Understanding Selectivity in the Oxidative Addition of the Carbon−Sulfur Bonds of 2-Cyanothiophene to Pt(0)

A DFT Comparison of C-C Reductive Coupling from Terminal Cyanido and Cyaphido Complexes of Nickel

The density functional theory study of the thermal C-C reductive coupling from terminal cyanido and hypothetical cyaphido complexes of [Ni(dmpe)] (dmpe = 1,2-bis(dimethylphosphino)ethane) revealed the key reaction intermediate in the reductive C-CP coupling being a σ-CC complex unlike an η2-aryl complex in the Ni C-CN system, as already observed in our previous studies. The reaction in THF is endothermic by 4.9 kcal/mol for cyanido with a 32.0 kcal/mol activation barrier and exothermic by 28.5 kcal/mol for cyaphido with an 11.3 kcal/mol activation barrier. To compare our results with the existing experimental data, we chose mesityl as the aryl group and also studied the CP reaction with [Pt(dmpe)] and [Pt(dmpm)] (dmpe = 1,2-bis(dimethylphosphino)methane) fragments. Our findings are consistent with the thermodynamically uphill photolytic C-CP bond activation in phosphaalkynes with Pt and a faster thermal back-reaction with [Pt(dmpe)] compared to that of [Pt(dmpm)]. Based on the natural population analysis, when the polarity of the C-C bond is inverted, the sign of ΔG° is also inverted.

Ligand isomerism in Pt(II) complexes – structural aspects

This review has focused on ligand isomers in Pt(II) complexes. There are a variety of inner coordination spheres about the platinum(II) atom (PtN4, PtN2Cl2, PtP2Cl2, PtPNC2, PtPNCl2, PtP2CBr, PtP2CS), build up by mono- and bidentate ligands. The bidentate ligands create a variety of metallocyclic rings. The L–Pt–L bite angle (mean values) open in the sequence: 73.1° (PNP) < 78.7° (NC2C) < 80.4° (NC2N) < 86.4° (PC2P) < 86.7° (PNNP) < 93.0° (CC3S). There are three types of isomers: ligand, mixed – (ligand + distortion), and mixed – (ligand + cis-trans), isomers, which are rarity.

Recent advances in well-defined, late transition metal complexes that make and/or break C-N, C-O and C-S bonds

Chemical transformations that result in either the formation or cleavage of carbon-heteroatom bonds are among the most important processes in the chemical sciences. Herein, we present a review on the reactivity of well-defined, late-transition metal complexes that result in the making and breaking of C-N, C-O and C-S bonds via fundamental organometallic reactions, i.e. oxidative addition, reductive elimination, insertion and elimination reactions. When appropriate, emphasis is placed on structural and spectroscopic characterization techniques, as well as mechanistic data.

Competitive carbon-sulfur vs carbon-carbon bond activation of 2-cyanothiophene with [Ni(dippe)H]2

The processes of C-C and C-S bond cleavage have been studied with the homogeneous organometallic compound [Ni(dippe)H](2) (1). When 1 is reacted with 2-cyanothiophene at room temperature, cleavage of the nitrile-substituted C-S bond occurs, forming the Ni-metallacycle complex (dippe)Ni(kappa(2)-S,C-SCH=CHCH=C(CN)) (2a), which has been fully characterized by NMR spectroscopy and X-ray diffraction. 2a was converted to the C-CN cleavage product (dippe)Ni(CN)(2-thiophenyl) (3) when heated in solution. On closer inspection, four other intermediates were observed by (31)P NMR spectroscopy at low temperature. Structures for the intermediates were elucidated through a combination of independent synthesis, theoretical calculations, chemical characterization, and experimental precedent. A kinetic product (dippe)Ni(kappa(2)-S,C-SC(CN)=CHCH=CH) (2b) was formed from cleavage of the nonsubstituted C-S bond, as well as a Ni(0) eta(2)-nitrile intermediate, (dippe)Ni(eta(2)-C,N-2-cyanothiophene) (4), and a dinuclear mixed Ni(0)-Ni(II) product (6b). A complete DFT analysis of this system has been carried out to reveal comparative details about the two bond cleavage transition states.

Platinum complexes of eta2-thiophenes

Two novel ligands, 3,4-bis(quinolin-8-yl)thiophene and 3,4-bis[6-(trifluoromethoxyl)quinolin-8-yl]thiophene, and their corresponding diplatinum complexes have been synthesized and fully characterized. These two complexes feature the inverse sandwich structures and the eta(2)-C,C thiophenes on platinum centers.