Ethylene dimerization catalyzed by mixed phosphine-iminophosphorane nickel(II) complexes: a DFT investigation.

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 asymmetry and the importance of steric and trans effects were elucidated.

Cobalt-catalyzed vinylation of aromatic halides using β-halostyrene: experimental and DFT studies.

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.

Pd(II) and Ni(II) complexes featuring a "phosphasalen" ligand: synthesis and DFT study.

A phosphorus analog of salen ligands featuring iminophosphorane functionalities in place of the imine groups was synthesised in 2 steps from o-diphenylphosphinophenol via 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.

Mechanism of the dehydrogenative silylation of alcohols catalyzed by cationic gold complexes: an experimental and theoretical study.

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.

Double Friedel-Crafts acylation reactions on the same ring of a metallocene: synthesis of a 2,5-diacetylphospharuthenocene.

The synthetic outcome of the Friedel-Crafts acylation of 1',2',3,3',4,4',5'-heptamethylphospharuthenocene reflects the nature of the acylating agent, with alkanoyl anhydride/trifluoromethanesulfonic acid (TfOH) reagents giving monosubstitution at the phospholyl ring, whereas alkanoyl chloride/AlCl(3) gives 2,5-disubstitution. DFT calculations indicate that this unusual double acylation can be facilitated by the intervention of the phosphorus atom at an early stage in the reaction trajectory, with the acyl group being delivered from the phosphorus atom into the ring 2- or 2,5-positions.

Chiral undecagold clusters: synthesis, characterization and investigation in catalysis.

Enantiopure undecagold clusters protected by chiral atropisomeric diphosphine ligands (P^P) have been synthesized by the stoichiometric reduction of the corresponding (P^P)(AuCl)(2) complexes with NaBH(4). The molecular mono-disperse [Au(11)(P^P)(4)Cl(2)]Cl species have been thoroughly characterized using an array of analytical techniques. (31)P NMR experiments suggested the presence of a slow intramolecular ligand exchange process.

Nucleophilic scandium carbene complexes.

Using a geminal dianion as precursor, a nucleophilic scandium carbene complex (2) has been synthesized by salt metathesis on ScCl(3)(THF)(3) in 52% isolated yield. The X-ray structure as well as an NBO analysis points to a double interaction between the carbon and the scandium atoms. Quantification of the electron density donation from the carbon to the metal center, from both σ and π symmetry orbitals, predicts a "nucleophilic carbene" behavior.

White phosphorus and metal nanoparticles: a versatile route to metal phosphide nanoparticles.

P(4) reaction with metal NPs (In, Pb, Zn) provides an easy access to the corresponding metal phosphide NPs in a soft and stoichiometric reaction. Size-influence on the reactivity is investigated in the case of indium.

Easy access to uranium nucleophilic carbene complexes.

Metathesis reactions of UCl(4) with Li(2)C(Ph(2)PS)(2) in Et(2)O only afforded the tris-carbene complex [{Li(OEt(2))}(2)U{=C(Ph(2)PS)(2)}(3)] (1), while the bis- and mono-carbene compounds [U{=C(Ph(2)PS)(2)}(2)(THF)(2)] (2) and [{Li(THF)(2)}(2)U{=C(Ph(2)PS)(2)}Cl(4)] (3) were obtained by treatment of UCl(4) with Li(2)C(Ph(2)PS)(2) in a mixture of THF and toluene. The bis-carbene complex 2 was also obtained either from the comproportionation reaction of 1 and UCl(4) or protonolysis reaction of U(NEt(2))(4) with H(2)C(Ph(2)PS)(2) and was transformed into the mono-carbene complex [U{=C(Ph(2)PS)(2)}Cl(2)(THF)(2)] (4) by further reaction with UCl(4). The utility of these complexes as precursors is illustrated by the synthesis of the biscyclopentadienyl derivative [Cp(2)U{=C(Ph(2)PS)(2)}] (5) by treatment of 3 with TlCp.

Interplay between hydrido/dihydrogen and amine/amido ligands in ruthenium-catalyzed transfer hydrogenation of ketones.

This work describes the synthesis of three key intermediates of Noyori-type catalytic systems that are active precatalysts for the transfer hydrogenation of acetophenone. Isolation of the cationic chloro(dihydrogen) complex [RuCl(H(2))(H(2)NNPP)(PCy(3))][BArf(4)] provides a facile synthetic route to the corresponding cationic and neutral hydrido complexes, and the series highlights the links between hydride/dihydrogen and amine/amido ligands in neutral and cationic species.

Phosphorus stabilized carbene complexes: bisphosphonate dianion synthesis, reactivity and DFT studies of O~C~O zirconium(IV) complexes.

The reactivity of the geminal dianion of tetraisopropyl methylenediphosphonate, 3, with [ZrCl4(THF)2] affords a trinuclear structure 5 in which an unprecedented triscarbene-Zr dianionic fragment is found. The overall trinuclear arrangement is assembled by PO bridging moieties. The X-ray crystal structure of 5 is presented.

First neodymium(III) alkyl-carbene complex based on bis(iminophosphoranyl) ligands.

Serendipitous deprotonation of bis(iminophosphoranyl)methanide Nd(III) complexes afforded the first alkyl-carbene neodymium complex. Due to the presence of structurally similar methanide and methandiide fragments, this complex features, as evidenced by X-ray crystallographic analysis, Nd-C single and multiple bonds.

How the choice of a computational model could rule the chemical interpretation: the Ni(II) catalyzed ethylene dimerization as a case study.

In this article, we present a critical study of the theoretical protocol used for the determination of the nickel(II) catalyzed ethylene dimerization mechanism, considered as a representative example of the various problems related to the modeling a catalytic cycle. The choice of an appropriate computational procedure is indeed crucial for the validity of the conclusions that will be drawn from the computational process. The influence of the exchange-correlation functional on energetic profiles and geometries, the role of the basis set describing the metal atom, as well as the importance of the chosen molecular model, have been thus examined in details.

Cationic dimetallic gold hydride complex stabilized by a xantphos-phosphole ligand: synthesis, X-ray crystal structure, and density functional theory study.

The bis-2,5-diphenylphosphole xantphos ligand (XDPP) 1 reacts with the [AuCl(tht)] complex to afford the monocoordinated [Au(XDPP)Cl] 2 and the dicoordinated chelate species [Au(XDPP)Cl] 3. Addition of AgOTf on this mixture, at room temperature, affords the cationic [Au(XDPP)][OTf] complex 4 which was fully characterized. An X-ray crystal structure analysis confirms the bent structure of this 14 VE [ML(2)](+) complex.

PCNCP ligands in the chromium-catalyzed oligomerization of ethylene: tri- versus tetramerization.

Chromium(III) complexes bearing R'N(CH2PR2)2 (PCNCP) ligands have been prepared. Upon activation with methylaluminoxane, these complexes proved to be effective in the selective tri- and tetramerization of ethylene. The formation of either 1-hexene or 1-octene was found to be highly dependent on the steric bulk of the substituents R on the phosphine moieties.

Bonding mode of a new bis-phosphine-borane alkyl ligand to a Rh(I) species.

The stoichiometric reaction of [Rh(COD)Cl](2) with the anion resulting from the deprotonation of dppm(BH(3))(2) yielded a new alkyl Rh(I) complex; the coordination modes of the BH(3) groups are discussed on the basis of X-ray data, variable temperature multinuclear NMR experiments and DFT studies.

Coordination of tetradentate X2N2 (X = P, S, O) ligands to iron(II) metal center and catalytic application in the transfer hydrogenation of ketones.

A series of mixed tetradentate ligands associating two iminophosphorane moieties with two phosphino, thiophosphino, or phosphine oxide groups (labelled 2, 3, and 4 respectively) have been prepared from the corresponding aminophosphonium derivatives. Their coordination to the iron dichloride metal fragment was achieved using the [FeCl(2)(THF)(1.5)] precursor leading to [(P(2)N(2))FeCl(2)] (5), [(S(2)N(2))FeCl(2)] (6), and [(O(2)N(2))FeCl(2)] (7).

Cobalt-catalyzed formation of symmetrical biaryls and its mechanism.

Effective devotion: An efficient cobalt-catalyzed method devoted to the formation of symmetrical biaryls is described avoiding the preparation of organometallic reagents. Various aromatic halides functionalized by a variety of reactive group reagents are employed. Preliminary DFT calculations have shown that the involvement of a Co(I)/Co(III) couple is realistic at least in the case of 1,3-diazadienes as ligands (FG = functional group).

The U=C double bond: synthesis and study of uranium nucleophilic carbene complexes.

Treatment of U(BH(4))(4) with 1 or 3 equiv of Li(2)(SCS) x 1.5 Et(2)O, 1, afforded the actinide carbene complexes U(mu-SCS)(3)[U(BH(4))(3)](2) (4) and U(mu-SCS)(3)[Li(Et(2)O)](2) (6), respectively [SCS = (Ph(2)P = S)(2)C]. In THF, complex 4 was transformed into the mononuclear derivative (SCS)U(BH(4))(2)(THF)(2) (5).

1-phosphabarrelene complexes of palladium and their use in Suzuki-Miyaura coupling reactions.

A bulky 1-phosphabarrelene, , was obtained from the reaction of a phosphinine with benzyne; two palladium complexes of were successfully employed in the Suzuki-Miyaura coupling of several aryl chlorides with phenylboronic acid at a relatively low catalyst loading, and activated aryl chlorides were coupled at room temperature in the absence of strong bases.

Why platinum catalysts involving ligands with large bite angle are so efficient in the allylation of amines: design of a highly active catalyst and comprehensive experimental and DFT study.

The platinum-catalyzed allylation of amines with allyl alcohols was studied experimentally and theoretically. The complexes [Pt(eta(3)-allyl)(dppe)]OTf (2) and [Pt(eta(3)-allyl)(DPP-Xantphos)]PF(6) (5) were synthesized and structurally characterized, and their reactivity toward amines was explored. The bicyclic aminopropyl complex [Pt(CH(2)CH(2)CH(2)NHBn-kappa-C,N)(dppe)]OTf (3) was obtained from the reaction of complex 2 with an excess of benzylamine, and this complex was shown to be a deactivated form of catalyst 2.

Bonding mode of a bifunctional P approximately Si-H ligand in the ruthenium complex "Ru(PPh2CH2OSiMe2H)3".

The phosphinosilane compound PPh 2CH 2OSiMe 2H is potentially a bifunctional P approximately Si-H ligand. By treatment with the Ru (II) precursor RuH 2(H 2) 2(PCy 3) 2, the complex Ru(PPh 2CH 2OSiMe 2H) 3 ( 2), resulting from the coordination of three ligands and the displacement of two PCy 3 and two dihydrogen ligands, was formed. The different bonding modes for each of the three bifunctional P approximately Si-H ligands are discussed on the basis of multinuclear NMR, X-ray diffraction, and density functional theory studies.

White phosphorus as single source of "P" in the synthesis of nickel phosphide.

White phosphorus, P4, was reacted in a stoichiometric manner with Ni(0) complexes or particles to produce nanoparticles of nickel phosphide.