Bonding Analysis of Metal鈭扢etal Multiple Bonds in R3M鈭扢鈥睷3 (M, M鈥?= Cr, Mo, W; R = Cl, NMe2)

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• 作者：Nozomi Takagi ; Andreas Krapp ; Gernot Frenking
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：February 7, 2011
• 年：2011
• 卷：50
• 期：3
• 页码：819-826
• 全文大小：838K
• 年卷期：v.50,no.3(February 7, 2011)
• ISSN：1520-510X

文摘

The bonding situation of homonuclear and heteronuclear metal鈭抦etal multiple bonds in R₃M鈭扢鈥睷₃ (M, M鈥?= Cr, Mo, W; R = Cl, NMe₂) is investigated by density functional theory (DFT) calculations, with the help of energy decomposition analysis (EDA). The M鈭扢鈥?bond strength increases as M and M鈥?become heavier. The strongest bond is predicted for the 5d鈭?d tungsten complexes (NMe₂)₃W鈭扺(NMe₂)₃ (D_e = 103.6 kcal/mol) and Cl₃W鈭扺Cl₃ (D_e = 99.8 kcal/mol). Although the heteronuclear molecules with polar M鈭扢鈥?bonds are not known experimentally, the predicted bond dissociation energies of up to 94.1 kcal/mol for (NMe₂)₃Mo鈭扺(NMe₂)₃ indicate that they are stable enough to be isolated in the condensed phase. The results of the EDA show that the stronger R₃M鈭扢鈥睷₃ bonds for heavier metal atoms can be ascribed to the larger electrostatic interaction caused by effective attraction between the expanding valence orbitals in one metal atom and the more positively charged nucleus in the other metal atom. The orbital interaction reveal that the covalency of the homonuclear and heteronuclear R₃M鈭扢鈥睷₃ bonds is due to genuine triple bonds with one 蟽- and one degenerate 蟺-symmetric component. The metal鈭抦etal bonds may be classified as triple bonds where 蟺-bonding is much stronger than 蟽-bonding; however, the largest attraction comes from the quasiclassical contribution to the metal鈭抦etal bonding. The heterodimetallic species show only moderate polarity and their properties and stabilities are intermediate between the corresponding homodimetallic species, a fact which should allow for the experimental isolation of heterodinuclear species. CASPT2 calculations of Cl₃M鈭扢Cl₃ (M = Cr, Mo, W) support the assignment of the molecules as triply bonded systems.