Intramolecular Rearrangement of Organosilyl Groups in Silylamines:  A Combined Experimental−Theoretical Study

Abstract

The lithium salt of Me 3 CSiMe 2 NH 2 reacted with halosilanes to give the bis(silyl)amines 1-3, Me 3 -CSiMe 2 NHSiMe 2 R (1: R ) H, 2: R ) Me, 3: R ) CMe 3 ), which form lithium salts with BuLi. 4, the lithium salt of 1, crystallized as the trimer via the Li-N bond. Halosilanes reacted with lithiated bis-(silyl)amines to give tris(silyl)amines 5-9, RSiMe 2 N(SiMe 2 Hal)SiMe 2 R′ (5: R, R′ ) Me, Hal ) Cl; 6: R, R′ ) Me, Hal ) F; 7: R ) CMe 3 , R ) Me, Hal ) Cl; 8: R ) CMe 3 , R′ ) Me, Hal ) F; 9: R, R′ ) CMe 3 , Hal ) F). The ammonolysis of 5 and 7 led to the formation of the NH 2 -substituted compounds 10 and 11, RSiMe 2 N(SiMe 3 )SiMe 2 NH 2 (10: R ) Me, 11: R ) CMe 3 ). The fluorine-containing compounds (6, 8, 9) reacted with LiNH 2 to give the 1,3,5-trisila-2,4-diazanes 12-14, RSiMe 2 -NH-SiMe 2 -NH-SiMe 2 R′ (12: R, R′ ) Me; 13: R ) Me, R′ ) CMe 3 ; 14: R, R′ ) CMe 3 ). 10 and 12 as well as 11 and 13 are structural isomers. 12 and 13 are the result of a 1,3-silyl group migration in solution at low temperatures. Thermally the 1,3-silyl group migration occurred above 200 °C for 10 and at 130 °C using 11. Quantum-chemical calculations on the thermal isomerization process reveal a two-step mechanism, whereas the anionic isomerization occurs via a single transition state at lower temperatures. 10 and 12 form the same lithium salt (15), (Me 3 SiNH-SiMe 2 -NLi(THF)-SiMe 3 ) 2 . In the reaction of 15 with FSiMe 2 CMe 3 or of the lithiated compounds of 13 with ClSiMe 3 (Me 3 Si) 2 NSiMe 2 NHSiMe 2 CMe 3 (16) was obtained (eq 8). Starting from 15, the reaction again includes a 1,3-silyl group migration from one nitrogen to the other. In the reaction of lithiated 14 with ClSiMe 3 substitution occurred and 17 was obtained. Crystal structures of 4 and 15 are presented, and the mechanisms of the rearrangements are discussed.

Density functional study of the intramolecular proton transfer and conformations in hydroxyaminosilanethione

“…The optimized structures at the B3LYP/6-31G(d) level of theory gave good agreement with the available experimental data for related compounds [16][17][18]. Similar pentacoordinate silicon structures of 2Z and S2 have been reported previously [19][20][21]. The three-membered SiAOAN ring structural motif in S2 (SiAOAN angle 75.14°) has also been noted previously, in this case with an angle of 79.7° [21].…”

Group 1 Complexes of an (Amido-amino)silane and Their Use in the Synthesis of the Bi(III) Amide, Bi(Me2Si{NAr}{N(H)Ar})Cl2 (Ar = 2,6-i-Pr2C6H3)

“…A related cis-dimer to that found for II is present in the structure of compound III, where, in this example, the bulky SiMe 3 group at the amino-nitrogen atom prevents the formation of a second N−Li bond, giving a κ 1 -Ncoordination. 19 The final structural variant is the solvent-free structure of IV, in which the lithium atom forms a π-aryl interaction with a second molecule in the dimer. 20 In all cases I−IV, a simple approach was used in the synthesis and isolation of the crystalline complexes; viz.…”

Acyclic and Cyclic Silylaminohydrazines

“…Quantum-chemical calculations in our previous work on related silicon-nitrogen-containing compounds have shown that the N-Si bonds and the Li-N (TS) contacts are broken simultaneously in these reactions. The isomerization proceeds via a single dyotropic transition state (TS) [10].…”

“…This very constrained TS structure is possible due to the small size of the lithium cation [10,11]. In the TS the migrating silyl group and the lithium cation are coordinated to both nitrogen atoms.…”

“…In the meantime, silyl group migration has been applied to the synthesis of isomeric compounds, as well as to stabilizing elements in lower coordination numbers [3,6,7]. During the last years we studied migrations of hydrogen atoms and silyl groups in the chemistry of silazanes [8] and silyl hydrazines [6,9] both experimentally and by quantum-chemical calculations [10]. It was found that in such isomerization reactions hydrogen atoms can migrate from a carbon to a nitrogen atom [3,6] and from one nitrogen to another atom [6].…”