hexafluorobut-2-yne, tetrafluoroethylene, and hexafluoroacetone with η5-cyclopentadienyl-iron, -ruthenium, -palladium, and -molybdenum complexes; molecular and crystal structures of [Fe2(CO){C4(CF3)4CO}(η5-C5H5)2] and [Fe{COCF2C5H5}(η5-C5H5)

Abstract

Reaction (u.v. irradiation) of [{Fe(CO)2(η5-C5H5)}2] with hexafluorobut-2-yne (hfb) gives [Fe2(CO){C8F12CO}(η5-C5H5)2], structurally identified by X-ray crystallography as a ferracyclohexadienone complex. The ruthenium compound [{Ru(CO)2(η5-C5H5)}2] reacts with hfb to give [Ru{trans-C(CF3):C(CF3)H}(CO)2(η5-C5H5)], which subsequently affords the bis-insertion product [[graphic omitted](CF3)H}(CO)(η5-C5H5)]. Irradiation of [FeMe(CO)2(η5-C5H5)] and hfb affords [[graphic omited]Me(η5-C5H5)], which exists in solution as two interconverting conformers. Treatment of [MnMe(CO)5] with hfb gives the insertion product [Mn{cis-C(CF3):C(CF3)Me}(CO)5]. Reaction of [Fe(η1-C3H5)(CO)2(η5-C5H5)] with hfb gives only the cis mono-insertion product, whereas, the corresponding molybdenum system [Mo(η1-C3H5)(CO)3(η5-C5H5)]affords a bis-insertion product; the first step probably involves a trans-insertion. A second product is [Mo2(CO)4(CF3C2CF3)(η5-C5H5)2]. The photolytic reaction of [Pd(η3-C3H5)(η5-C5H5)] and hfb, in contrast with the Fe and MO systems, gives a dinuclear complex [Pd2C4(CF3)4(η3-C3H5)(η5-C5H5)]. Irradiation of hfb and [Fe(η1-C5H5)(CO)2(η5-C5H5)] gives a product corresponding to a formal (2 + 4)π addition to an unco-ordinated substituted cyclopentadiene, followed by a carbonyl insertion reaction. Tetrafluoroethylene undergoes an unusual carbon–carbon double bond cleavage on reaction with [Fe(η1-C5H5)(CO)2(η5-C5H5)] to give [Fe(COCF2C5H5)(η5-C5H5)], structurally characterised by X-ray crystallography. Hexafluoroacetone (hfa) readily reacts at low temperature with [Fe(η1-C5H5)(CO)2(η5-C5H5)] to give products, in which the hfa has formally inserted into a C–H bond on the σ-bonded C5 ring.