Nature of M-(eta(2)-H-SiR2) bonds in chromium, molybdenum and tungsten complexes [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiR2)] and [(eta(5)-C5H5)(CO)(2)M(eta(2)-H-SiMe2)]: A theoretical study

作者：Pandey Krishna K^*

来源：Polyhedron, 2013, 55: 241-248.

DOI：10.1016/j.poly.2013.03.034

• Sigma-silyl
• Structure
• Bonding
• Chromium
• Molybdenum
• Tungsten

Geometries, electronic structure, and bonding analysis of the coordinated hydrosilyl groups in chromium, molybdenum and tungsten complexes [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiMe2)] (1Cr, M = Cr; 1Mo, M = Mo; 1W, M = W), [(eta(5)-C5H5)(CO)(2)M(eta(2)-H-SiMe2)] (2Cr, M = Cr; 2Mo, M = Mo; 2W, M = W), [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiEt2)] (3Mo) [(eta(5)-C5H5)(dmpe)Mo(eta(2)-H-SiPh2)] (4Mo) and [(eta(5)-C5H5)(dmpe)M(eta(2)-H-Si(H)Ph)] (5Mo) (dmpe = Me2PCH2CH2PMe2) were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The optimized geometry of model complexes for [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiMe2)], [(eta(5)-C5H5)(dmpe)M(eta(2)-H-SiEt2)] and [(eta(5)-C5H5)(dmpe)M(eta(2)-H-Si(H)Ph)] are in excellent agreement with the experimental values. The M-H1 bond is directed toward the empty p orbital of the Si atom of the silylene ligands. A significant lengthening of the M-H1 and Si-H1 bonds and small Si-M-H1 bond angles (in the range 45.4 degrees-47.5 degrees) indicate the existence of three center two electron M-H-Si bonding. Upon substitution of the dmpe ligand by better pi-acceptor CO ligands, the calculated M-Si and M-H1 bond distances slightly increase, while Si-H1 bond distances decrease due to increase in M <- SiR2 sigma-bonding. The small values of Mayer bond orders of the M-H and H-Si bonds also indicate the hydride as bridging between the M and Si centers. The M-H-Si bonding orbital is polarized toward the H1 atom (the H1 atom contributes nearly 50% to the M-H-Si bonding orbital). Absolute values of various energy terms increase upon substitution of dmpe ligand by better pi-acidic CO ligands. The nature of substituent at Si atom in complexes 1Mo, 3Mo-5Mo has a small effect on the orbital interaction, Delta E-orb.

• 出版日期2013-5-17