Cho Han-Gook, Andrews Lester
Department of Chemistry, University of Incheon, 177 Dohwa-dong, Nam-ku, Incheon, 402-749, South Korea.
J Phys Chem A. 2007 Apr 5;111(13):2480-91. doi: 10.1021/jp067662g. Epub 2007 Mar 9.
Reactions of laser-ablated group 3 metal atoms with methyl halides have been carried out in excess of Ar during condensation and the matrix infrared spectra studied. The metals are as effective as other early transition metals in providing insertion products (CH3-MX) and higher oxidation state methylidene complexes (CH2-MHX) (X = F, Cl, Br) following alpha-hydrogen migration. Unlike the cases of the group 4-6 metals, the calculated methylidene complex structures show little evidence for agostic distortion, consistent with the previously studied group 3 metal methylidene hydrides, and the C-M bond lengths of the insertion and methylidene complexes are comparable to each other. However, the C-Sc bond lengths are 0.013, 0.025, and 0.029 A shorter for the CH2-ScHX complexes, respectively, and the spin densities are consistent with weak C(2p)-Sc(3d) pi bonding. The present results reconfirm that the number of valence electrons on the metal is important for agostic interaction in simple methylidene complexes.
在冷凝过程中，在过量氩气存在的情况下，对激光烧蚀的第3族金属原子与卤代甲烷的反应进行了研究，并对基质红外光谱进行了分析。这些金属在提供插入产物（CH3-MX）和经过α-氢迁移后的高氧化态亚甲基配合物（CH2-MHX）（X = F、Cl、Br）方面与其他早期过渡金属一样有效。与第4 - 6族金属的情况不同，计算得到的亚甲基配合物结构几乎没有显示出螯合畸变的迹象，这与之前研究的第3族金属亚甲基氢化物一致，并且插入配合物和亚甲基配合物的C - M键长彼此相当。然而，对于CH2-ScHX配合物，C - Sc键长分别短0.013、0.025和0.029 Å，并且自旋密度与弱的C(2p)-Sc(3d) π键合一致。目前的结果再次证实，金属上价电子的数量对于简单亚甲基配合物中的螯合相互作用很重要。
