Aminomethyl and Aminoacetyl Complexes of Palladium(II), Platinum(II), Iron(II) and Rhenium(I) with N‐Phthaloyl as Amino Protecting Group and Mechanistic Studies on the Palladium‐Catalyzed Amidocarbonylation

Abstract

AbstractNew aminomethyl and aminoacetyl complexes with N‐phthaloyl as the amino protecting group were synthesised by oxidative addition of N‐phthaloylmethyl or ‐acetyl halide to carbonylmetallates or to Pd(PPh3)4 or [Pt(C2H4)(PPh3)2] to give [Re{C(O)CH2N‐phthaloyl}(CO)5] (1), [FeCp(CH2N‐phthaloyl)(CO)2] (2), [FeCp{C(O)CH2N‐phthaloyl}(CO)2] (3), trans‐[PdBr(CH2N‐phthaloyl)(PPh3)2] (4) and trans‐[Pd{C(O)CH2N‐phthaloyl}(X)(PPh3)2] (X = Br, Cl; 5, 6). The bis(phosphane) complexes [Pd(CH2N‐phthaloyl)(X)(R2PCH2CH2PR2)] and [Pd{C(O)CH2N‐phthaloyl}(X)(R2PCH2CH2PR2)] (X = Cl, Br; R = Ph, C6H11) 8−13 were obtained by ligand exchange from 4, 5 or 6 with the corresponding bis(phosphanes). Halide abstraction from 4, 5, 6, 10, 11 or 12 gives the cationic complexes 14 and 15 with formation of a five‐membered chelate ring which includes one carbonyl atom of the phthaloyl group. The reaction of 6 with the tridentate ligand PhP(CH2CH2PPh2)2 affords the five‐coordinate complex 16 and from [Pt(C2H4)(PPh3)2] and organic halides the platinum(II) complexes trans‐[Pt(CH2N‐phthaloyl)(Cl)(PPh3)2] (17) and [PtC(O)CH(CH2Ph)N‐phthaloyl(Cl)(PPh3)2] (18) were isolated. The structures of 2, 11, 14, 15 and 16 were determined by single‐crystal X‐ray analysis. The mechanism of the palladium‐catalysed amidocarbonylation was studied using phthalimide, formaldehyde and CO as a model system which gives N‐phthaloylglycine in good yield. The proposed elementary steps in the palladium‐catalysed amidocarbonylation could be verified by use of the possible intermediates phthaloyl‐NCH2OH and phthaloyl‐NCH2Br as substrates, by oxidative addition of phthaloylmethyl bromide to Pd0, by insertion of CO into the palladium‐carbon‐bond of 4 and 8 with formation of 5 or 9, respectively, and by use of the isolated possible intermediates 4, 5 and 14 as catalysts. Thus, all crucial steps of the palladium‐catalysed amidocarbonylation with the model system phthalimide/formaldehyde/CO have been verified for the first time. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)