The pyramidal Si2N-O skeleton of O-methyl-N,N-disilylhydroxylamine: An inherent phenomenon as confirmed by structural studies in different phases

Mitzel NW, Breuning E, Blake AJ, Robertson HE, Smart BA, Rankin DWH. The pyramidal Si2N-O skeleton of O-methyl-N,N-disilylhydroxylamine: An inherent phenomenon as confirmed by structural studies in different phases. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 1996;118(11):2664-2668.O-Methyl-N,N-disilylhydroxylamine, (H3Si)(2)NOCH3 (1), has been prepared by the reaction of bromosilane with O-methylhydroxylamine in the presence of 2,6-lutidine. The compound has been found to be reasonably stable at ambient temperature, but explodes if heated to 200 degrees C. 1 has been completely characterized by MS, HRMS, IR in the solid state and gas phase, and NMR spectra of the nuclei H-1, C-13, N-14/15, O-17, and Si-29. The NMR chemical shifts are compared with those of Si-methylated derivatives and with values obtained in high-level ab initio calculations. It has been concluded that there is close similarity between the structure in solution and the calculated one. A single crystal of 1 grown in situ and studied by X-ray diffraction is orthorhombic, space group P2(1)2(1)2(1), a = 6.3664(11) Angstrom, b = 8.488(2) Angstrom, c = 11.783(4) Angstrom, rho(calc) = 1.119 g cm(-1), Z = 4. Intermolecular Si ... O interactions (2.92 Angstrom) are found in the solid state structure leading to a zigzag type aggregation of the molecules. The gas phase structure of 1 has been determined by electron diffraction showing the molecule to have C-S symmetry. In both phases, the crystalline and the gas phase, the nitrogen atom configuration of 1 is pyramidal [<Sigma < (N) GED 351.8(12)degrees XRD 352.8(3)degrees], showing this to be an inherent feature of N-silylated hydroxylamines and not caused by packing farces. Most of the geometrical parameters are consistent for both phases showing that the intermolecular Si O interactions cause only minor structure distortions. The structural results are discussed in comparison with nb initio calculated geometries, and it is concluded that the exceptional nitrogen configuration is caused by repulsion between the nitrogen and oxygen lone pairs of electrons