Octahedral HSiCl₃ and HSiCl₂Me Adducts with Pyridines

Abstract

Stable solid adducts of substituted pyridines (Rpy) with HSiCl(3) and HSiCl(2)Me were prepared in high yields under aprotic and anaerobic conditions at room temperature. The octahedral complexes of HSiCl(3) underwent dismutation reactions in polar solvents. In contrast, the HSiCl(2)Me(Rpy)(2) adducts were not susceptible to dismutation under comparable conditions, but they tended to dissociate more easily because of the reduced Lewis acidity of HSiCl(2)Me relative to HSiCl(3). The bonding between silicon and its surrounding ligands is highly ionic, as can be seen from QTAIM and charge distribution analyses. (29)Si CP/MAS spectra in combination with quantum-chemical calculations show that the lowest shielding is along the Cl-Si-Cl axis. The other two components of the shielding tensor are oriented along the N-Si-N and H-Si-Cl/Me axes. It is known that many reactions of (hydrido)chlorosilanes are catalyzed by pyridine bases. Therefore, the results presented here provide a basis for better control of these reactions, especially chlorine substitution and hydrosilylation.

Ylenes in the MII→SiIV (M=Si, Ge, Sn) Coordination Mode

“…The relatively similar NCs of the ClN 4 -coordinated Si atoms are typical for hexacoordinate Si atoms in the formal oxidation state + IV, for example, between those calculated for HSiMeCl 2 (4-methylpyridine) 2 (+ 1.46) [21] and a Si compound with an O 2 N 2 F 2 Si skeleton (+ 2.27). [22] Compound 1, however, reveals some distinct differences to the others (2, 3, and 3 a).…”

Reduction of Imines with Trichlorosilane Catalyzed by Chiral Lewis Bases

“…the silicon of Cl 3 SiH [13,14]. The same effect can account for the very low enantioselectivity observed for the thiazole derivative 8d (entry 4).…”

Hexacoordinate Silicon Compounds with a Dianionic Tetradentate (N,N′,N′,N)-Chelating Ligand

“…Prior to reacting with the chlorosilanes to be chelated upon substitution of two Cl atoms [SiCl 4 , PhSiCl 3 , Ph 2 SiCl 2 , (Anis) 2 SiCl 2 and (4-Me 2 N-C 6 H 4 )PhSiCl 2 ], H 2 L was converted into its bis(trimethylsilyl) derivative (Me 3 Si) 2 L, as its conversion with further chlorosilanes (in a transsilylation reaction) produces chlorotrimethylsilane as a liquid and volatile byproduct, which allows for easy separation from the target complex. Whereas SiCl 4 , PhSiCl 3 , and Ph 2 SiCl 2 were commercially available, (Anis) 2 SiCl 2 and (4-Me 2 N-C 6 H 4 )PhSiCl 2 were prepared from SiCl 4 and PhSiCl 3 , respectively, and suitable Grignard reagents (see Experimental Section). [7][8][9][10][11]18,19,[73][74][75][76][77] chelators, we have now explored silicon coordination chemistry with a dianionic tetradentate (N,N′,N′,N) chelator.…”

“…Whereas the former preferentially bind to Si atoms that carry strongly electron withdrawing groups (e.g., formation of pyridine adducts of halosilanes, Scheme 1, A, [1][2][3]), the latter offer greater opportunities of creating five-and six-coordinate silicon compounds even in case of the absence of halides from the silicon coordination sphere (e.g., pentacoordinate silicon with SiC 5 coordination sphere, B [4][5][6]; and hexacoordinate silicon with a tetradentate chelator and two Si-CH 3 groups, C [7]). For various reasons, such as activation of Si-X bonds by silicon hypercoordination [8][9][10][11][12][13][14][15][16], exploring special electronic/optical properties arising from the higher coordination number of silicon in combination with selected ligands [17][18][19][20] or the aim of creating and exploring hitherto unusual Si coordination compounds, e.g., with transition metals [21][22][23][24][25][26][27][28][29] or very soft Lewis bases in their ligand sphere [30][31][32][33][34][35][36][37][38], silicon coordination chemistry continues to be an attractive research field, reflected by frequently published research articles [39][40]…”