C-F Bond Activation by Silylium Cation/Phosphine Frustrated Lewis Pairs: Mono-Hydrodefluorination of PhCF , PhCF H and Ph CF.

Single defluorination of aryl polyfluoromethyl functionalities is achieved by both intra- and intermolecular silylium cation/phosphine Lewis pairs. Phosphine-captured aryl fluoromethyl cations are then treated with Brønsted base to complete the first mono-hydrodefluorinations of PhCF , Ph CF , and PhCF .

A model for C-F activation by electrophilic phosphonium cations.

The synthesis of the electrophilic phosphonium cation (EPC) salt [CH(CF)PF(CF)][B(CF)] 4 was achieved via oxidation of phosphine [CH(CF)P(CF)] 2 with XeF to form phosphorane [CH(CF)PF(CF)] 3 and subsequent fluoride ion abstraction. Structural and spectroscopic characterization of 4 provides evidence of an interaction between the CF functionality and the phosphonium centre. AIM and NBO analyses also support donation from a lone pair on a fluorine atom of the CF group to the P-F σ* orbital of the fluorophosphonium unit, consistent with previously proposed mechanisms for main group C-F bond activations.

Ferrocenyl-derived electrophilic phosphonium cations (EPCs) as Lewis acid catalysts.

Oxidation of diphenylphosphinoferrocene and 1,1'-bis(diphenylphosphino)ferrocene with XeF2, resulted in the formation of CpFe(η(5)-C5H4PF2Ph2) 1 and Fe(η(5)-C5H4PF2Ph2)22 respectively. Subsequent reactions with [SiEt3][B(C6F5)4] yielded [CpFe(η(5)-C5H4PFPh2)][B(C6F5)4] 3 and [Fe(η(5)-C5H4PFPh2)2] [B(C6F5)4]24. PhP(η(5)-C5H4)2Fe 5 was prepared, converted to [PhMeP(η(5)-C5H4)2Fe][O3SCF3] 6 and then to [PhMeP(η(5)-C5H4)2Fe][B(C6F5)4] 7.

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations.

Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods.

1,2-Diphosphonium dication: a strong P-based Lewis acid in frustrated lewis pair (FLP)-activations of B-H, Si-H, C-H, and H-H bonds.

A highly Lewis acidic diphosphonium dication [(C10H6)(Ph2P)2](2+) (1), in combination with a Lewis basic phosphine, acts as a purely phosphorus-based frustrated Lewis pair (FLP) and abstracts hydride from [HB(C6F5)3](-) and Et3SiH demonstrating the remarkable hydridophilicity of 1. The P-based FLP is also shown to activate H2 and C-H bonds.

Phosphinimine-substituted boranes and borenium ions.

The phosphinimines R3PNSiMe3 (R = t-Bu: 1a, R = Cy: 1b, R = Et: 1c, R = Ph: 1d) are reacted with a series of chloro and fluoroboranes (9Cl-9-BBN, (C6F5)2BCl, PhBCl2 and Mes2BF) to access a family of phosphinimine-substituted boranes (2a-d, 3b-d, 4c,d and 6a,b) via Me3SiX elimination (X = Cl, F). The steric and electronic factors governing the formation of monomeric or dimeric products (7c,d) are presented. In addition, in some cases a Lewis acid mediated exchange of Si-bonded methyl groups for a chloro-substituent was observed (5a,b).

Three-coordinate beryllium β-diketiminates: synthesis and reduction chemistry.

A series of mononuclear, heteroleptic beryllium complexes supported by the monoanionic β-diketiminate ligand [HC{CMeNDipp}(2)](-) (L; Dipp = 2,6-diisopropylphenyl) have been synthesized. Halide complexes of the form [LBeX] (X = Cl, I) and a bis(trimethylsilyl)amide complex were produced via salt metathesis routes. Alkylberyllium β-diketiminate complexes of the form [LBeR] (R = Me, (n)Bu) were obtained by salt metathesis from the chloride precursor [LBeCl].

Disproportionation and radical formation in the coordination of "GaI" with bis(imino)pyridines.

Attempted coordination of "Ga(I)I" with two new sterically bulky, aryl substituted bis(imino)pyridine ligands lead to Ga(III) species [2,6-{ArN=CPh}(2)(NC(5)H(3))]GaI(2)(+)GaI(4)(-) (Ar = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3) = Dipp) arising from thermodynamically favorable disproportionation reactions. Examination of these reactions lead to isolation of a neutral radical species [2,6-{DippN=CPh}(2)(NC(5)H(3))]GaI(2). Both EPR spectroscopy and DFT calculations on this compound indicate that the unpaired electron is localized in a di(imino)pyridine pi* orbital of an anionic ligand with nearly zero contribution from the Ga or I centers.