Insertion of imines and carbon monoxide into manganese-alkyl bonds: Synthesis and structure of a manganese-alpha-amino acid derivative

Citation
D. Lafrance et al., Insertion of imines and carbon monoxide into manganese-alkyl bonds: Synthesis and structure of a manganese-alpha-amino acid derivative, ORGANOMETAL, 20(6), 2001, pp. 1128-1136
Citations number
48
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
ORGANOMETALLICS
ISSN journal
0276-7333 → ACNP
Volume
20
Issue
6
Year of publication
2001
Pages
1128 - 1136
Database
ISI
SICI code
0276-7333(20010319)20:6<1128:IOIACM>2.0.ZU;2-Q
Abstract
Two new routes have been developed to generate manganese-chelated amides fr om imine and carbon monoxide building blocks. The reaction of (CO)(5)MnR (R = CH3, Ph) with (p-tolyl)(R-1)= NR2 (R-1) = NR2 (R-1 = H,tBu; R-2 = alkyl, H) results in the generation of the cyclometalated imine complexes (CO)(4) Mn[eta (2)-4-CH3-2-(C(R-1)=NR2)-C6H3] in 50-84% isolated yield. However, wh en the reaction of (p-tolyl)(H)C=NCH3 with (CO)(5)MnCH3 is performed in the presence of AlCl3, the product of sequential carbon monoxide and imine ins ertion is generated in 35% yield: (CO)(4)Mn[eta (2)-C(H)(p-tolyl)N(CH3)COCH 3], The addition of PPh3 to the latter complex results in replacement of a carbonyl ligand and formation of the isolable fac-(CO)(3)(PPh3)Mn[eta (2)-C (H)(p-tolyl)N(CH3)COCH3], In an alternative route to metal-bound amides, th e oxidative addition of the N-acyl iminium salt (p-tolyl(H)C=N(CH3)COPh+Cl- to (CO)(5)Mn-Na+ has been found to lead to the generation of the product o f subsequent CO insertion, (CO)(4)Mn[eta (2)-COC(H)(p-tolyl)N(CH3)COPh]. Th e latter represents the first example of a acyl-bound transition-metal-chel ated a-amino acid complex and has been characterized by X-ray crystallograp hy. Preliminary reactivity studies demonstrate that (CO)(4)Mn[eta (2)-COC(H )(p-toyl)N(CH3)COPh] reacts with PPh3 to generate the unchelated cis-(CO)(4 )(PPh3)Mn[COC-(H)(p-tolyl)N(CH3)COPh], while reaction with NaBH4 leads to t he liberation of the amide (p-tolyl)CH2N(CH3)COPh, rather than the amino ac id residue.