Low-coordinate bis-phosphine and monophosphine Ni(0) complexes: synthesis and reactivity in C-S cross-coupling.

Preformed Ni(0) complexes are rarely used as precatalysts in cross-coupling reactions, although they can incorporate catalytically active nickel directly into the reaction. In this work, we focus on the preparation and the catalytic application of low-coordinate Ni(0) complexes supported by bulky monophosphine ligands in C-S cross-coupling reactions. We have prepared two families of Ni(0) complexes, bis-phosphine aducts of the type [Ni(PRAr')] (Ar' = -terphenyl group) and monophosphine derivatives of the type [Ni(PRAr')(DVDS)] (DVDS = divinyltetramethyldisiloxane).

Ligand Postsynthetic Functionalization with Fluorinated Boranes and Implications in Hydrogenation Catalysis.

The incorporation of boron functionalities into transition-metal catalysts has become a promising strategy to improve catalytic performance, although their synthesis typically entails the preparation of sophisticated bifunctional ligands. We report here the facile and direct postsynthetic functionalization of rhodium(I) compound [(η-CH)Rh(PPh)] () by treatment with perfluorinated boranes. Borane addition to results in an unusual C(sp)-H hydride migration from the indenyl ligand to the metal with the concomitant formation of a C-B bond.

Important Role of NH-Carbazole in Aryl Amination Reactions Catalyzed by 2-Aminobiphenyl Palladacycles.

2-Aminobiphenyl palladacycles are among the most successful precatalysts for Pd-catalyzed cross-coupling reactions, including aryl amination. However, the role of NH-carbazole, a byproduct of precatalyst activation, remains poorly understood. Herein, the mechanism of the aryl amination reactions catalyzed by a cationic 2-aminobiphenyl palladacycle supported by a terphenyl phosphine ligand, PCypAr (Cyp = cyclopentyl; Ar = 2,6-bis(2,6-dimethylphenyl)phenyl), , has been thoroughly investigated.

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Polarized Au(I)/Rh(I) bimetallic pairs cooperatively trigger ligand non-innocence and bond activation.

The combination of molecular metallic fragments of contrasting Lewis character offers many possibilities for cooperative bond activation and for the disclosure of unusual reactivity. Here we provide a systematic investigation on the partnership of Lewis basic Rh(I) compounds of type [(η-L)Rh(PR)] (η-L = (CMe) or (CH)) with highly congested Lewis acidic Au(I) species. For the cyclopentadienyl Rh(I) compounds, we demonstrate the non-innocent role of the typically robust (CMe) ligand through migration of a hydride to the Rh site and provide evidence for the direct implication of the gold fragment in this unusual bimetallic ligand activation event.

LPdCl(amine) complexes supported by terphenyl phosphanes: applications in aryl amination reactions.

Despite the excellent catalytic properties display by NHC-Pd-PEPPSI complexes in cross-coupling, phosphane analogs have been barely screened. In this work, we report the synthesis and characterization of a series of LPdCl(amine) complexes bearing dialkylterphenyl phosphanes (PRAr') and pyridine or morpholine ligands. The novel compounds have been tested as precatalysts in aryl amination reactions.

Electrophilic activation of alkynes promoted by a cationic alkylidene complex of Pt(II).

Pt(II) alkylidene 1a has been reacted with terminal alkynes to afford ylide complexes 3a-d, resulting from electrophilic activation of the CC bond and its insertion into the platinacyclic fragment of 1a that contains the carbene functionality. DFT calculations indicate that the observed regioselectivity is determined by the nucleophilic attack of the alkyne to the alkylidene carbon.

Reactivity of [Pt(P Bu)] with Zinc(I/II) Compounds: Bimetallic Adducts, Zn-Zn Bond Cleavage, and Cooperative Reactivity.

Metal-only Lewis pairs (MOLPs) based on zinc electrophiles are particularly interesting due to their relevance to Negishi cross-coupling reactions. Zinc-based ligands in bimetallic complexes also render unique reactivity to the transition metals at which they are bound. Here we explore the use of sterically hindered [Pt(P Bu)] () to access Pt/Zn bimetallic complexes.

Ni(II) Precatalysts Enable Thioetherification of (Hetero)Aryl Halides and Tosylates and Tandem C-S/C-N Couplings.

Ni-catalyzed C-S cross-coupling reactions have received less attention compared with other C-heteroatom couplings. Most reported examples comprise the thioetherification of most reactive aryl iodides with aromatic thiols. The use of C-O electrophiles in this context is almost uncharted.

Coordination of LiH Molecules to Mo≣Mo Bonds: Experimental and Computational Studies on MoLiH, MoLiH, and MoLiH Clusters.

The reactions of LiAlH as the source of LiH with complexes that contain (H)Mo≣Mo and (H)Mo≣Mo(H) cores stabilized by the coordination of bulky Ad ligands result in the respective coordination of one and two molecules of (thf)LiH, with the generation of complexes exhibiting one and two HLi(thf)H ligands extending across the Mo≣Mo bond (Ad = HC(NDipp); Dipp = 2,6-PrCH; thf = tetrahydrofuran, CHO). A theoretical study reveals the formation of Mo-H-Li three-center-two-electron bonds, supplemented by the coordination of the Mo≣Mo bond to the Li ion. Attempts to construct a [Mo{HLi(thf)H}(Ad)] molecular architecture led to spontaneous trimerization and the formation of a chiral, hydride-rich MoLiH supramolecular organization that is robust enough to withstand the substitution of lithium-solvating molecules of tetrahydrofuran by pyridine or 4-dimethylaminopyridine.

Zero-valent ML complexes of group 10 metals supported by terphenyl phosphanes.

Bulky terphenyl phosphane ligands PMeAr' (Ar' = terphenyl group) facilitate the isolation of zero-valent bis-phosphane complexes of nickel, palladium and platinum. The former show coordination numbers greater than two in the solid state due to the existence of Ni-C interactions with the terphenyl fragment.

Experimental and Computational Studies on Quadruply Bonded Dimolybdenum Complexes with Terminal and Bridging Hydride Ligands.

This contribution focuses on complex [Mo (H) (μ-Ad ) ] (1) and tetrahydrofuran and pyridine adducts [Mo (H) (μ-Ad ) (L) ] (1⋅thf and 1⋅py), which contain a trans-(H)Mo≣Mo(H) core (Ad =HC(NDipp ) ; Dipp=2,6-iPr C H ). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo H unit of 1, with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe , can bind to 1, causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond (2⋅PMe ).

Tuning Activity and Selectivity during Alkyne Activation by Gold(I)/Platinum(0) Frustrated Lewis Pairs.

Introducing transition metals into frustrated Lewis pair systems has attracted considerable attention in recent years. Here we report a selection of three metal-only frustrated systems based on Au(I)/Pt(0) combinations and their reactivity toward alkynes. We have inspected the activation of acetylene and phenylacetylene.

Dinuclear Cu(I) Halides with Terphenyl Phosphines: Synthesis, Photophysical Studies, and Catalytic Applications in CuAAC Reactions.

Several dinuclear terphenyl phosphine copper(I) halide complexes of composition [CuX(PRAr')] (X = Cl, Br, I; R = hydrocarbyl, Ar' = 2,6-diarylterphenyl radical), -, have been isolated from the reaction of CuX with 1 equiv of the phosphine ligand. Most of them have been characterized by X-ray diffraction studies in the solid state, thus allowing comparative discussions of different structural parameters, namely, Cu···Cu and Cu···Aryl separations, conformations adopted by coordinated phosphines, and planarity of the CuX cores. Centrosymmetric complexes [CuI(PMeAr)], , and [CuI(PEtAr)], , despite their similar structures, show very distinct photoluminescence (PL) in powder form at room temperature.

Evidence for Genuine Bimetallic Frustrated Lewis Pair Activation of Dihydrogen with Gold(I)/Platinum(0) Systems.

Invited for the cover of this issue is the group of Joaquín López-Serrano and Jesús Campos at the Consejo Superior de Investigaciones Científicas and the University of Sevilla. The image depicts the importance of balancing the degree of frustration/interaction in the splitting of H by Au /Pt . Read the full text of the article at 10.

A Versatile Approach to Access Trimetallic Complexes Based on Trisphosphinite Ligands.

A straightforward method for the preparation of trisphosphinite ligands in one step, using only commercially available reagents (1,1,1-tris(4-hydroxyphenyl)ethane and chlorophosphines) is described. We have made use of this approach to prepare a small family of four trisphosphinite ligands of formula [CHC{(CHOR)], where R stands for Ph (), Xyl (, Xyl = 2,6-Me-CH), Pr (), and Cy (). These polyfunctional phosphinites allowed us to investigate their coordination chemistry towards a range of late transition metal precursors.

Evidence for Genuine Bimetallic Frustrated Lewis Pair Activation of Dihydrogen with Gold(I)/Platinum(0) Systems.

A joint experimental/computational effort to elucidate the mechanism of dihydrogen activation by a gold(I)/platinum(0) metal-only frustrated Lewis pair (FLP) is described herein. The drastic effects on H activation derived from subtle ligand modifications have also been investigated. The importance of the balance between bimetallic adduct formation and complete frustration has been interrogated, providing for the first time evidence for genuine metal-only FLP reactivity in solution.

Dialkylterphenyl Phosphine-Based Palladium Precatalysts for Efficient Aryl Amination of N-Nucleophiles.

A series of 2-aminobiphenyl palladacycles supported by dialkylterphenyl phosphines, PR Ar' (R=Me, Et, iPr, Cyp (cyclopentyl), Ar'=Ar , Ar , Dipp (2,6-C6H3-(2,6-C6H3-(CHMe2)2)2), Xyl=xylyl) have been prepared and structurally characterized. Neutral palladacycles were obtained with less bulky terphenyl phosphines (i.e.

Palladium-mediated intramolecular dearomatization of ligated dialkylterphenyl phosphines.

Aryl-Pd(ii) chlorides stabilized by dialkylterphenyl phosphine ligands undergo a thermal isomerization process, leading to the formation of allyl-Pd(ii)-chloride species. The transformation involves the intramolecular functionalization of a C-H bond of the terphenyl group mediated by the Pd(ii) center.

Cooperative activation of X-H (X = H, C, O, N) bonds by a Pt(0)/Ag(i) metal-only Lewis pair.

Metal-only Lewis pairs made of Pt(0)/Ag(i) combinations have been previously reported, but their cooperative reactivity remains unexplored. Here we demonstrate that these systems are capable of synergistically activating a wide variety of X-H (X = H, C, O, N) bonds, including those in dihydrogen, alkynes, water and ammonia.

Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines.

The experimental and computational characterization of a series of dialkylterphenyl phosphines, PR Ar' is described. The new P-donors comprise five compounds of general formula PR Ar (R=Me, Et, iPr, c-C H and c-C H ); Ar = 2,6-C H -(3,5-C H -(CMe ) ) ), and another five PR Ar' phosphines containing the bulky alkyl groups iPr, c-C H or c-C H , in combination with Ar'=Ar , Ar , or Ar (L1-L10). Steric and electronic parameters have been determined computationally and from IR and X-ray data obtained for the phosphines and for some derivatives, including tricarbonyl and dicarbonyl nickel complexes, Ni(CO) (PR Ar') and Ni(CO) (PR Ar').

A Cationic Unsaturated Platinum(II) Complex that Promotes the Tautomerization of Acetylene to Vinylidene.

Complex [PtMe (PMe ArDipp2 )] (1), which contains a tethered terphenyl phosphine (ArDipp2 =2,6-(2,6- Pr C H ) C H ), reacts with [H(Et O) ]BAr (BAr =B[3,5-(CF ) C H ] ) to give the solvent (S) complex [PtMe(S)(PMe ArDipp2 )] (2⋅S). Although the solvent molecule is easily displaced by a Lewis base (e.g.

An Unsaturated Four-Coordinate Dimethyl Dimolybdenum Complex with a Molybdenum-Molybdenum Quadruple Bond.

We describe the synthesis and the molecular and electronic structures of the complex [Mo Me {μ-HC(NDipp) } ] (2; Dipp=2,6-iPr C H ), which contains a dimetallic core with an Mo-Mo quadruple bond and features uncommon four-coordinate geometry and has a fourteen-electron count for each molybdenum atom. The coordination polyhedron approaches a square pyramid, with one of the molybdenum atoms nearly co-planar with the basal square plane, in which the trans coordination position with respect to the Mo-Me bond is vacant. The other three sites are occupied by two trans nitrogen atoms of different amidinate ligands and the methyl group.

Platinum(0) olefin complexes of a bulky terphenylphosphine ligand. Synthetic, structural and reactivity studies.

A novel terphenylphosphine PMe2Ar(Dipp2) () (Dipp = 2,6-(i)Pr2C6H3) forms stable Pt(0) complexes with ethene and 3,3-dimethylbut-1-ene that behave as sources of the reactive Pt(PMe2Ar(Dipp2)) fragment. The complexes are efficient catalysts for the selective hydrosilylation of terminal alkynes.