Syntheses, Characterization, and Molecular Mechanics Calculations of Optically Active Silatrane Derivatives

A series of optically active silatrane derivatives, [Si{N(CHRCH(2)O)(CH(2)CH(2)O)(2)}X] (R = Me, i-Pr; X = Ph, OMe) has been synthesized by the reaction of optically active triethanolamine derivatives with XSi(OMe)(3), and characterized by (1)H NMR, (13)C NMR, (29)Si NMR, and mass spectroscopy, and the structures of six compounds have been determined by X-ray analysis. Molecular mechanics methods have also been employed to obtain the energy-minimized structures. The (29)Si NMR chemical shifts and the lengths of Si-N determined by X-ray analysis are sensitive to the bulkiness of the substituent (R). The Si-X bond lengths (X: trans position to nitrogen) do not appreciably differ from one another. The MM2 calculations indicated that the substituent exists in the equatorial position, and the results are in agreement with those of X-ray analysis and (1)H NMR spectroscopy. Crystallographic data: [R = H; X = OMe], C(7)H(15)NO(4)Si, orthorhombic, Pna2(1), a = 13.407(1) ?, b = 8.761(2) ?, c = 8.191(1) ?, Z = 4; [R = Me; X = OMe], C(8)H(17)NO(4)Si, orthorhombic, P2(1)2(1)2(1), a = 10.110(3) ?, b = 11.083(2) ?, c = 9.474(2) ?, Z = 4; [R = i-Pr; X = OMe], C(10)H(21)NO(4)Si, monoclinic, P2(1), a = 8.481(1) ?, b = 7.805(1) ?, c = 10.218(2) ?, beta = 111.31(1) degrees, Z = 2; [R = Me; X = Ph], C(13)H(19)NO(3)Si, orthorhombic, P2(1)2(1)2(1), a = 8.813(1) ?, b = 11.137(2) ?, c = 13.757(1) ?, Z = 4; [R = i-Pr; X = Ph], C(15)H(23)NO(3)Si, orthorhombic, P2(1)2(1)2(1), a = 8.365(1) ?, b = 13.538(2) ?, c = 13.841(2) ?, Z = 4.