A computational study utilizing density functional theory (DFT) was performed to analyze the mechanism of ethylene dimerization catalyzed by (P,N) nickel(II) complexes, where (P,N) is a mixed phosphine–iminophosphorane ligand. Two plausible reaction pathways were considered, namely the Cossee and metallacycle pathways, for three model systems. The fundamental role of ligand assymetry and the importance of steric and trans effects were elucidated. In order to discriminate between both mechanisms, the activation of the precatalyst by trimethylaluminum was modeled. The results obtained allow the establishment of useful guidelines for creating new specifically tailored nickel-based catalysts for controlled dimerization.

Cross-coupling reactions can be efficiently catalyzed using palladium complexes. The formation of low-coordinated, highly reactive Pd(0), which is believed to be the catalytic species, is critical. The mechanism of the reduction of a stable and readily available allyl Pd(II) complex into Pd(0) by a combination of K2CO3 and PhB(OH)(2) has been studied. We report on the characterization of the associated reactive solution using a combination of density functional theory and experimental methods. First, the stoichiometric reaction of an (allyl)(phosphine)palladium(II) complex with K2CO3 was first investigated using trandem mass spectrometry. A palladium-carbonate complex could be characterized in the electrospray mass spectrum of the reactive solution. Gas-phase infrared spectra of mass-selected complexes have been recorded, giving further information on the coordination mode (kappa(1)) of the carbonate ligand. This structural information derived from spectroscopy is critical because the relative energy of the two kappa(1) and kappa(2)-carbonate isomers is difficult to determine theoretically, presumably because of the charge transfers at play between the carbonate and the palladium. Second, the product of the stoichiometric addition of PhB(OH)(2) to this carbonate complex was investigated. Both P-31 and H-1 NMR data provide compelling evidence for the formation of the desired 14-electron Pd(0) complex.

A new protocol for the direct cobalt-catalyzed vinylation of aryl halides using β-halostyrene has been developed in order to form functionalized stilbenes. A variety of aromatic halides featuring different reactive group were employed. This method proceeded smoothly with a total retention of the double bond configuration in the presence of triphenylphosphine as ligand. Preliminary DFT calculations rationalize these results and proposed a reaction pathway in agreement with the experimental conditions. This procedure offers a new route to the stereoselective synthesis of stilbenes.

The reactivity of both the monoanionic and dianionic forms of bis(diphenylthiophosphinoyl)methane (2– and 22–) as well as the dianion of tetraisopropyl methylenediphosphonate(32–) was investigated towards the same CoII precursor CoCl2. Monoanion 2– coordination yields a homoleptic zwitterionic CoII complex. However, both dianions (22– and 32–) give the same overall structure with a square Co2C2 core. Structures of all of the complexes have been confirmed by full NMR spectroscopic analysis and X-ray diffraction. Furthermore, DFT calculations have been carried out to rationalize the stability of such species.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The catalytic activity both of cationic [(XDPP)Au][X] (XDPP = bis-2,5-diphenylphosphole xantphos X = BF(4)) and of the isolated gold hydride complex [(XDPP)(2)Au(2)H][OTf] in the dehydrogenative silylation process is presented. A parallel theoretical study using density functional theory revealed a mechanism involving the counter anion as a co-catalyst, which was experimentally confirmed by testing various counterions (X = OTf, NTf(2), PF(6)). Finally, a "Au(2)H(+)" species was determined as the intermediate during the catalytic cycle, which correlates well with the experimental findings on the first example of catalytic activity of an isolated "Au-H" complex.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A phosphorus analog of salen ligands featuring iminophosphorane functionalities in place of the imine groups was synthesised in 2 steps from o-diphenylphosphinophenolvia the preparation of the corresponding bis-aminophosphonium salt. This novel tetradentate ligand (1), which we named phosphasalen, was coordinated to Pd(II) and Ni(II) metal centres affording complexes 6 and 7 respectively, which were characterised by multinuclear NMR, elemental and X-ray diffraction analyses. Both neutral complexes adopt a nearly square-planar geometry around the metal with coordination of all iminophosphorane and phenolate moieties. The electronic properties of these new complexes were investigated by cyclic voltammetry and comparison with known salens was made when possible. Moreover, the particular behaviour of the phosphasalen nickel complex 7 was further investigated through magnetic moment measurements and a DFT study.

Tetradentate iminophosphorane complexes [RuH(PNNP)][BAr4F] (5) and [RuHCl(PNNP)] (6) (PNNP = PPh2CH2PPh2NCH2CH2NPPh2CH2PPh2), prepared by in situ deprotonation of the aminophosphonium ligands in the presence of the dihydrogen complex RuH(H-2)-(Cl)(PCy3)(2), are active precatalysts for the catalytic transfer hydrogenation of ketones at 80 degrees C under basic conditions in (HOPr)-Pr-i. Complex 6 was characterized by X-ray diffraction. With a predominant focus on acetophenone, a comparative study with [RuH(H2NNPP)(PCy3)][BAr4F] (3) incorporating a tridentate ligand (H2NNPP = H2N(C6H4)NPPh2CH2PPh2) does not indicate an NH effect. It is postulated that the pentacoordinated configuration around Ru with a hydride trans to a vacant site is essential in the catalyst resting state; however, the stability of this structural arrangement is disadvantageous for high activities. Further mechanistic studies, including labeling experiments, indicate facile protonation of these systems and, in addition, structural variations as a function of protonating agent ((HOPr)-Pr-i, HX, H2O). The hydrido(chloro) complex RuH(Cl) (HNP) (NP) (7) (NP = (Ph2PCH2PPh2NCH2Bu)-Bu-t) was also isolated and characterized by X-ray diffraction, and a hydrogen bond between the chlorine and the NH group of the pendant ligand was ascertained by DFT calculations.

The mono-, bis-, and tris-carbene uranium complexes [Li(THF)(2)U(SCS)Cl-3(THF)] (2a), [U(SCS)(2)(THF)(2)] (3a), and [{Li(OEt2)}(2)U(SCS)(3)] (1) were synthesized in good yields by reactions of UCl4 and the stoichiometric amount of Li-2(SCS) [(SCS)(2-) = [Ph2P(=S)](2)C2-. Complex 3a was also obtained by comproportionation reaction of 1 and 0.5 molar equiv of UCl4 and further reacted with 1 molar equiv of UCl4 to give the neutral mono-carbene [U(SCS)Cl-2(THF)(2)] (5a). Treatment of U(NEt2)(4) with H2C(Ph2PS)(2) in THF led to a mixture of 3a and [U(SCS)(NEt2)(2)] (6), while the same reaction in Et2O gave the mixed alkyl-carbene compound [U(SCS)(SCHS)(NEt2)] (7) in 85% yield. The cationic uranium carbene complex [U(SCS)(NEt2)(THF)(3)][BPh4] (9) was isolated in almost quantitative yield from reaction of [U(NEt2)(3)][BPh4] and H2C(Ph2PS)(2). Mono-carbenes 2a, 5a, and 9 were used as precursors for the synthesis of Cp and COT derivatives (Cp = C5H5, COT = C8H8). Treatment of 2a with 1 or 2 molar equiv of TlCp gave [Tl{U(Cp)(SCS)}(2)(mu-Cl)(3)] (10) and [U(Cp)(2)(SCS)] (11) in 90% and 79% yield, respectively, whereas [U(Cp*)(2)(SCS)] (12) (Cp* = C5Me5) was obtained only by reaction of [U(Cp*)(2)Cl-2] and Li-2(SCS). Reactions of Sa or 9 with K2COT gave [U(COT)(SCS)(THE)] (13) in 78% and 99% yield, respectively. 2a, [Li(THF)(Et2O)U(SCS)(mu-Cl)(3)](2) (2b), [U(SCS)(2)(py)(2)] center dot 1.5py center dot 0.5THF (3b center dot 1.5py center dot 0.5THF), [U(SCS) {CS(Ph2PS)(2)} (Py)] (4), 7 center dot toluene, [Li(THF)(2)U(SCS)(NEt2)(mu-O)](2) (8), 10 center dot 2toluene, 11, 12, and 13 center dot 0.5pentane were characterized by X-ray diffraction. The crystal data revealed that, in contrast to transition metal complexes, changes in the coordination sphere of the U(IV) center have little influence on the U=C bond. This feature was explained by DFT analysis of analogous U(IV) and Zr(IV) compounds [M(SCS')Cl-2(py)(2)] and [M(SCS')(Cp)(2)] [M = U, Zr; SCS' = C(H2PS)(2)]. Although the 5f orbitals are more radially contracted than the 6d atomic orbitals, the 5f AOs are lower in energy in uranium and can lead to greater angular overlaps in symmetry-constrained systems. As a result, the seven 5f orbitals play a "buffer" role by engaging in covalent interactions with the carbon center to stabilize the nucleophilic carbene lone pairs.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.