137394-47-9Relevant academic research and scientific papers
Reactivity of 1-alkynes at dimanganese carbonyl centers. Synthesis and structural characterization of alkenyl-, alkenylidene-, alkynyl-, and 5-oxo-2-furanylidene-bridged dimanganese compounds
García Alonso, Francisco J.,Riera, Víctor,Ruiz, Miguel A.,Tiripicchio, Antonio,Camellini, Marisa Tiripicchio
, p. 370 - 386 (2008/10/08)
The new unsaturated hydride [Mn2(μ-H)2(CO)6(μ-dppm)] (1) is prepared by treatment of [Mn2(μ-Cl)2(CO)6(μ-dppm)] with 4 equiv of Li[HBEt3] in tetrahydrofuran at room temperature. 1 reacts with 1-alkynes (R = H, Ph, tBu, COOMe) at room temperature to give either hydrido-alkenyl complexes [Mn2(μ-H)(μ2,η1,η 2-CR=CH2)(CO)6(μ-dppm)] (R = H (3a), Ph (3b)) or alkenylidene species [Mn2-(μ,η1η2-C=CH tBu)(CO)6(μ-dppm)] (4c) and [(CO)3Mn(μ-dppm)]{μ-C=CHC(O)OMe}Mn(CO)3] (6). The photochemical reaction of [Mn2(CO)8(μ-dppm)] (2) with 1-alkynes (R = H, Ph, tBu, CH3OCH2) at -20°C results in the formation of vinylidene [Mn2(μ,η1,η2-C=CHR)(CO) 6(μ-dppm)] (R = Ph (4b), tBu (4c), CH3OCH2 (4d)), hydrido-alkynyl [Mn2(μ-H)(μ,η1,η2-C 2R)(CO)6(μ-dppm)] (R = H (5a), Ph (5b), tBu (5c), CH3OCH2 (5d), or 5-oxo-2-furanylidene complexes [(CO)4Mn(η,-dppm){μ,η1,η 4-C-CH=C(R)C(O)O)Mn-(CO)2] (R = H (7a), CH3OCH2 (7d)) and [Mn2(μ-CO){μ2,η1,η 1-C-CH=C(R)C(O)O}(CO)6(μ-dppm)] (R = H (8a), CH3OCH2 (8d)). The relative amounts of the above species depend strongly on the nature of the alkyne and the reaction solvent. The 5-oxo-2-furanylidene ligands in 7 bind the dimetal moiety in a novel μ2η1,η4-fashion acting as a 6-electron donor. The alkenylidene complexes 4b and 4c can also be obtained through UV irradiation of the alkenyl complex 3a in the presence of an excess of 1-alkyne (R = Ph, tBu). Unexpectedly, these complexes isomerize spontaneously in solution at room temperature to yield the corresponding hydrido-alkynyls 5b and 5c. The latter regenerate their vinylidene precursors 4b and 4c by treatment with Li[AlH4] followed by addition of HBF4 to the resulting mixture. Complexes 3a, 5a-d, and 7 are stereochemically nonrigid in solution. In the case of the alkynyl species 5 the fluxional process appears to be especially fast, as even evidence for incipient coalescence is not observed down to -90°C. The structures of 4c, 5b, 6, 7d, and 8d have been fully elucidated by X-ray diffraction studies.
