A half-century of nonclassical organometallic chemistry: a personal perspective

A review of some developments in transition metal (nonclassical) organometallic chemistry is presented, with emphasis on areas to which the author himself has made major and/or seminal contributions: especially fluxional organometallics, fluxional metal carbonyls, and the discovery and full explanation of agostic hydrogen atoms. An effort has been made to present these topics from the perspective of today rather than in strictly chronological order, with a sufficient number of specific examples to be concrete, but by no means encyclopedic. Particular topics covered are "ring whizzers", concerted shifts of two or more CO ligands, twirling M(CO)(3) groups, and merry-go-rounds. In addition, the following topics are discussed: the unfinished business of mu(2),eta(2),eta(2)-ethene complexes and arene complexes of the lanthanides and actinides.