Selective Functionalization of a Variety of Hydrocarbon C(sp³)–H Bonds Initiated by Cp*W(NO)(CH₂CMe₃)(η³-CH₂CHCHPh)

Abstract

Cp*W(NO)(CH 2 CMe 3 )(η 3 -CH 2 CHCHPh) (1) effects C(sp 3 )−H activations of methane, ethane, propane, and n-butane exclusively at their terminal carbons and forms the corresponding Cp*W(NO)(alkyl)(η 3 -CH 2 -CHCHPh) complexes. It also activates (n-Bu) 2 O, 1-chloropropane, and Me 4 Si in a similar manner. Exposure of the Cp*W(NO)(alkyl)(η 3 -CH 2 CHCHPh) complexes to carbon monoxide results in initial 1,1-CO insertion into the newly formed tungsten−alkyl bonds and formation of the corresponding η 1 -acyl complexes, some of which can be isolated. Additional functionalization of the C−H activation products occurs upon exposure to CO under more forcing conditions. Such treatment produces η 2 -bound unsaturated-ketone complexes resulting from CO insertion into the W−alkyl σ bonds followed by cross-coupling of the η 1 -acyl and the η 3 -allyl ligands and coordination of CO at the resulting vacant coordination site at tungsten. The unsaturated ketones can be released from the metal's coordination spheres either by photolysis of the complexes in MeCN or by further exposure of them to CO. All new compounds have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of six of them have been established by single-crystal X-ray crystallographic analyses.

Foreword for the Special Issue “Hydrocarbon Chemistry: Activation and Beyond”. Responsible or Irresponsible Use of Hydrocarbons? You Be the Judge!

“…A well established pillar of organometallic chemistry has been the preparation of reactive metal–carbon bonds (or multiple bonds) that promote C–H activation reactions of hydrocarbons. − In this vein, is a series of papers involving the highly electropositive transition and lanthanide metal ions. Legzdins and co-workers , publish back-to-back manuscripts that describe the use of well-defined tungsten complexes that can activate and subsequently functionalize hydrocarbons (including methane) . Speaking of methane, one major impediment to utilization of this valuable resource is the limited understanding of its reactivity in the gas phase.…”

Stabilization of propene molybdenum and tungsten half–sandwich complexes by intramolecular coordination of a thioether function

“…18 Alkene intermediates are formed upon C-H activation of hydrocarbons by cyclopentadienyl tungsten complexes [(h 5 -Cp*)W(NO)(R)(h 3 -allyl)] (Cp* = C 5 Me 5 ; R = H, neopentyl), as documented on adducts bearing trapped carbon monoxide [(h 5 -Cp*)W(NO)(CO)(h 2 -alkene)] (Scheme 1, reaction A). 19,20 exchanged by labile ligands (e.g., dimethyl sulde) while stronger ligands (e.g., acetonitrile) induce h 3 -to-h 5 -indenyl ring slippage. 21 The aim of this work is to describe stabilizing effects of the intramolecular coordination on cyclopentadienyl molybdenum and tungsten complexes without an annulated benzene ring.…”

“…Alkene intermediates are formed upon C–H activation of hydrocarbons by cyclopentadienyl tungsten complexes [(η 5 -Cp*)W(NO)(R)(η 3 -allyl)] (Cp* = C 5 Me 5 ; R = H, neopentyl), as documented on adducts bearing trapped carbon monoxide [(η 5 -Cp*)W(NO)(CO)(η 2 -alkene)] (Scheme 1, reaction A). 19,20…”