Novel Cyclopalladated Imino-thiophenes: Synthesis and Reactivity Toward Alkynes and Carbon Monoxide

Abstract

ortho-palladated complexes based on thiophene and benzothiophene ligands 1a and 1b have been synthesized by direct C–H activation under mild conditions. These species were fully characterized, including single-crystal X-ray diffraction analysis. The reactions of these novel complexes with internal alkynes afforded a variety of thieno[3,2-c]pyridinium salts substituted at the 6- and 7-positions. The thiophene-based complex 2a also reacts with carbon monoxide, in the presence of different alcohols, forming the corresponding esters by tandem alkoxycarbonylations. This latter reaction can be exploited for the unexpected, but straightforward, formation of the monomeric bis-cyclometallated complexes 6a and 6b from 2a or 2b, whose syntheses do not require the employment of transmetallating agents. The structures of these monomeric palladacycles were also fully elucidated by means of X-ray diffraction studies.

Selectivity in metal–carbon bond protonolysis in p-tolyl- (or methyl)-cycloplatinated(ii) complexes: kinetics and mechanism of the uncatalyzed isomerization of the resulting Pt(ii) products

“…Cyclometallated complexes are of continuing interest due to the possibility of their diverse applications in industrial and medical technologies. [1][2][3][4][5][6][7][8][9][10] In this regard, platinum complexes have been extensively investigated and indicated to have medicinal applications due to their cytotoxicity and luminescence properties. [11][12][13][14][15][16][17][18][19][20][21] We have recently reported some new C,N donor cycloplatinated(II) complexes with bisphosphine ligands, such as dppm = bis(diphenylphosphino)methane or dppa = bis(diphenylphosphino)amine, and indicated that they have significant capabilities of being further investigated as anticancer drugs.…”

Palladium-Mediated Functionalization of Benzofuran and Benzothiophene Cores

“…As mentioned in the Introduction, no palladacycles derived from a primary arylalkylamine containing either the benzofuran or the benzothiophene ring have been described previously. Moreover, there are only two precedents of similar C , N -palladacycles with the metal at the C3 position of the benzothiophene ring, and in both cases, the nitrogen atom belongs to an imine fragment. , …”

“…These examples included: (1) For the benzofuran nucleus: (1a) C , N -, C , S -, , or C , Se -five-membered palladacycles metalated at the C3 position; and (1b) C , N -six-membered palladacycles metalated at C3 . (2) For the benzothiophene nucleus: (2a) C , N -five-membered palladacycles metalated at C3, where the nitrogen atom belongs to an imine or a pyridine moiety, (2b) S , C , N -pincer derivatives containing two five-membered rings, and (3b) C , N -five- or six-membered palladacycles metalated at the C2 position, being the nitrogen part of an imine fragment. , …”

3,4-Dimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline and the 1-(1-thiophen-2-yl) analogue

“…To the best of our knowledge, only a limited number of mono(imino)pyrrole compounds have been reported in the literature (Dawson et al, 2000;Anderson et al, 2006;Carabineiro et al, 2007;Pé rez-Puente et al, 2008). The case is similar for mono(imino)thiophene compounds (Cuesta et al, 2011), in which most of the side arms of the heterocyclic rings were H atoms. To simulate the original structure of a bis(imino)pyridine ligand, we chose to replace an H atom with a methyl group and thus prepare new heterocyclic imino compounds.…”