Premium
Transition Metal Complexation of σ Bonds
Author(s) -
Crabtree Robert H.
Publication year - 1993
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199307891
Subject(s) - agostic interaction , chemistry , transition metal , crystallography , metathesis , atom (system on chip) , catalysis , sigma bond , metal , stereochemistry , organometallic chemistry , chemical bond , crystal structure , polymerization , organic chemistry , polymer , computer science , embedded system
Abstract The first σ complexes were found in the 1960s and 1970s, but they did not attract more than passing attention. Only now are we beginning to recognize their key role in the chemical reactions of σ bonds, and this has encouraged more detailed study. In contrast with the more familiar π‐donor complexes such as M(CH 2 CH 2 ) and complexes like MNH 3 , in which the one pair of electrons on the N atom is bound to the metal atom, in a σ complex an XH group binds to the transition metal atom; the XH σ‐bonding electron pair acts as a 2e donor to give an (X‐H)‐M type complex. Dihydrogen complexes (X = H) are one important group of σ complexes. C‐H‐M complexes (X = R 3 C) with an agostic C‐H‐M interaction have not only been found in the ground state but also implicated in the transition states of many important organometallic transformations such as Ziegler–Natta catalysis and sigma bond metathesis. The importance of XH bond activation will encourage continued growth in this field.