Ynone Co-Coordination at a Nickel Borane Complex: An Assessment of Secondary Coordination Sphere Effects.

Secondary coordination sphere ligand effects can be used to direct or organize small molecule substrates at a metal center. Herein, we assess the bifunctional ambiphilic diphosphine, tri--butylboranyldiphosphinoethane (tbbpe) and its ability to influence stereoselective substrate coordination, while appended to nickel. This report takes a synthetic/computational approach to test the impacts and limitations associated with ligand-directed substrate coordination using [Ni(tbbpe)(η:η-COD)] (COD = 1,5-cyclooctadiene) and ynones (alkynes having an α-carbonyl group at the propargylic position) as model substrates.

Reactions of nickel boranyl compounds with pnictogen-carbon triple bonds.

The catalytic conversion of unsaturated small molecules such as nitriles into reduced products is of interest for the production of fine chemicals. In this vein, metal-ligand cooperativity has been leveraged to promote such reactivity, often conferring stability to bound substrate - a balancing act that may offer activation at the cost of turnover efficiency. This report describes the reactivity of a [(diphosphine)Ni] compound with pnictogen carbon triple bonds (R-C[triple bond, length as m-dash]E; E = N, P), where the diphosphine contains two pendant borane groups.

Bis(1-bora-4-phosphorinane) ring closure at Cp*M (M = Fe, Co) complexes.

Bis(1-bora-4-phosphorinane) metal complexes have been synthesized using a Cp*M-protecting (M = FeCl, Co, Cp* = CMe) strategy and structurally authenticated by NMR spectroscopy and single crystal X-ray diffraction. Synthesis of these scaffolds is highly sensitive to the identity of vinylphosphine precursor. This approach provides a new method for the generation of saturated ,-containing main-group ring systems.

Competitive gold/nickel transmetalation.

Transmetalation is a key method for the construction of element-element bonds. Here, we disclose the reactivity of [Ni(Ar)(I)(diphosphine)] compounds with arylgold(I) transmetalating agents, which is directly relevant to cross-coupling catalysis. Both aryl-for-iodide and unexpected aryl-for-aryl transmetalation are witnessed.

Lewis Acid-Promoted Oxidative Addition at a [Ni (diphosphine) ] Complex: The Critical Role of a Secondary Coordination Sphere.

Oxidative addition represents a critical elementary step in myriad catalytic transformations. Here, the importance of thoughtful ligand design cannot be overstated. In this work, we report the intermolecular activation of iodobenzene (PhI) at a coordinatively saturated 18-electron [Ni (diphosphine) ] complex bearing a Lewis acidic secondary coordination sphere.

Preparation of a borane-appended Co(III) hydride: evidence for metal-ligand cooperativity in O-H bond activation.

Cobalt hydrides are known to mediate a number of important chemical transformations including proton (H), hydride (H), and hydrogen-atom (H˙) transfer. Central to the tunability of such frameworks is judicious ligand design, which offers the flexibility to alter fundamental properties relevant to reactivity. Herein, we report the preparation of one such cobalt(III) hydride: [Cp*Co(PB)(H)]BPh (Cp* = CMe, PB = 1,2-bis(di(3-dicyclohexylborane)propylphosphino)ethane) that is encircled by a boron-based Lewis-acidic secondary coordination sphere.