Metal fragment condensation and carbon–carbon bond cleavage in reactions of [Fe3(CO)12] with internal propargyl alcohols. Structures of the “bow tie” acetylide complexes [Fe5(CO)14(C2R)2] (R =Me or Et)

Abstract

The propargyl alcohols RC 2 C(H)(OH)RЈ (R = H, RЈ = Et; R = Me, RЈ = Et; R = Et, RЈ = Me; R = Ph, RЈ = Pr i ) reacted with [Fe 3 (CO) 12 ] in hydrocarbon solvents to give, as the final products, binuclear "ferrole" derivativesalcohol] in several isomers. Small amounts of tri-and penta-nuclear complexes were also obtained. In particular, when R = H or Ph trinuclear complexes [Fe 3 (CO) 9 -(µ-CO)L] 1 with a "parallel" alkyne ligand could be isolated and characterized by IR and NMR spectroscopies and mass spectrometry. When R = Me or Et the "bow tie" acetylide complexes [Fe 5 (CO) 14 (C 2 R) 2 ] (R = Me 2a or Et 2b) were isolated; their structures were determined by X-ray diffraction. The complexes 2a and 2b are formed by two Fe 3 triangles sharing a common vertex: each triangle is co-ordinated in a perpendicular fashion by an acetylide fragment and the carbon of one of the acetylide ligands is bound to four iron atoms. Complexes 2 are new examples of an uncommon type of cluster framework; they are presumably formed upon condensation of metal fragments generated by triiron dodecacarbonyl and upon cleavage of a carbon-carbon bond α to the alkyne triple bond. Possible formation mechanisms are discussed.

Activation of propargylic alcohols by dimolybdenum tris(μ-thiolate) complexes: Influence of the substituents R in HCCCR2(OH)-vinylidene/allenylidene transformation. Reactivity of allenylidene complexes

“…Elimination of acetone involves a highly reactive hydroxyvinylidene complex 5, which simultaneously undergoes a C b -C c bond cleavage and an internal proton addition to the nucleophilic C b atom of the unsaturated chain. Elimination of a ketone in this way is rare, and we know of only one similar example which involves the reaction of Fe 3 (CO) 12 with internal propargylic alcohols to give uncharacterised products [6]. Interestingly, the reaction observed here is the reverse of the synthetic route to propargylic alcohols based on the condensation of an alkyne with a ketone [22].…”

“…A brick-red solid readily precipitated from the solution and was collected by filtration and washed with diethyl ether (3 · 15 mL). The 1 H NMR spectrum of the resultant powder (129 mg) indicated the presence mainly of six products 5,6,7,9,10 and 8, in a molar ratio of 9.5:1.25:1:1:1 and 0.25. Attempts to separate cleanly the complexes by either chromatography or crystallisation failed, and therefore no analytical data are available for the main new products 5 and 7.…”

“…The precise factors which govern the mode of dehydration of hydroxyvinylidene derivatives [5] are still unclear. Moreover, it should be noted that dehydration, which most of the time is spontaneous, is the characteristic reaction of hydroxyvinylidene complexes; in contrast, elimination of ketones, which requires harsh conditions, has rarely been observed [6].…”

The reaction of Ru3(CO)12 with 1,4-dichloro-but-2-yne in basic methanolic solution. Synthesis and crystal structure of (μ-H)2Ru3(CO)9{μ3-η2-[H2CC(H)CCC(O)OCH3]}

“…These contain a CO bound both to one iron atom and to a carbon of the organic moiety. Reverse reactions, that is splitting of alkynols into cluster-bound acetylides and ketones have also been observed, both for ruthenium [12] and for iron [13].…”