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π-Donor-substituted metallacumulenes of chromium and tungsten

✍ Scribed by Helmut Fischer; Normen Szesni

Publisher
Elsevier Science
Year
2004
Tongue
English
Weight
398 KB
Volume
248
Category
Article
ISSN
0010-8545

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✦ Synopsis

The review describes the synthesis of -donor-substituted carbonyl metallacumulenes [(CO) 5 M=(C=C=) x C(R 1 )R 2 ] (x = 1: allenylidene complexes; x = 2: pentatetraenylidene complexes) of chromium and tungsten. The -donating properties of the substituents at one end of the carbon chain have been varied through employing different combinations of R 1 (Ph, OR, NR 2 ) and R 2 (Ph, OR, NR 2 ). The back-bonding properties of the metal-ligand fragment at the other end of the chain have been changed by displacing carbonyl ligands by P-, As-, or Sb-donor ligands. The influence of varying these two parameters on the spectroscopic properties, the bonding within the metallacumulene chain, and the reactivity is evaluated. The reactivity of these metallacumulenes and the selectivity of reactions with various P-, N-and C-nucleophiles as well as the selectivity in reactions with ynamines are described. Examples for applying some of these reactions to the synthesis of heterocyclic ligands are given.

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