A New Allenyl Bonding Mode in Binuclear Complexes: Characterization and Molecular Structures of M2(CO)6(.mu.-PPh2)(.mu.-.eta.1:.eta.2.beta..gamma.-C(Ph():C:CH2) (M = Ru, Os)

Transformation of Dimetallacyclopentanes into β-Substituted Enamine-, Alkylidene-, and α,β-Unsaturated Acyl-Bridged Diiron Complexes

“…In contrast, while the η 1 -coordinated allenyl fragment appears to be unreactive toward nucleophilic reagents, such complexes readily undergo [2 + 3] cycloaddition reactions with electron-deficient olefins and, in the presence of Lewis acids, carbonyl compounds to give η 1 -cyclopentene (eq 3) and η 1 -2,5-dihydrofur-3-yl (eq 4) compounds, respectively . Since the discovery of rational, high-yield synthetic routes to binuclear allenyl complexes, which include the addition of diazoalkanes to μ−η 1 :η 2 -acetylides, S N 2‘ attack of a dimetalate at a propargyl halide, and template synthesis, a detailed examination of their reaction chemistry has revealed more disparate and varied reactivity patterns than their mononuclear counterparts. In this regard, examples of unusual coupling reactions (Scheme ), the addition of nucleophiles to C α , C β , and C γ (Scheme ), the formation of acyl−allenyl complexes via migratory insertion/elimination of CO into a μ−η 1 :η 2 -allenyl ligand (Scheme ), and the generation of diiron coordinated β,γ-unsaturated amides, esters, and ketones 14 (eq 5) all suggest that the σ−η-coordinated allenyl fragment offers immense potential as a building block for the synthesis of a wide range of unsaturated organic molecules, provided these products can be liberated from the metal center.…”

Synthesis of “Phosphine Tethered” η2-Allene and μ-η1:η2-Alkenyl Complexes: Facile P−Cα Bond Formation and C−H Activation Reactions of Bis(diphenylphosphino)methane with [Fe2(CO)6(μ-ER){μ-η1:η2α,β-(H)CαCβCγH2}] (E = PPh, R = Ph; E = S, R = tBu)

“…We have recently initiated a systematic investigation into the reactivity of the diiron allenyl complexes [Fe 2 (CO) 6 (μ-ER){μ-η 1 :η 2 α , β -(H)C α C β C γ H 2 }] (E = PPh, R = Ph, 1 ; E = S, R = t Bu, 2 ), and our efforts in this area have unveiled a wealth of unexpected reactivity toward monofunctional nucleophiles, including the generation of amido-functionalized alkenyl complexes via a novel amine−carbonyl−allenyl coupling sequence 8 and an unprecedented nucleophilic attack of primary and secondary phosphines at C α to afford, after 1,4-hydrogen migration, new phosphino-substituted μ-η 1 :η 2 -alkenyl ligands . In addition to these studies we are currently examining the reactivity of 1 and 2 with dppm to compare with [Ru 2 (CO) 6 (μ-PPh 2 ){μ-η 1 :η 2 -(Ph)C α C β  C γ H 2 }], which was reported to react via allenyl−carbonyl−phosphido coupling to afford a novel ketoallenyl phosphine …”

A new two-strand chain cluster: the synthesis and characterisation of [Os3(CO)11{μ3-η4-(C4H3S)C2C2(C4H3S)}] †

“…While the structure of cluster 2 is novel, it is related to that of the dinuclear allenyl clusters [M 2 (CO) 6 (µ-η 1 : η 2 -PhCCCH 2 )-(µ-PPh 2 )] (M = Ru 3a, Os 3b) 11 by the extension of the C and Os chains by one atom each. As such, these dinuclear clusters and 2 could be considered as members of the series of chain clusters M n (RC 2n Ϫ 1 R 2 ) and M n (RC 2n Ϫ 2 R) respectively, the n = 2 members of the second series being exemplified by the µ-η 2 -|| alkyne cluster [Os 2 (CO) 8 {C 2 (CO 2 Me) 2 }] 4.…”