Reactivity of multi-site bound allenylidene towards alkynes and silica gel †

Reaction of Fe3(CO)12 with but-2-yn-1,4-diol, 1,4-dichloro-but-2-yne, propargyl-alcohol and propargyl-chloride.

“…To our knowledge there is only one other structural study for Fe 2 (CO) 6 (C 28 H 16 ) (1a) [26], while for Fe 2 (CO) 6 [Ph 2 C@C@C@CPh 2 ] (1b) only preliminary and doubtful data are reported in [27]. Both complexes contain heavily substituted ligands and have been obtained through thermal reactions whereas 1 (obtained in better yields under thermal conditions) represents the unsubstituted parent structure.…”

“…The complex 5 shows a ''ferrole-like'' structure homologue to Fe 2 (CO) 6 {Ph(H)CCCHC(OMe)O} (5a) [3]. The formation of complex 5 and of 5a containing a methoxy carbonyl group requires the activation of CO and of methanol; we could, indeed, evidence that complex 5a was formed upon the reaction of the (Type I) allenylidene [Fe 3 (CO) 9 (l-CO){C@C@C(H)Ph}] (complex 3a, homologue of 3) with the methanol used to stabilize the iron carbonyl [3].…”

“…A molecule of PA, bonded to the CO, has undergone dehydroxylation and uptake of methanol; the latter splits into the CH 3 O group, which formally substitutes the lost OH, and one hydrogen atom which is bound to the three-carbon atom chain. This behaviour is not uncommon for methanol [1] The complex is formed by a Fe 2 (CO) 6 frame with a Fe-Fe distance of 2.6102(8) Å . Three terminal CO groups are bound to each iron atom and two of them are disposed in eclipsed way.…”

“…In addition, methanol may react with the tri-iron allenyl complexes of type I undergoing splitting into H and CH 3 O fragments to form compounds homologues of complex Fe 2 -(CO) 6 {H 2 CCC(H)C(OMe)O} reported in this paper [3]. Last, but not least, we have found that dehydration of cluster-bound alkynols (M = Ru) [4] is favoured by silica gel and that interconversions between allenylidene (type I) and vinyl-acetylide complexes (type II) on triruthenium clusters occur under acidic conditions [5] and that alumina and silica gel promote the interconversion and carbon-carbon coupling reactions of allenylidenes bound to triruthenium clusters [6,7].…”

Syntheses and molecular structures of Ru3(μ-H)(μ3-CPh2CCCCPh)(CO)9 and Ru3{μ3-CPhCHCC(CPh2)CHCPh}(μ-CO)(CO)8

“…A common precursor of the allenylidene clusters is the alkyne complex Ru 3 (l-H){l 3 -C 2 CPh 2 -(OH)}(CO) 9 (1) which, with HBF 4 Á OMe 2 rearranges by migration of OH to the cluster to give allenylidene 2 (Scheme 1). Since then, several accounts of their reactivity have appeared [4][5][6], including studies of their reactions with alkynes [7][8][9]. Two major types of product were obtained upon reaction of 2 with alkynes, containing either one (3) or two alkyne molecules (4) [8].…”