Structure and bonding of metallacyclocumulenes, radialenes, butadiyne complexes and their possible interconversion: a theoretical study

Density functional theory is used to study the dimerization of metallacyclo cumulenes (1, 2 and 9) to metal substituted radialenes (3, 4 and 5). These were compared to the dimerization of ethylene to cyclobutane and cumulene t o radialene, The bonding of the metallacyclocumulenes were discussed in the light of the Dewar-Chatt-Duncanson model. A possible mechanism for the for mation of bis(butadiyne) complex of Ni (8) is also presented. Correlation d iagrams constructed for the conversion of the radialene type structure to t hat of the bis(butadiyne) complex show that it is allowed for both Ti and N i. (C) 2001 Published by Elsevier Science B.V.