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Diene, Alkyne, Alkene, and Alkyl Complexes of Early Transition Metals: Structures and Synthetic Applications in Organic and Polymer Chemistry
Author(s) -
Yasuda Hajime,
Nakamura Akira
Publication year - 1987
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.198707231
Subject(s) - diene , alkene , chemistry , alkyne , reactivity (psychology) , alkyl , transition metal , polymer chemistry , catalysis , organic chemistry , medicine , natural rubber , alternative medicine , pathology
An unprecedented series of highly reactive alkene‐and diene‐complexes of the early transition metals (Groups 3A–5A of the periodic system) have been isolated recently. Diene complexes of this sort (M Ti, Zr, Hf, Nb, Ta) prefer, besides the (η 4 ‐s‐ cis ‐diene)metal structure, either a novel bent η 4 ‐metallacyclo‐3‐pentene structure or the unique (η 4 ‐s‐ trans ‐diene)metal structure. In bis(diene)metal complexes of Nb and Ta the η 4 ‐s‐ cis ‐dienes assume an unusual exo‐endo ( supine‐prone ) geometry. The MC bonds in these diene‐metal complexes generally exhibit highly polarized σ‐bonding along with π‐bonding character. The complexes therefore undergo a variety of regio‐ and stereoselective carbometalations with substrates containing CC, CO, or CN multiple bonds. Examples of the products that can be obtained include ketones, vinyl ketones, unsaturated primary, secondary, and tertiary alcohols, as well as diols and unsaturated acids. Mechanistic studies on the stoichiometric and catalytic conversions of unsaturated hydrocarbons provides, inter alia, some insights into the course of polymerization reactions.