106865-72-9Relevant academic research and scientific papers
α-Ketoacyl complexes of manganese formed by insertion of CO into a manganese-acyl bond and by nitrite addition to a manganese carbyne complex
Sheridan, John B.,Johnson, John R.,Handwerker, Beth M.,Geoffroy, Gregory L.,Rheingold, Arnold L.
, p. 2404 - 2411 (2008/10/08)
The carbyne complex [Cp′(CO)2Mn≡CR]+ (Cp′ = C5H4Me; R = Ph, Tol) cleanly reacts with NO2- to form the α-ketoacyl complex Cp′(CO)(NO)Mn - C{O}C{O}R (4). A similar reaction of [Cp(CO)2Re≡CTol]+ with NO2- gives the acyl complex Cp(CO)(NO)Re - C{O}Tol (3). α-Ketoacyl complex 4 has also been prepared by oxidation of [Cp′(CO)2Mn-C{O}R]- to form the 17e complex Cp′(CO)2Mn - C{O}R (8) followed by its reaction with NO gas. The latter reaction is the first demonstration of the insertion of CO into a metal-acyl bond. A mechanism is proposed for this process involving the addition of NO to 8 to give Cp′(CO)2-(NO)Mn - C(O)R with a bent, 1e nitrosyl ligand which then inserts CO into the Mn-acyl bond as the nitrosyl relaxes to the more common linear, 3e form. The proposed intermediate 8 can also be obtained from the carbene complex Cp′(Cp)2Mn=C(ONO)R, which forms by addition of NO2- to [Cp′(CO)2Mn≡CR]+, and accounts for the formation of 4 in this latter reaction. Complex 4a (R = Tol) has been crystallographically characterized: P1, a = 6.928 (3), b = 7.425 (3), c = 16.153 (6) A?, α = 94.32 (3), β = 97.70 (3), γ = 110.73 (3)°, V = 763.3 (5) A?3, Z = 2, R(F) = 4.74%, R(wF) = 5.25% for 1855 reflections with Fo > 3σ(Fo). The molecule has the usual three-legged piano-stool geometry characteristic of CpMnL3 complexes, and the α-ketoacyl ligand is bound in an η1 fashion. The α-ketoacyl ligand adopts an s-trans configuration with a dihedral angle of 78° between the planes defined by the two carbonyl groups and their substituents. Complex 4 readily undergoes substitution reactions with L = PPh3 and C≡N-t-Bu to form the α-ketoacyl complexes Cp′(NO)(L)Mn-C{O}C{O}R, but no deinsertion of CO from the α-ketoacyl ligand to form an acyl complex was observed for 4 nor its substituted derivatives under any conditions examined. The rhenium-acyl complex 3 was alkylated to form the cationic carbene complex [Cp(CO)(NO)Re=C(OMe)Tol]+ which readily re-forms 3 upon reaction with H2O.
