ChemInform Abstract: Synthesis and Some Properties of Si‐Substituted N‐(Dimethylsilylmethyl)lactams (III), (VI), (IX).

Pentacoordinated chlorosilanes with C,O-chelate ligands derived from N-methyl-N'-organosulfonyl-prolinamides*

“…We have already noted the high tendency of chlorosilanes 2 to undergo hydrolysis, which is markedly greater than for previously reported C,O-chelate pentacoordinated chlorosilanes [15,28]. Thus, recrystallization in the air led to the formation of silyloxonium chlorides [RSO 2 -Pro-N(Me)CH 2 SiMe 2 OH 2 ]Cl 5a-f.…”

“…The low-frequency shift of the absorption band corresponding to the NCO fragment in the IR spectra of chlorosilanes 2 (to ~1605 cm -1 ) relative to starting methylamides 1 and the presence of a second, less intense absorption band at ~1510 cm -1 indicate the (O→Si)-chelate structure of chlorosilanes 2 [15].…”

“…Rather efficient methods have been developed for the preparation of such monochlorosilanes [2,[12][13][14][15][16][17]. Furthermore, the synthesis of other derivatives of pentacoordinated silicon is carried out starting from monochlorosilanes.…”

“…The strength of the intramolecular O→Si coordination bond in these compounds varies in a rather broad range depending on the nature of the monodentate ligands at the silicon atom and substituents in the five-membered chelate ring [1][2][3][4][5][6][7][8][9][10][11]. Investigation of the structure features of pentacoordinated C,O-chelates with the SiC 3 OX coordination unit (X = Hal, OAlk, OAr, ½O, and Otf) [5,10,[12][13][14][15][16][17] allows using these compounds as models for studying hypervalence problem [1, 18,19] and modeling pathways for S N reactions at the silicon atom [1-5, 7-10, 20, 21].…”

Dynamic stereochemistry of hypervalent silicon, germanium and tin compounds containing amidomethyl C, O-chelating ligands

“…On going to the iodide and triflate 3 (M = Si) in CDCI3, the 8(29Si) signal continues to shift downfield (-22.7 and -5.3 ppm, respectively) and the coordination contributions A6 decrease (see Table 2). The transition from X = CI to substituents with higher nucleofugal capacities (Br, I, and Tf) results in characteristic changes in the 1500--1700 cm -l region of the IR spectra of these compounds (a broadened medium-intensity absorption band at 1620--1640 cm -i appears instead of the two medium-intensity bands at 1500--1520 cm -~ and the highly intense band at 1600--1610 cm -t) and also leads to a sharp increase in the electrical conductivities of their solutions in CH2CI2.to, 16,30 Thus, the whole set of data obtained by 29Si NMR and IR spectroscopy, X-ray diffraction analysis, and conductometry indicates that when substituent X is a relatively poor nucleofuge, the O--Si bond is the "coordination" bond (canonical structure A), whereas in compounds in which X is a good leaving group, Si--X becomes the "coordination" bond (canonical structure B) …”