956 research outputs found

    A Homologous Series of Cobalt, Rhodium, and Iridium Metalloradicals

    Get PDF
    We herein present a series of d7 trimethylphosphine complexes of group 9 metals that are chelated by the tripodal tetradentate tris(phosphino)silyl ligand [SiP^(iPr)_3]H ([SiP^(iPr)_3] = (2_(-i)Pr_2PC_6H_4)_3Si^–). Both electron paramagnetic resonance (EPR) simulations and density functional theory (DFT) calculations indicate largely metalloradical character. These complexes provide a rare opportunity to compare the properties between the low-valent metalloradicals of the second- and third-row transition metals with the corresponding first-row analogues

    N_2 Functionalization at Iron Metallaboratranes

    Get PDF
    The reactivity of the anionic dinitrogen complex [(TPB)Fe(N_2)]^− (TPB = tris[2-(diisopropylphosphino)phenyl]borane) toward silicon electrophiles has been examined. [(TPB)Fe(N_2)]^− reacts with trimethylsilyl chloride to yield the silyldiazenido complex (TPB)Fe(NNSiMe_3), which is reduced by Na/Hg in THF to yield the corresponding sodium-bound anion [(TPB)Fe(NNSiMe_3)]Na(THF). The use of 1,2-bis(chlorodimethylsilyl)ethane in the presence of excess Na/Hg results in the disilylation of the bound N_2 molecule to yield the disilylhydrazido(2−) complex (TPB)Fe≡NR (R = 2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentyl). One of the phosphine arms of TPB in (TPB)Fe≡NR can be substituted by CO or ^tBuNC to yield crystalline adducts (TPB)(L)Fe≡NR (L = CO, ^tBuNC). The N–N bond in (TPB)(^tBuNC)Fe≡NR is cleaved upon standing at room temperature to yield a phosphoraniminato/disilylamido iron(II) complex. The flexibility of the Fe–B linkage is thought to play a key role in these transformations of Fe-bound dinitrogen

    Reversible H_2 Addition across a Nickel−Borane Unit as a Promising Strategy for Catalysis

    Get PDF
    We report the synthesis and characterization of a series of nickel complexes of the chelating diphosphine-borane ligands ArB(o-Ph_2PC_6H_4)_2 ([^(Ar)DPB^(Ph)]; Ar = Ph, Mes). The [^(Ar)DPB^(Ph)] framework supports pseudo-tetrahedral nickel complexes featuring η^2-B,C coordination from the ligand backbone. For the B-phenyl derivative, the THF adduct [^(Ph)DPB^(Ph)]Ni(THF) has been characterized by X-ray diffraction and features a very short interaction between nickel and the η^2-B,C ligand. For the B-mesityl derivative, the reduced nickel complex [^(Mes)DPB^(Ph)]Ni is isolated as a pseudo-three-coordinate “naked” species that undergoes reversible, nearly thermoneutral oxidative addition of dihydrogen to give a borohydrido-hydride complex of nickel(II) which has been characterized in solution by multinuclear NMR. Furthermore, [^(Mes)DPB^(Ph)]Ni is an efficient catalyst for the hydrogenation of olefin substrates under mild conditions

    E−H Bond Activation Reactions (E = H, C, Si, Ge) at Ruthenium: Terminal Phosphides, Silylenes, and Germylenes

    Get PDF
    The placement of a strongly trans-influencing ligand on a ruthenium center opposite an anchoring silyl group of the tetradentate tripodal tris(phosphino)silyl ligand, [SiP^(Ph)_3]^− ([SiP^(Ph)_3]^− = tris(2-(diphenylphosphino)phenyl)silyl), has been explored. Installation of alkyl or terminal phosphide ligands trans to the anchoring silyl group affords the complexes [SiPPh3]RuR (R = Me (2), CH_2Ph (4), PPh_2 (5), P^iPr_2 (6)). Complexes 2, 4, and 5 are thermally unstable. Complexes 2 and 4 decay to the cyclometalated complex [SiP^(Ph)_2P′^(Ph)]Ru (3), whereas complex 5 decays to the cyclometalated phosphine adduct [SiP^(Ph)_2P′^(Ph)]Ru(PHPh_2) (7). Complex 3 is found to effect E−H (E = H, C, Si, Ge) bond activation of substrates such as secondary silanes and germanes to yield the structurally unusual silylene complexes [SiP^(Ph)_3]Ru(H)(SiRR′) (R = R′ = Ph (10a), R = Ph R′ = Me (10b)) and the germylene complex [SiP^(Ph)_3]Ru(H)(GeR_2) (R = Ph) (11) via double E−H activation transformations. Both theory and experiments suggest electrophilic character at the silylene moiety. Reaction of 3 with catecholborane, in contrast to silanes and germanes, results in insertion of the B−H unit into the M−C bond of the cyclometalated species to yield the borate complex [SiP^(Ph)_2P^(Ph)-B(cat)]Ru(μ-H) (14). Complex 3 also reacts with bis(catecholato)diboron to yield a similar complex, [SiP^(Ph)_2P^(C6H3B(cat))-B(cat)]Ru(μ-H) (15), with selective borylation of an ortho C−H bond

    Ligand design for site-selective installation of Pd and Pt centers to generate homo- and heteropolymetallic motifs

    Get PDF
    The modular synthesis of a series of nitrogen-rich polydentate ligands that feature a common pincer-type framework is reported. These ligands allow for site-selective installation of palladium and platinum to give rise to bi- and trimetallic complexes that have d^(8)–d^(8) interactions

    A terminal molybdenum carbide prepared by methylidyne deprotonation

    Get PDF
    The carbide anion [CMo{N(R)Ar}_3]– [R = C(CD_3)_2CH_3, Ar = C_6H_3Me_2-3,5], is obtained by deprotonation of the corresponding methylidyne compound, [HCMo{N(R)Ar}_3], and is characterized by X-ray diffraction as its {K(benzo-15-crown-5)_2}+ salt, thereby providing precedent for the carbon atom as a terminal substituent in transition-metal chemistry

    Dinitrogen Complexes of Sulfur-Ligated Iron

    Get PDF
    We report a unique class of dinitrogen complexes of iron featuring sulfur donors in the ancillary ligand. The ligands utilized are related to the recently studied tris(phosphino)silyl ligands (2-R_2PC_6H_4)_3Si (R = Ph, iPr) but have one or two phosphine arms replaced with thioether donors. Depending on the number of phosphine arms replaced, both mononuclear and dinuclear iron complexes with dinitrogen are accessible. These complexes contribute to a desirable class of model complexes that possess both dinitrogen and sulfur ligands in the immediate iron coordination sphere

    Complexes of iron and cobalt with new tripodal amido-polyphosphine hybrid ligands

    Get PDF
    Divalent complexes of iron and cobalt with new, monoanionic tripodal amido-polyphosphine ligands have been thoroughly characterized, and XRD analysis reveals geometries that are distinct for this class of ligand
    corecore