Synthesis, Characterization, and Structures of Divalent Europium and Ytterbium N,N-Dimethylaminodiboranates

Treatment of the trichlorides EuCl3 and YbCl3 with Na(H3BNMe2BH3) in tetrahydrofuran (THF) results in a reduction to the corresponding divalent europium and ytterbium N,N-dimethylaminodiboranate (DMADB) complexes Eu(H3BNMe2BH3)2(THF)2 (1) and Yb(H3BNMe2BH3)2(THF)2 (2), which can be separated from trivalent Ln(H3BNMe2BH3)3(THF) byproducts by extraction and crystallization from pentane. No other lanthanide trihalides react with Na(H3BNMe2BH3) to afford divalent products. Compounds 1 and 2 can also be prepared from the divalent lanthanide iodides EuI2 and YbI2 in higher yield and without the need to separate them from trivalent species. Treatment of 1 and 2 with an excess of 1,2-dimethoxyethane (DME) in pentane affords the new species Eu(H3BNMe2BH3)2(DME)2 (3) and Yb(H3BNMe2BH3)2(DME) (4). Compound 1 is dinuclear: each metal center is bound to two chelating DMADB ligands, one of which also bridges to the other metal. Overall, the coordination geometry about each Eu atom can be described as a distorted pentagonal bipyramid, with five B atoms from the DMADB ligands occupying the equatorial sites and two THF molecules occupying the axial sites. Unlike 1, compound 2 is monomeric owing to the smaller radius of YbII versus EuII; the B and O atoms describe a distorted cis octahedron. The Eu(DME) complex 3 is also monomeric; both DMADB ligands and both DME molecules chelate to the metal center. The four B atoms and the four O atoms describe a distorted square antiprism, with the O atoms occupying one square face and the B atoms occupying the other. In addition to X-ray crystallographic studies, IR, NMR, and mass spectrometric data are reported for all four new compounds.

以四氢呋喃（THF）为溶剂，将三氯化铕（EuCl3）和三氯化镱（YbCl3）与钠三苯基膦基硼烷（Na(H3BNMe2BH3)）反应，可将其还原为相应的二价铕和镱N,N-二甲基氨基二硼烷（DMADB）配合物Eu(H3BNMe2BH3)2(THF)2（1）和Yb(H3BNMe2BH3)2(THF)2（2），这些配合物可通过萃取和从戊烷中结晶的方式与三价镧系元素N,N-二甲基氨基二硼烷（Ln(H3BNMe2BH3)3(THF)）副产物分离。除镧系三卤化物外，其他镧系三卤化物均不与Na(H3BNMe2BH3)反应生成二价产物。化合物1和2还可以从二价镧系元素碘化物EuI2和YbI2中制备，且产率更高，且无需从三价物种中分离。将1和2与过量的1,2-二甲氧基乙烷（DME）在戊烷中处理，可得到新的物种Eu(H3BNMe2BH3)2(DME)2（3）和Yb(H3BNMe2BH3)2(DME)（4）。化合物1为双核结构：每个金属中心被两个螯合的DMADB配体所配位，其中一个配体还桥接至另一个金属中心。总体而言，每个铕原子周围的配位几何结构可描述为畸变的五角双锥，其中来自DMADB配体的五个硼原子占据赤道位置，而两个THF分子占据轴向位置。与1不同，2为单核结构，这是由于镱(II)的半径小于铕(II)的半径；硼和氧原子构成畸变的顺式八面体。铕(DME)配合物3也是单核结构；两个DMADB配体和两个DME分子均螯合至金属中心。四个硼原子和四个氧原子构成畸变的正方形反四面体，其中氧原子占据一个正方形面，硼原子占据另一个面。此外，对这四种新的化合物进行了X射线晶体学、红外光谱、核磁共振和质谱数据的研究。