α-Ketoacyl Complexes of Manganese Formed by Insertion of CO into a Manganese-Acyl Bond and by Nitrite Addition to a Manganese Carbyne Complex

John B. Sheridan, Arnold L. Rheinaold, John R. Johnson, Beth M. Handwerker, Gregory L. Geoffroy

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Abstract

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, le 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'(CO)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: P1̅, a = 6.928 (3), b = 7.425 (3), c = 16.153 (6) Å, α = 94.32 (3), β = 97.70 (3), γ = 110.73 (3)°, V = 763.3 (5) Å3, Z = 2, R(F) = 4.74%, P(wP) = 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.

Original languageEnglish (US)
Pages (from-to)2404-2411
Number of pages8
JournalOrganometallics
Volume7
Issue number11
DOIs
StatePublished - Nov 1988

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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