S. Dapprich et G. Frenking, TRANSITION-METAL COMPLEXES WITH MORE THAN ONE DIHYDROGEN LIGAND - STRUCTURE AND BONDING OF M(CO)(6-X)(H-2)(X) (M=CR, MO, W, X=1, 2, 3), Zeitschrift fur anorganische und allgemeine Chemie, 624(4), 1998, pp. 583-589
Citations number
49
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Zeitschrift fur anorganische und allgemeine Chemie
Quantum mechanical ab initio calculations at the MP2 and CCSD(T) level
of theory have been used to investigate the geometries and bond energ
ies of the complexes M(CO)(6-x)(H-2)(x) (M = Cr, Mo, W; x = 1, 2, 3).
The theoretically predicted M(CO)(5)-(H-2) bond dissociation energies
are in excellent agreement with experimental values. The M-(H-2) disso
ciation energies of the bis- and tris-dihydrogen complexes are very si
milar to the values for the mono-dihydrogen complexes. In M(CO)(5)(H-2
) the dihydrogen ligand prefers an eclipsed conformation relative to t
he equatorial carbonyl groups. For M(CO)(4)(H-2)(2) the cis and trans
isomers are nearly equal in energy for M = W, while a cis configuratio
n is favoured for M = Cr. For M(CO)(3)(H-2)(3) the facial configuratio
ns are more stable than the meridial structures for all three metals M
. The charge decomposition analysis (CDA) classifies dihydrogen as a d
onor ligand with moderate acceptor properties. In trans-M(CO)(4)(H-2)(
2) back donation is increased and the M-(H-2) bonds are stronger than
in M(CO)(5)-(H-2). Back donation in M(CO)(3)(H-2)(3) is slightly weake
r than in the mono-dihydrogen complexes M(CO)(5)(H-2).