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A family of low-valent molybdenum complexes supported by the pincer ligand PNMeP (PNMeP = MeN(CH2CH2PPh2)2) was prepared and characterized, including (PNMeP)Mo(C2H4)2, which contains an agostic interaction between the metal and the N-methyl substituent. This β-agostic C–H bond was cleaved by molybdenum and produced a cyclometalated molybdenum formate complex, (κ4-PNMeP)Mo(C2H4)(κ2-O2CH), upon exposure to CO2. This species serves as a promotor of CO2 hydrogenation to formate under basic conditions, a rare transformation for group VI metals. The performance of the precatalyst was enhanced with the addition of Lewis acid salts.

A series of zerovalent molybdenum complexes bearing triphosphine ligands, [Ar2PCH2CH2]2PPh, have been synthesized and evaluated for reductive functionalization of CO2 with ethylene. The ability to form dimeric triphosphine molybdenum(II) acrylate hydride species from CO2-ethylene coupling was found to be highly sensitive to steric encumbrance on the phosphine aryl substituents. Trapping of triphosphine molybdenum(II) acrylate hydride species using triphenylphosphine afforded isolable monomeric CO2 functionalization products with all ancillary ligands studied. Kinetic analysis of the acrylate formation reaction revealed a first-order dependence on molybdenum, but no influence from CO2 pressure or the triphenylphosphine trap. Systematic attenuation of steric and electronic features of the triphosphine ligands showed a strong CO2 functionalization rate influence for ligand size with [(3,5-tBu-C6H3)2PCH2CH2]2PPh coupling nearly four times slower than with [(3,5-Me-C6H3)2PCH2CH2]2PPh. A considerably milder ele...

The molybdenum tetrahydride species (Triphos)MoH4PPh3 (Triphos = PhP(CH2CH2PPh2)2) generated from sodium triethylborohydride addition to (Triphos)MoCl3 was found to promote CO2 functionalization to afford acrylate, propionate, and formate species. The formation of (Triphos)MoH4PPh3 occurs via a (Triphos)Mo(H)Cl(PPh3) intermediate followed by dismutation of an unobserved six-coordinate molybdenum(II) dihydride complex. Addition of dihydrogen to the dismuation product mixture affords a nearly quantitative yield of (Triphos)MoH4PPh3. The molybdenum tetrahydride species facilitates CO2 insertion into a metal hydride to produce a formate complex, (Triphos)Mo(H)(κ2-CHO2)(PPh3), with an observed rate constant of [2.9(2)] × 10–4 s–1 (25 °C), which is independent of CO2 pressure. Selective formation of acrylate and propionate carbon dioxide–ethylene coupling products, (Triphos)Mo(H)(κ2-C3H3O2)(PPh3) and (Triphos)Mo(H)(κ2-C3H5O2)(PPh3), was achieved by sequential addition of olefin and heterocumulene to (Triphos)Mo...

The Lewis acid tris(pentafluorophenyl)borane was found to rapidly promote ring-opening β-hydride elimination in a 1,1′-bis(diphenylphosphino)ferrocene (dppf) nickelalactone complex under ambient conditions. The thermodynamic product of nickelalactone ring-opening was characterized as (dppf)Ni(CH(CH3)CO2BArf3), the result of β-hydride elimination and subsequent 2,1-insertion from a transient nickel(II) acrylate hydride intermediate. Treatment of (dppf)Ni(CH(CH3)CO2BArf3) with a nitrogen-containing base afforded a diphosphine nickel(0) η2-acryl borate adduct. Formation of the diphosphine nickel(0) η2-acryl borate adduct completes a net conversion of nickelalactone to acrylate species, a significant obstacle to catalytic acrylate production from CO2 and ethylene. Displacement of the η2-acrylate fragment from the nickel center was accomplished by addition of ethylene to yield a free acrylate salt and (dppf)Ni(CH2═CH2).

The cobalt(III) dimethyl halide complexes cis,mer-(PMe3)3Co(CH3)2X (X = Cl, I) were found to undergo a degenerate cobalt-to-cobalt transfer of the methyl ligands during isotopic labeling experiment...

Lithium, sodium, and potassium enolates reacted with bisaminoboron halides to give bisaminoboron enolates 1a−5c. Specifically, the potassium enolate of tert-butyl methyl ketone reacted with bis(dii...

A cobalt(I) methyl species, (PMe3)4CoCH3, was found to promote C–CN bond oxidative addition of acetonitrile at ambient temperature. The isolated product of acetonitrile activation, cis,mer-(PMe3)3Co(CH3)2CN, was characterized by NMR, IR, and single-crystal X-ray diffraction studies and presents a higher valent metal in comparison to those previously observed for base-metal-mediated nitrile activations. A short-lived reaction intermediate was detected during nitrile cleavage and identified as fac-(PMe3)3Co(CH3)2CN, the kinetic product of C–CN oxidative addition. Conversion of the kinetic product to cis,mer-(PMe3)3Co(CH3)2CN proceeds with a rate constant of [1.0(1)] × 10–3 s–1 at 27 °C.

Successful application of physically separated internal references for determination of formula weights of compounds in solution by 31P DOSY NMR is described. The solution-state structures of a variety of manganese compounds were investigated.

Addition of 1 equiv of N,N,2,2-tetramethylpropanediamine (4) to 1 equiv of either lithium dibenzylamide (1) or lithium 2,2,6,6-tetramethylpiperidide (2) results in the exclusive formation of the pr...

L'addition de nucleophiles (Nu) donneurs de P et N au noyau cycloheptatriene dans (C 7 H 8 )Mn(CO) 2 L + (L=CO, PPh 3 ) donne (exo-N 4 C 7 H 8 )Mn(CO) 2 L + . Etude RX de [(exo-PPh 3 C 7 H 8 )Mn(CO) 3 ]BF 4

(C 6 H 6 Ph)Mn(CO) 3 et [(C 6 H 6 Ph•PBu 3 )Mn(CO) 2 NO]PF 6 cristallisent dans le systeme monoclinique, groupe d'espace P2 1 /c et leur structure est affinee respectivement jusqu'a R=0,029 et R=0,049 [(C 6 H 6 Me)Mn(CO) 2 NO]PF 6 cristallise dans P2 1 /n avec R=0,032