Activation ofAlkanes with Organotransition MetalComplexes

Summary. Alkanes, although plentiful enough tobeconsidered foruseasfeedstocks inlarge-scale chemical processes, aresounreactive thatrelatively few chemical reagents havebeendeveloped toconvert themtomolecules having useful functional groups. However, arecently synthesized iridium (Ir) complex successfully converts alkanes into hydridoalkylmetal complexes (M+ R-H-* R-M-H). Thisisa dihydride having theformula Cp*(L)lrH2, whereCp*andLareabbreviations forthe ligands (CH3)5C5 and(CH3)3P, respectively. Irradiation with ultraviolet light causes the dihydride toloseH2,generating thereactive intermediate Cp*lrL. Thisintermediate reacts rapidly withC-Hbondsinevery molecule sofar tested (including alkanes) and leads tohydridoalkylirid ium complexes Cp*(L)lr(R)(H). Evidence hasbeenobtained thatthis C-Hinsertion, oroxidative addition, reaction proceeds through asimple three-center transition state anddoesnotinvolve organic free radicals asintermediates. Thustheintermediate Cp*lrL reacts mostrapidly withC-Hbondshaving relatively highbondenergies, suchasthose atprimary carbon centers, insmall organic rings, andinaromatic rings. This contrasts directly with thetypeofhydrogen