Homoleptic Divalent Dialkyl Lanthanide-Catalyzed Cross-Dehydrocoupling of Silanes and Amines

作者：Pindwal Aradhana; Ellern Arkady; Sadow Aaron D^*

来源：Organometallics, 2016, 35(11): 1674-1683.

DOI：10.1021/acs.organomet.6b00138

The rare-earth bis(alkyl) compound Sm{C(SiHMe2)(3)}(2)THF2 (1b) is prepared by the reaction of samarium(II) iodide and 2 equiv of KC(SiHMe2)(3). This synthesis is similar to that of previously reported Yb{C(SiHMe2)(3)}2THF(2) (la), and compounds la,b are isostructural. Reactions of lb and 1 or 2 equiv of B(C6F5)(3) afford SmC(SiHMe2)(3)HB(C6F5)(3)THF2 (2b) or Sm{HB(C6F5)(3)}2THF(2) (3b), respectively, and 1,3-disilacyclobutane {Me2Si-C(SiHMe2)(2)}(2) as a byproduct. Bands from 2300 to 2400 cm(-1) assigned to vBH in the IR spectra and highly paramagnetically shifted signals in the 1113 NMR spectra of 2b and 3b provided evidence for Sm-coordinated HB(C6F5)(3). Compounds la,b react with the bulky N-heterocyclic carbene (NHC) 1,3-di-tert-butylimidazol-2-ylidene (ImtBu) to displace both THF ligands and give three-coordinate monoadducts Ln{C(SiHMe2)(3)}(2)]mtBu (Ln = Yb (4a), Sm (4b)). Complexes 4a,b catalyze cross-dehydrocoupling of organosilanes with primary and secondary amines at room temperature to give silazanes and 112, whereas la,b are not effective catalysts under these conditions. Second-order plots of In{[Et2NH]/[Ph2SiH2]} vs time for 4a-catalyzed dehydrocoupling are linear and indicate first-order dependences on silane and amine concentrations. However, changes in the experimental rate law with increased silane concentration or decreased amine concentration reveal inhibition by silane. In addition, excess ImtBu or THF inhibit the reaction rate. These data, along with the structures of 4a,b, suggest that the bulky carbene favors low coordination numbers, which is important for accessing the catalytically active species.

• 出版日期2016-6-13