Carbonyl‐Komplexe von Chrom, Molybdän und Wolfram mit Isocyanacetat. Reaktionen am koordinierten Isocyanacetat. Stabilisierung von Isocyanessigsäure und Isocyanacetylchlorid am Metall. Isocyanopeptide [1]

Abstract

Abstract Carbonyl Complexes of Chromium, Molybdenum and Tungsten with Isocyano Acetate. Reactions of Coordinated Isocyanoacetate. Stabilization of Isocyanoacetic Acid and Isocyanoacetyl Chloride at the Metal Atom. Isocyanopeptides The reactions of [(OC) 5 MCNCH 2 CO 2 Et] (M = Cr, W) with Na[N(SiMe 3 ) 2 ] or with KOH afford the isocyanoacetate complexes [(OC) 5 MCNCH 2 CO 2 ] − ( 1,2 ). Similarly, the complex [(OC) 3 Mo(CNCH 2 CO 2 − Li + ) 3 ] ( 4 ) was obtained from [(OC) 3 Mo(CNCH 2 CO 2 Et) 3 ] ( 3 ) and LiOH. Protonation of 1 and 2 affords the sublimable isocyanoacetic acid complexes [(OC) 5 MCNCH 2 CO 2 H] ( 5 , 6 ; M = Cr, W) in which the functional isocyanide is stabilized at the metal atom. Reactions of [(OC) 5 WCNCH 2 CO 2 − K + ] and of [(OC) 3 Mo(CNCH 2 CO 2 − Li + ) 3 ] with oxalyl dichloride give the isocyanoacetyl chloride compounds [(OC) 5 WCNCH 2 COCl] ( 9 ) (sublimable) and [(OC) 3 Mo(CNCH 2 COCl) 3 ] ( 10 ); the latter ( 10 ) was not isolated. Complexes 9 and 10 were reacted in situ with β‐alanine, glycine, phenylalanine and methionine esters as well as the peptide esters GlyGlyOEt, PhePheOMe, Phe‐β‐AlaOMe, and GlyGlyGlyOMe to form the isocyanoacetyl amino acid esters ( 11 ‐ 14 ) and the isocyanoacetyl peptide esters ( 15 ‐ 18 ) which are stabilized at the molybdenum atom.