Carbon−Hydrogen and Carbon−Carbon Bond Activation of Cyclopropane by a Hydridotris(pyrazolyl)borate Rhodium Complex

Abstract

Generation of the 16-electron fragment {[HB (3,5-dimethylpyrazolyl) 3 ]Rh(CNCH 2 CMe 3 )} (Tp′RhL) in the presence of cyclopropane results in C-H activation of the hydrocarbon. The cyclopropyl hydride complex rearranges in benzene solvent to the metallacyclobutane complex Tp′Rh(CNCH 2 CMe 3 )(CH 2 CH 2 CH 2 ). Thermolysis of the rhodacyclobutane complex produces an η 2 -propylene complex. The related complex Tp′Rh(CN-2,6-xylyl)(C 2 H 4 ) has been structurally characterized and displays η 3 -Tp′ coordination, both in the solid state and in solution. Thermolysis of the rhodacyclobutane complex in the presence of neopentyl isocyanide leads to insertion of isocyanide into both Rh-C bonds of the metallacycle. Cyclobutane undergoes C-H but not C-C bond cleavage.

Transition Metal Mediated C–H Activation and Functionalization: The Role of Poly(pyrazolyl)borate and Poly(pyrazolyl)alkane Ligands

“…The Jones group has utilized the hydridotris(3,5‐dimethylpyrazyolyl)borate ligand (Tp*) to explore stoichiometric C–H bond activations . [Tp*Rh(CNneo)(PhN=C=Nneo)] (neo = neopentyl, –CH 2 CMe 3 ) has been used to determine kinetic selectivity toward C–H bond activations of alkanes and aromatics as well as M–C bond strengths for cyclic and acyclic hydrocarbons . As shown in Scheme , the complex [Tp*Rh(CNneo)(PhN=C=Nneo)] can facilitate C–H bond activation of a number of hydrocarbon substrates under photolytic conditions through initial dissociation of the carbodiimide ligand and generation of an open coordination site for σ(C,H)‐alkane coordination prior to oxidative addition to produce [Tp*Rh(CNneo)(R)(H)].…”

“…The reactivity of [Tp*Rh(CNneo)(PhN=C=Nneo)] with different C–H bonds has been extended to include multiple hydrocarbons ranging from aromatic,, sp, sp 2 , and sp 3 ‐hybridized C–H bonds to cycloalkanes , , . Also, the effects of heteroatoms and nitrile functional groups in the hydrocarbon undergoing C–H activation have been studied .…”

The Effects of Ancillary Ligands on Metal–Carbon Bond Strengths as Determined by C–H Activation

“…For linear hydrocarbons, a kinetic preference was observed for the exclusive activation of the C-H bonds of the terminal methyl groups. The activation of secondary C-H bonds was only observed when no other primary C-H bonds were available (e.g., cyclohexane, cyclopentane, cyclopropane [10]). With mesitylene, both aromatic and benzylic C-H bonds were cleaved.…”

Investigation of C–C Bond Activation of sp–sp2 C–C Bonds of Acetylene Derivatives via Photolysis of Pt Complexes

“…Data for 9 are as follows. 1 Preparation of (dippe)Pt(Ph)(CCCCPh) (10). Compound 9 (10 mg, 15.2 × 10 −3 mmol) was dissolved in 1 mL of C 6 D 6 and placed into a resealable NMR tube.…”