Sulfur-Induced Pentacoordination in Cyclic Silanes¹

Abstract

Reaction of dichlorosilanes with diols in the presence of Et3N in toluene solution gave the monocyclic silanes S[(t-Bu)2C6H2O]2Si(Ph)Me (1), S[(t-Bu)2C6H2O]2SiPh2 (2), S[t-BuMeC6H2O]2Si(Ph)CHCH2 (3), and S[Me2C6H2O]2SiPh2 (4). X-ray structural analysis revealed that the silanes 1−3 exhibited varying degrees of sulfur−silicon donor coordination, giving geometries intermediate between a tetrahedron and a trigonal bipyramid. The eight-membered ring, common to 1−3, which contained the sulfur atom as a bridge between two aryl groups, resided in a syn or boatlike conformation. For the cyclic silane 4 having the same type of ring composition, X-ray analysis showed no sulfur−silicon interaction, and the ring in this case was in an anti or chairlike conformation. Similar to that observed with pentaoxyphosphoranes possessing the same type of sulfur-containing eight-membered ring, sulfur donor ability increased with an increase in alkyl substitution on the ring aryl components (t-Bu > Me). Sulfur coordination in the phosphorus compounds gave geometries along a coordinate from square pyramidal to octahedral. Retention of the solid state structures in solution is indicated by comparison of 29Si NMR data on 1−4 with solution state and solid state 29Si NMR data on related silanes. The ability of the sulfur atom of reduced electronegativity to promote silanes to a higher coordinate state shows that hypervalency is readily accessible for silicon. Silane 1 crystallizes in the monoclinic space group P21/n with a = 10.133(3) Å, b = 20.839(4) Å, c = 16.181(3) Å, β = 99.47(2)°, and Z = 4. Silane 2 crystallizes in the monoclinic space group Cc with a = 10.006(2) Å, b = 42.478(6) Å, c = 17.917(4) Å, β = 99.25(1)°, and Z = 8. Silane 3 crystallizes in the orthorhombic space group Pna21 with a = 20.735(2) Å, b = 12.724(1) Å, c = 10.387(1) Å, and Z = 4. Silane 4 crystallizes in the monoclinic space group P21/c with a = 10.786(2) Å, b = 26.053(7) Å, c = 8.876(1) Å, β = 100.57(1)°, and Z = 4. The final conventional unweighted residuals are 0.059 (1), 0.035 (2), 0.027 (3), and 0.050 (4).

Organogallium complexes incorporating tridentate thioetherbiphenolate ligands 2,2′-thiobis(4,6-di-tert-butylphenolate), Stdiol and 2,2′-thiobis(4,6-dimethylphenolate), Smdiol

“…We thus sought to fulfil this gap by employing substituted 2,2 0 -thiobis(4,6-dialkylphenolate) dianions as tridentate ligands and systematically explore the chemistry and the potential catalytic activity of their group 13 metal compounds. Thioetherbisphenol ligands had previously been used to form phosphorous [26 -31], silicon [32], germanium [33] and titanium [34,35] compounds demonstrating that the coordination ability of the ligand can be tuned by the choice of substituients. Moreover, it has been demonstrated that replacement of the methylene bridge in bisphenolate titanium systems by a sulphur atom results in the improvement of the activity in olefin polymerization reactions [34 -38].…”

Theoretical Conformational Analysis of Cyclic Organophosphorus and Organosilicon Compounds

“…17 The twisted boat form of 22 is preferred according to the quantum chemical calculations; the exocyclic phenyl substituent is axial, and the Si C Ph and C C bonds eclipse each other. The presence of exaltation between the experimental and calculated dipole moments of silocin 22 (Table 3) indicates the feasibility of the transannular interaction S→Si in this compound.…”

Metallocanes of group 14 elements. 1. Derivatives of silicon and germanium. (Review)

“…A series of compounds 6a-f and 7, in which the eight-membered ring contains a sulfur atom capable of acting as a donor of electron density, have been studied by X-ray crystallographic analysis [34][35][36]. Analysis of the structural data showed the existence of transannular Si←S interaction of various strengths (2.98-3.63 Å, sum of the van der Waals radii of the Si and S atoms 3.90 Å) in these derivatives.…”

“…The reaction mixture was kept at 25-55°C, and triethylamine was used to combine with the hydrogen chloride that formed [34][35][36][37].…”