Metallkomplexe mit biologisch wichtigen Liganden, CXXI [1]. Orthopalladierte Enolate aus N-(Diphenylmethylen)-Schiff-Basen von a-Aminosäureestern als ambivalente 1,3-Dipole in [2+3]-Cycloadditionsreaktionen. Strukturen einer Reihe von Cycloaddukten

Abstract

Enolates of ortho-palladated N-(diphenylmethylene) Schiff bases from glycine esters (R3P)Pd[(C6H4)(C6H5)C=N-C(R')=CO2R] were isolated and have been shown to be ambivalent 1,3-dipoles in [2+3] cycloadditions. Tetracyanoethene, dimethyl acetylene dicarboxylate, dimethyl azodicarboxylate, thiobenzophenone, thione-S, 4-phenyl-l,2,4-triazoline-3,5-dione, diphenyl-ketene and phenylisocyanate are added at the palladium and the enolate (a-C) carbon atoms, whereas methyl propiolate, methyl acrylate, and the methyl esters of maleic and fumaric acid form [2+3] cycloadducts with the «-carbon and the imino carbon atoms of the enolates under mild conditions. The structures of seven cycloadducts were determined by X-ray diffraction analyses.

Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: synthesis, characterization and reactivity. Crystal and molecular structures of [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)] and [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{µ-Ph2P(CH2)4PPh2}][CF3SO3]2

“…For the convenience of the reader, the compounds and reactions are shown in Schemes 1 and 2. The compounds described in this paper were characterised by elemental analysis (C, H, N), IR spectroscopy (data in the Experimental section), 1 H, 31 P-{ 1 H} (see Table 1) and, in part, 13 shifted to lower frequency due to coordination of the imine group to the palladium atom via the lone pair of the nitrogen atom. 32 Coordination of the palladium atom to the C=N moiety is confirmed by the shift to lower wavenumbers of the n(C=N) band in the IR spectrum (1635s, 1, 1613sh s cm À 1 , 2).…”

“…Among these, cyclometallated complexes derived from potentially terdentate [C,N,N] and [C,N,S] ligands have been described. [12][13][14][15][16][17][18][19][20][21][22][23] In previous work, we have shown that potentially terdentate ligands, such as Schiff bases I, [24][25][26][27] semicarbazones II 28,29 and thiosemicarbazones III, 30,31 undergo facile metallation with palladium(II), palladium(0) and platinum(II) to give compounds with two fivemembered fused rings at the metal centre. The Schiff base and semicarbazone derivatives are monomeric species but the complexes derived from thiosemicarbazones present a tetranuclear structure.…”

Cyclopalladated complexes with N-(benzoyl)-N′-(2,4-dimethoxybenzylidene)hydrazine: syntheses, characterization and structural studies

“…Thus there is a continuing quest for new cyclometallated species with different types of ligands. Compounds containing two non-carbon donor atoms are well known to act as tridentate ligands for palladium(II) or platinum(II) via ortho-metallation and can produce cyclometallated complexes having two fused rings at the metal centre [12][13][14][15][16][17][18][19][20][21][22][23]. Thiosemicarbazones and semicarbazones of aromatic aldehydes belong to this type of ligands [18][19][20][21].…”

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…[610] By mentioning the extensive studies of metal catalyzed [3+2]-cycloadditions of azomethine ylides (prepared from Schiff bases of amino acid esters and aromatic carbonyl compounds) with activated olefins to give pyrrolidines (Equation (43)), [611][612][613][614][615] we are aware of going far beyond the scope of this review. Just for the record, none of the D1b-type metallo-azomethine ylides 146 has ever been isolated, however essential they are in this kind of processes.…”

“…Dimethyl acetylene dicarboxylate, for example, adds across the pallada-dipole to give complex 148, whereas the [3+2]-cycloaddition with methyl acrylate resulted in the tricyclic system 149 (Equation (44)). [614] . The "azomethine ylide character" of pyrroles was exploited by osmium(II)-, rhenium(I)-and tungsten(0)-promoted 1,3-dipolar cycloaddition reactions with dimethyl fumarate, which resulted in the formation of 7-azanorbornene complexes.…”