6-(1-Methylethyl)-12-phenyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azasilocine

The title compound, C23H25NSi, has an eight-membered silicon-containing heterocyclic ring with an intramolecular N⋯Si close contact, the transannular distance of which is 2.6294 (18) Å. The resulting geometry about the Si atom is distorted trigonal-bypyramidal, with the N and H atoms occupying apical sites. The dihedral angle between the aromatic rings fused to the eight-membered ring is 63.27 (7)°.

The title compound, C 23 H 25 NSi, has an eight-membered silicon-containing heterocyclic ring with an intramolecular NÁ Á ÁSi close contact, the transannular distance of which is 2.6294 (18) Å . The resulting geometry about the Si atom is distorted trigonal-bypyramidal, with the N and H atoms occupying apical sites. The dihedral angle between the aromatic rings fused to the eight-membered ring is 63.27 (7) .

Comment
Highly coordinated hydrosilanes have been of great interest for their unique structures and reactivities. It has been known that, in highly coordinated monohydrosilanes, the Si-H bond has high affinity for equatorial position (Brellère et al., 1986) and there are only a few examples with the Si-H bond at the apical position (Woning & Verkade, 1991). A dibenz[c,f][1,5]azasilocine framework has been utilized for the synthesis of various highly coordinated silicon compounds (Paton et al., 1977;Carré et al., 1997;Yoshida et al., 2006). Recently, we reported the synthesis and structural characterization of a pentacoordinated monohydrosilane bearing this molecular framework with the apical Si-H bond (Saruhashi et al., 2001). As a further investigation of this work, the crystal structure of the title new hydrosilane is reported.
The title compound was synthesized by the reaction of N,N-bis(2-bromobenzyl)isopropylamine (Carré et al., 1997) with n-butyllithium followed by treatment with phenylsilane. The molecular structure of the title compound is shown in Fig. 1. It was found that the geometry around the silicon atom is that of a distorted trigonal bypyramid with the sum of the equatorial C-Si-C bond angles of 346.3°. The SiH hydrogen atom occupies the apical site in spite of its lower apicophilicity than that of a phenyl group, which is similar to the related N-butyl compound we previously reported (Saruhashi et al., 2001).
The Si···N transannular distance is 2.6294 (18) Å, which is slightly longer than that of the N-butyl derivative [2.516 (2) Å] probably because of the steric repulsion between the isopropyl group and the phenyl ring.

Experimental
A solution of n-butyllithium in hexane (1.6 M; 4.2 ml, 6.7 mmol) was added dropwise to a solution of N,N-bis(2bromobenzyl)isopropylamine (1.25 g, 3.16 mmol) in ether (3 ml) at 233 K. The solution was stirred at the same temperature for 30 min and then allowed to warm to room temperature. After stirring for additional 2 h, the solution was cooled to 233 K, and a solution of phenylsilane (345 mg, 3.19 mmol) in ether (2 ml) was added dropwise. The mixture was allowed to warm to room temperature, and stirred overnight. After addition of water, the mixture was extracted with ether, and the organic layer was dried over anhydrous magnesium sulfate. After filtration and removal of the solvent, the residue was purified by gel permeation liquid chromatography (eluting with chloroform) and then recrystallization from hexane to give the title compound (101 mg, 0.295 mmol, 9.3%) as colorless crystals.

Refinement
The H atom of the SiH group was found in a difference Fourier map and refined isotropically, while the C-bound H atoms were treated as riding, with C-H = 0.95-0.99 Å, and with U iso (H) = 1.2 (1.5 for methyl groups) times U eq (C). The methyl groups were allowed to rotate freely about the C-C bond. Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids (arbitrary spheres for H atoms).   (2)