Covalent bonding interactions between the Lewis acid and Lewis base functionalities have been probed in a series of "frustrated Lewis pairs" (FLPs) (mainly substituted vinylene linked intramolecular phosphane−borane adducts), using solid-state nuclear magnetic resonance techniques and accompanying DFT calculations. Both the 11 B NMR isotropic chemical shifts and nuclear electric quadrupolar coupling parameters turn out to be extremely sensitive experimental probes for such interactions, revealing linear correlations with boron−phosphorus internuclear distances. The principal component V zz of the 11

The conjugated frustrated phosphane/borane Lewis pairs formed by 1,1-carboboration of a substituted diphenylphosphino acetylene, undergo a synergistic 1,1-addition reaction to n-butyl isocyanide with formation of new B-C and P-C bonds to the former isonitrile carbon atom. Using tert-butyl isocyanide dynamic behaviour between the isocyanide-[B] adduct and the 1,1-addition product formation was observed in solution. The different modes of isocyanide binding to the FLPs in the solid state were characterized using X-ray crystal structure analyses and comprehensive 11 B and 31 P solid-state magicangle-spinning (MAS-) NMR experiments. The free FLP, the Lewis adduct at the borane group, and the cyclic product resulting from isocyanide addition to both reaction centers, can be differentiated via 11 B and 31 P isotropic chemical shifts, 11 B nuclear electric quadrupole coupling constants, isotropic indirect 11 B-31 P spin-spin coupling constants, and 11 B/ 31 P internuclear distances measured by rotational echo double resonance.

We report the addition of M–H bonds (M = Al, Zn, Mg) to a Rh(iii) intermediate generated from the reductive elimination of triethylsilane from [Cp*Rh(H)2(SiEt3)2].

A series of diarylphosphinyl-substituted acetylenes of the type (aryl)(2)P-C≡C-R (aryl = phenyl or mesityl, R = Ph or n-propyl) react with the strongly Lewis acid reagent B(C(6)F(5))(3) in toluene at elevated temperatures (70-105 °C) to give the 1,1-carboboration products 4. Treatment of bis(diphenylphosphinyl)acetylene with B(C(6)F(5))(3) under analogous conditions proceeded with phosphinyl migration to yield the 1,1-carboboration product 4d, bearing a geminal pair of Ph(2)P substituents at one former acetylene carbon atom and a C(6)F(5) substituent and the remaining -B(C(6)F(5))(2) group at the other. Prolonged thermolysis of 4d resulted in an intramolecular aromatic substitution reaction by means of Ph(2)P attack on the adjacent C(6)F(5) ring to yield the zwitterionic phospha-indene derivative 7. The compounds 4a, 4c, 4d, and 7 were characterized by X-ray diffraction.

Through a dramatic advance in the coordination chemistry of the zinc-hydride bond, we describe the trajectory for the approach of this bond to transition metals. The dynamic reaction coordinate was interrogated through analysis of a series of solid state structures and is one in which the TM-H-Zn angle becomes increasingly acute as the TM---Zn distance decreases. Parallels may be drawn with the oxidative addition of boron-hydrogen and silicon-hydrogen bonds to transition metal centers.Appreciation of the trajectory for the approach of carbon-hydrogen bonds to transition metals has led to a deeper understanding of catalytic processes involving the breaking of carbon-hydrogen bonds. [1] As the C-H bond advances towards the metal, formation of an intermediate σ-complex can preface oxidative addition. [2] Many authors have described a continuum between the σ-complex and oxidative addition product. [2][3] As the M---C distance decreases, the H-M-C angle becomes increasingly acute and electron density is transferred from both the d-orbitals of the metal and breaking C-H bond to the forming M-C and M-H bonds. Alkanes are not privileged in this regard, σ-borane and σ-silane complexes have an extensive chemistry and the relationship between them and the oxidative addition products metal boryls and metal silyls is well understood (Figure 1). [4] In comparison there is only limited precedent for the coordination of zinc hydrides to transition metal centers. Kubas and Shriver have commented on the nature of hydride-bridged zincate complexes in solution. [5] The proposition that these species could dimerize by 3-center 2-electron bonds seeded ideas that ultimately led to the discovery of dihydrogen complexes. [6] A handful of heterobimetallic complexes containing transition metal and zinc centers bridged by hydride ligands are known, [7][8][9][10][11][12][13][14] The majority however, include more than one bridging hydride ligand clouding analysis of the TM-H-Zn group. Through kinetic protection of a zinc center with a sterically demanding ligand, we recently isolated a rare example of a heterobimetallic complex possessing an unsupported Cu-H-Zn moiety. [15] Here we describe an advance in the coordination chemistry of the zinc hydride bond to transition metals. Through analysis of a series of solid state structures and calculations, we describe the reaction trajectory for the approach of a single zinc-hydride bond to a transition metal.Photolysis . While a similar protocol could not be used to synthesize the tungsten pentacarbonyl complex 2c, photolysis of [W(CO)6] in d8-THF for 6h followed by addition of 1 gave the desired product. The rhodium complex 5b was prepared by in situ generation of [Cp*Rh(H)2(SiEt3)(ZnBDI)] (5a) [10a] followed by photolysis in the presence of excess PMe3 (BDI = {2,6-i Pr2C6H3NCMe}2CH). A series of increasingly electron-rich ligands were included on the transition metal fragments to allow variation of the electron density at the TM center.The new heterobimetallic complexes 2-5 poss...

Reaction of the acetylene Mes(2)P-C≡C-Ar with B(C(6)F(5))(3) at rt gives a zwitterionic phosphirenium product, which reacts further at >100 °C to complete the 1,1-carboboration reaction.

[Cp*RhCl(μ-Cl)]2 is reported as a highly efficient and selective precatalyst for the hydrodefluorination of perfluoroarenes using a hydrocarbon-soluble aluminum dihydride as the terminal reductant. Reactions are directed to cleave a C–F bond adjacent to an existing C–H bond with high regioselectivity (98.5–99%). A heterobimetallic complex containing an extremely rare Al–H–Rh functional group has been isolated and shown to be catalytically competent.

Simple alkenylbis(pentafluorophenyl)boranes undergo 1,1-alkenylboration with phosphanylacetylenes to give phosphane-borane Lewis pairs with a conjugated diene backbone.