Nature of M-Ga Bonds in Dihalogallyl Complexes (eta(5)-C5H5)(Me3P)(2)M(GaX2) (M = Fe, Ru, Os) and (eta(5)-C5H5)(OC)(2)Fe(GaX2) (X = Cl, Br, I): A DFT Study

作者：Pandey Krishna K^*; Patidar Pankaj; Aldridge Simon

来源：Journal of Physical Chemistry A, 2010, 114(45): 12099-12105.

DOI：10.1021/jp1073297

Density functional theory (DFT) calculations have been performed on the terminal dihalogallyl complexes of iron, ruthenium, and osmium (eta(5)-C5H5)(Me3P)(2)M(GaX2) (M = Fe, Ru, Os; X = Cl, Br, I) and (eta(5)-C5H5)(OC)(2)Fe(GaX2) (X = Cl, Br, I) at the BP86/TZ2P/ZORA level of theory. On the basis of analyses suggested by Pauling, the M-Ga bonds in all of the dihalogallyl complexes are shorter than M-Ga single bonds; moreover, on going from X = Cl to X = 1, the optimized M-Ga bond distances are found to increase. From the perspective of covalent bonding, however, pi-symmetry contributions are, in all complexes, significantly smaller than the corresponding sigma-bonding contribution, representing only 4-10% of the total orbital interaction. Thus, in these GaX2 complexes, the gallyl ligand behaves predominantly as a sigma donor, and the short M-Ga bond lengths can be attributed to high gallium s-orbital character in the M-Ga sigma-bonding orbitals. The natural population analysis (NPA) charge distributions indicate that the group 8 metal atom carries a negative charge (from -1.38 to -1.62) and the gallium atom carries a significant positive charge in all cases (from +0.76 to +1.18). Moreover, the contributions of the electrostatic interaction terms (Delta E-elstat) are significantly larger in all gallyl complexes than the covalent bonding term (Delta E-orb): thus, the M-Ga bonds have predominantly ionic character (60-72%). The magnitude of the charge separation is greatest for dichlorogallyl complexes (compared to the corresponding GaBr2 and GaI2 systems), leading to a larger attractive Delta E-elstat term and to M-Ga bonds that are stronger and marginally shorter than in the dibromo and diiodo analogues.

• 出版日期2010-11-18