Chemistry and Structures of Hexakis(halogenomethyl)‐, Hexakis(azidomethyl)‐, and Hexakis(nitratomethyl)disiloxanes

Abstract

An investigation of the structures and chemistry of substituted hexamethyl disiloxanes ((XCH2)3Si)2O; X=F, Cl, Br, I, N3 , and ONO2) is reported. New synthetic routes to the precursor hexakis(chloromethyl)disiloxane are presented. The products with X=Cl, Br, I, and N3 were characterized by NMR, IR, and Raman spectroscopy. In addition, the single-crystal structures of the products with X=Cl, Br, and I are discussed in detail. The compounds with X=F and ONO2 were not obtained in their pure form; instead investigations of the decomposition products revealed their conversion into intermediates. Theoretical calculations of the gas-phase structures at the B3LYP/cc-pVDZ, B3LYP/3-21G, MP2/6-31G*, and MP2/3-21G levels of theory are used to explain the chemical and physical behavior of the compounds with X=Cl, Br, I, N3, and ONO2. A new decomposition pathway of hexakis(nitratomethyl)disiloxane is presented and is used to explain their remarkable instability. The energetic properties and values of the nitrate and azide derivatives were calculated at the CBS-4M level of theory by using the improved EXPLO5 computer code version 6.01.

Energetic Sila-Nitrocarbamates: Silicon Analogues of Neo-Pentane Derivatives

“…Another characteristic is the obtuse angle Si1−O1−Si1 I = 147.6°, which is in the range of other disiloxane structures of disilylether (144.1°), hexafluorodisiloxane (156°), and hexakis-(chloromethyl) disiloxane (161.9°). 10 In comparison with the monosubstituted nitrocarbamate 1b, the nitrocarbamate units of the disiloxane 5 deviate significantly from planarity, as is the case for the bisnitrocarbamate 2b. Both nitrocarbamate units are located in antiperiplanar fashion to each other to avoid sterical hindrance.…”

“…The atom distances Si1–O1 and Si1–O1 I differ with 1.61 and 1.70 Å, respectively, and lie between a Si–O single (1.77 Å) and double (1.54 Å) bond. Another characteristic is the obtuse angle Si1–O1–Si1 I = 147.6°, which is in the range of other disiloxane structures of disilylether (144.1°), hexafluorodisiloxane (156°), and hexakis­(chloromethyl) disiloxane (161.9°) …”

“…29 Si NMR (CDCl 3 ): δ = 0.3. Raman (800 mW): 2961 (40), 2902 (100), 1691 (8), 1440 (2), 1418 (9), 1114 (5), 1074 (10), 907 (10), 703 (10), 604 (77), 510 (5), 317 (12) cm −1 . IR: 3439 (w), 3330 (w), 3266 (w), 3209 (w), 2957 (w), 2905 (w), 1741 (w), 1687 (s), 1608 (m), 1436 (w), 1375 (s), 1265 (w), 1250 (m), 1219 (w), 1121 (w), 1061 (s), 904 (w), 841 (s), 785 (m), 719 (w), 701 (w) cm Nitrocarbamoylmethyl Trimethylsilane (1b).…”

“…29 Si NMR (DMSO-D 6 ): δ = −0.6; −0.4 (acetone-D 6 ). Raman (800 mW): 2970 (29), 2944 (39), 2905 (74), 1735 (38), 1623 (24), 1423 (19), 1382 (36), 1332 (13), 1006 (51), 897 (38), 750 (12), 707 (10), 677 (12), 604 (100), 464 (43), 416 (12), 309 (12), 230 (29) cm −1 . IR: 3224 (w), 3171 (w), 3124 (w), 3011 (w), 2819 (vw) Tris(carbamoylmethyl) Methylsilane (3a).…”

“…29 Si NMR (DMSO-D 6 ): δ = −5.5. Raman (800 mW): 3261 (3), 3200 (9), 2973 (19), 2954 (3), 2945 (20), 2910 (100), 2861 (8), 1695 (20), 1633 (6), 1633 (6), 1444 (26), 1306 (12), 1265 (8), 1217 (14), 1121 (20), 1083 (10), 1071 (6), 1015 (9), 904 (40), 835 (30), 768 (5), 711 (10), 647 (4), 610 (41), 537 (6), 501 (19), 367 (12), 341 (3), 317 (9), 278 (7) Tris(nitrocarbamoylmethyl) Methylsilane (3b). Anhydrous nitric acid (>99.5%, 1 mL) was slowly dropped into concentrated sulfuric acid (1 mL) at 0 °C.…”