Insertion of Imines and Carbon Monoxide into Manganese−Alkyl Bonds:  Synthesis and Structure of a Manganese−α-Amino Acid Derivative

Abstract

Two new routes have been developed to generate manganese-chelated amides from imine and carbon monoxide building blocks. The reaction of (CO) 5 MnR (R ) CH 3 , Ph) with (ptolyl)(R 1 )dNR 2 (R 1 ) H, t Bu; R 2 ) alkyl, H) results in the generation of the cyclometalated imine complexes (CO) 4 Mn[η 2 -4-CH 3 -2-(C(R 1 )dNR 2 )-C 6 H 3 ] in 50-84% isolated yield. However, when the reaction of (p-tolyl)(H)CdNCH 3 with (CO) 5 MnCH 3 is performed in the presence of AlCl 3 , the product of sequential carbon monoxide and imine insertion is generated in 35% yield: (CO) 4 Mn[η 2 -C(H)(p-tolyl)N(CH 3 )COCH 3 ]. The addition of PPh 3 to the latter complex results in replacement of a carbonyl ligand and formation of the isolable fac-(CO) 3 (PPh 3 )-Mn[η 2 -C(H)(p-tolyl)N(CH 3 )COCH 3 ]. In an alternative route to metal-bound amides, the oxidative addition of the N-acyl iminium salt (p-tolyl(H)CdN(CH 3 )COPh + Clto (CO) 5 Mn -Na + has been found to lead to the generation of the product of subsequent CO insertion, (CO) 4 Mn-[η 2 -COC(H)(p-tolyl)N(CH 3 )COPh]. The latter represents the first example of a acyl-bound transition-metal-chelated R-amino acid complex and has been characterized by X-ray crystallography. Preliminary reactivity studies demonstrate that (CO) 4 Mn[η 2 -COC(H)(ptolyl)N(CH 3 )COPh] reacts with PPh 3 to generate the unchelated cis-(CO) 4 (PPh 3 )Mn[COC-(H)(p-tolyl)N(CH 3 )COPh], while reaction with NaBH 4 leads to the liberation of the amide (p-tolyl)CH 2 N(CH 3 )COPh, rather than the amino acid residue.

The role of phosphine in cobalt-catalyzed carbonylative polymerization of N-alkylaziridine

“…In 1997, Sen [35,36] reported an oxidative carbonylative polymerization producing polysuccinates. Further, in 1998, Sen and Arndtsen independently proposed the COimine copolymerization as a way of synthesizing polypeptides [37][38][39]. Although the copolymerization proposed by Sen and Arndtsen has yet to be realized, they demonstrated the first example of stoichiometric imine insertion into metal-acyl bonds, a necessary reaction for the copolymerization to occur.…”

N- vs O-Coordination in cyclomanganation of 1,5-diaryl-3-(2-pyridyl)pentane-1,5-diones and 3-(2-pyridyl)chalcones; cyclomanganation at saturated carbon and the crystal structure of [1,5-diphenyl-κC2-3-(2-pyridyl- κN)pentan-2-yl-κC2-1,5-dione-κO1κO5]tetracarbonylmanganesetricarbonylmanganese

“…Other cyclomanganated compounds with Mn bonded to saturated carbon are known [4][5][6][7], including some a to (ester) carbonyl groups [4], but none are formed by direct manganation, e.g., 14 is formed from ortho-mang-…”

A Fischer Carbene within an Arduengo Carbene

“…Note that intermediates I and II allow a reasonable explanation for the formation of isomer 3 a as a kinetic product, although they were not detected during the course of the reaction. In fact, the Mn1 À C5 (1.96 (2) ) bond length is slightly shorter than that usually found for Mn À C single bonds (2.12 ), [13] and the C5 À O7 distance (1.26 (2) ) is lengthened from that typically encountered in acyl complexes or in amide molecules (1.21 ), [13,14] therefore supporting some contribution by the carbene-like form of the carbamoyl fragment. [12] The X-ray crystal structure shows that the new diazamangana-heterocycle species formed features a carbamoyl fragment.…”