Imido silyl complexes of molybdenum: synthesis, structure, and unusual H2/silane exchange

Reaction of complex (ArN)Mo(H)(Cl)(PMe3)3 (1) with BPh3 and silane H3SiPh affords a new silyl complex (ArN)Mo(SiH2Ph)(Cl)(PMe3)2 (3) that catalyses facile H–H/Si–H exchange. EXSY experiments suggest that this exchange does not involve the classical pathways such as oxidative addition of hydrogen or silane to the complex or σ-bond metathesis. It is suggested that the exchange may occur in an FLP cage comprised by the complex and the silane.

Mechanism of the Iridium-Catalyzed Silylation of Aromatic C–H Bonds

<p>The iridium-catalyzed silylation of aromatic C–H bonds has become a synthetically valuable reaction because it forms aryl silanes with high sterically derived regioselectivity with silane reagents that are produced and consumed on large scales. Many groups, including our own, have reported iridium complexes of phenanthroline or bipyridine ligands as catalysts for this reaction. Yet, little is known about the mechanism by which the iridium-catalyzed silylation of arenes occurs. Indeed, no iridium-silyl complexes have been prepared that react with C-H bonds to form C-Si bonds in a fashion that is chemically and kinetically competent to be part of the catalytic cycle. </p><p><br></p> <p>In this manuscript, we report the synthesis and reactivity of iridium-silyl compelexes of the 2,9-Me₂Phen ligand that generates the most active known catalyst for the silylation of aromatic C-H bonds. We show by experiment and computation that the most stable and most reactive silyl complex of this ligand contains two silyl and one hydride ligands and by kinetic analysis of the catalytic reaction determine the rate-limiting step for arenes with varying electronic properties. Computational studies indicate that the steric encumberance of the phenanthroline ligand controls the number of silyl ligands bound to iridium and that the difference in the number of silyl ligands leads to large differences to the rates of the reaction. These studies provide insight into the origins of the high activity of the catalyst containing the 2,9-Me₂Phen ligand.</p>

Mechanism of the Iridium-Catalyzed Silylation of Aromatic C–H Bonds

<p>The iridium-catalyzed silylation of aromatic C–H bonds has become a synthetically valuable reaction because it forms aryl silanes with high sterically derived regioselectivity with silane reagents that are produced and consumed on large scales. Many groups, including our own, have reported iridium complexes of phenanthroline or bipyridine ligands as catalysts for this reaction. Yet, little is known about the mechanism by which the iridium-catalyzed silylation of arenes occurs. Indeed, no iridium-silyl complexes have been prepared that react with C-H bonds to form C-Si bonds in a fashion that is chemically and kinetically competent to be part of the catalytic cycle. </p><p><br></p> <p>In this manuscript, we report the synthesis and reactivity of iridium-silyl compelexes of the 2,9-Me₂Phen ligand that generates the most active known catalyst for the silylation of aromatic C-H bonds. We show by experiment and computation that the most stable and most reactive silyl complex of this ligand contains two silyl and one hydride ligands and by kinetic analysis of the catalytic reaction determine the rate-limiting step for arenes with varying electronic properties. Computational studies indicate that the steric encumberance of the phenanthroline ligand controls the number of silyl ligands bound to iridium and that the difference in the number of silyl ligands leads to large differences to the rates of the reaction. These studies provide insight into the origins of the high activity of the catalyst containing the 2,9-Me₂Phen ligand.</p>

A two-coordinate Ni(i) silyl complex: CO2 insertion and oxidatively-induced silyl migrations

Synthesis of the first open-shell two-coordinate silyl complex and its oxidatively-induced silyl rearrangements.

Crystal structure of tricarbonyl(μ-diphenylphosphido-κ2P:P)(methyldiphenylsilyl-κSi)bis(triphenylphosphane-κP)iron(II)platinum(0)(Fe—Pt)

The title compound, [FePt(C12H10P)(C13H13Si)(C18H15P)2(CO)3]·0.5CH2Cl2, represents an example of a phosphido-bridged heterobimetallic silyl complex; these are interesting precursors for the coordination and activation of small unsaturated organic molecules. The μ2-PPh2ligand spans the iron and platinum atoms, which are connectedviaa metal–metal bond of 2.7738 (4) Å. In contrast to most other complexes of the [(OC)3Fe(SiR3)(μ-PR2)PtL2] family, where the iron-bound SiR3group istrans-arranged with respect to the μ2-PPh2ligand, the SiPh2Me ligand is roughly collinear with the Fe–Pt vector [Si—Fe—Pt = 169.07 (3)°].

Consecutive C–F bond activation and C–F bond formation of heteroaromatics at rhodium: the peculiar role of FSi(OEt)3

C–F activation reactions for a silyl complex gave fluorosilane and Rh pyridyl complexes. In consecutive reactions, the fluorosilane can act as a fluoride source and a regeneration of the C–F bond occurs by Si–F bond cleavage. This sets back the C–F bond cleavage reaction with consequences for the overall chemoselectivity of the activation reactions.