Transition Metal Complexes with more than one Dihydrogen Ligand: Structure and Bonding of M(CO)6–x(H2)x (M = Cr, Mo, W; x = 1, 2, 3) [1]

✍ Scribed by Stefan Dapprich; Gernot Frenking

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: German
• Weight: 189 KB
• Volume: 624
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/(sici)1521-3749(199804)624:4<583::aid-zaac583>3.0.co;2-p

✦ Synopsis

Quantum mechanical ab initio calculations at the MP2 and CCSD(T) level of theory have been used to investigate the geometries and bond energies 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 ) dissociation energies of the bis-and tris-dihydrogen complexes are very similar to the values for the mono-dihydrogen complexes. In M(CO) 5 (H 2 ) the dihydrogen ligand prefers an eclipsed conformation relative to the 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 configura-tion is favoured for M = Cr. For M(CO) 3 (H 2 ) 3 the facial configurations are more stable than the meridial structures for all three metals M. The charge decomposition analysis (CDA) classifies dihydrogen as a donor 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 weaker than in the mono-dihydrogen complexes M(CO) 5 (H 2 ).