Organometallics: Materials and Catalysis, Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS - University of Rennes 1, 35042 Cedex, Rennes, France.
Dalton Trans. 2014 Mar 21;43(11):4268-86. doi: 10.1039/c3dt51681d.
Stable germanium(II) and lead(II) amido complexes {LO(i)}M(N(SiMe3)2) (M = Ge(II), Pb(II)) bearing amino(ether)phenolate ligands are readily available using the proteo-ligands {LO(i)}H of general formula 2-CH2NR2-4,6-tBu2-C6H2OH (i = 1, NR2 = N((CH2)2OCH3)2; i = 2, NR2 = NEt2; i = 3, NR2 = aza-15-crown-5) and M(N(SiMe3)2)2 precursors. The molecular structures of these germylenes and plumbylenes, as well as those of {LO(3)}GeCl, {LO(3)}SnCl and of the congeneric {LO(4)}Sn(II)(N(SiMe3)2) where NR2 = aza-12-crown-4, have been determined crystallographically. All complexes are monomeric, with 3-coordinate metal centres. The phenolate systematically acts as a N^O(phenolate) bidentate ligand, with no interactions between the metal and the O(side-arm) atoms in these cases (for {LO(1)}(-), {LO(3)}(-) and {LO(4)}(-)) where they could potentially arise. For each family, the lone pair of electrons essentially features ns(2) character, and there is little, if any, hybridization of the valence orbitals. Heterobimetallic complexes {LO(3)}M(N(SiMe3)2)·LiOTf, where the Li(+) cation sits inside the tethered crown-ether, were prepared by reaction of {LO(3)}M(N(SiMe3)2) and LiOTf (M = Ge(II), Sn(II)). The inclusion of Li(+) (featuring a close contact with the triflate anion) in the macrocycle bears no influence on the coordination sphere of the divalent tetrel element. In association with iPrOH, the amido germylenes, stannylenes and plumbylenes catalyse the controlled polymerisation of L- and racemic lactide. The activity increases linearly according to Ge(II) ≪ Sn(II) ≪ Pb(II). The simple germylenes generate very sluggish catalysts, but the activity is significantly boosted if the heterobimetallic complex {LO(3)}Ge(N(SiMe3)2)·LiOTf is used instead. On the other hand, with 10-25 equiv. of iPrOH, the plumbylenes afford highly active binary catalysts, converting 1000 or 5000 equiv. of monomer at 60 °C within 3 or 45 min, respectively, in a controlled fashion.
稳定的锗（II）和铅（II）氨络合物{LO（i）}M（N（SiMe3）2）（M=Ge（II），Pb（II）），带有氨基（醚）苯并酚配体，可使用通用配体{LO（i）}H（i=1，NR2= N（（CH2）2OCH3）2；i=2，NR2=NEt2；i=3，NR2=氮杂-15-冠-5）和M（N（SiMe3）2）2前体制备。这些锗烯和铅烯以及{LO（3）}GeCl，{LO（3）}SnCl和同类{LO（4）}Sn（II）（N（SiMe3）2）的分子结构，其中NR2=氮杂-12-冠-4，已通过晶体学确定。所有配合物均为单体，具有 3 配位金属中心。苯并酚酸系统地作为 N^O（苯并酚）双齿配体，在这些情况下（对于{LO（1）}（-），{LO（3）}（-）和{LO（4）}（-）），金属和 O（侧臂）原子之间没有相互作用。对于每个家族，孤对电子基本上具有 ns（2）特征，并且价轨道的杂化很少，如果有的话。通过反应{LO（3）}M（N（SiMe3）2）和 LiOTf（M=Ge（II），Sn（II））制备了异双金属配合物{LO（3）}M（N（SiMe3）2）·LiOTf，其中Li（+）阳离子位于键合的冠醚内部。Li（+）（与三氟甲磺酸根阴离子紧密接触）在大环中的存在对二价四价元素的配位球没有影响。与 iPrOH 结合，酰胺锗烯，锡烯和铅烯催化 L-和外消旋丙交酯的受控聚合。活性根据 Ge（II）≪Sn（II）≪Pb（II）线性增加。简单的锗烯生成非常缓慢的催化剂，但是如果使用异双金属配合物{LO（3）}Ge（N（SiMe3）2）·LiOTf代替，则活性会大大提高。另一方面，在 10-25 当量的 iPrOH 存在下，铅烯提供了高活性的二元催化剂，在 60°C 下以 3 或 45 分钟的时间分别以可控方式转化 1000 或 5000 当量的单体。
