1825-65-6

A molybdenum-dinitrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo(N2)2(depf)2] (depf = 1,1′-bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N2) into silylamine (N(SiMe3) 3), which can be readily converted into NH3 by acid treatment. The conversion has been achieved in the presence of Me 3SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe3)3 generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai's group for mononuclear molybdenum complexes having monophosphine coligands [J. Am. Chem. Soc.1989, 111, 1939]. Density functional theory (DFT) calculations have been performed to figure out the mechanism of the catalytic N2 conversion. On the basis of some pieces of experimental information, SiMe3 radical is assumed to serve as an active species in the catalytic cycle. Calculated results also support that SiMe3 radical is capable of working as an active species. The formation of five-coordinate intermediates, in which one of the N2 ligands or one of the Mo-P bonds is dissociated, is essential in an early stage of the N2 conversion. The SiMe 3 addition to a "hydrazido(2-)" intermediate having the NN(SiMe3)2 group will give a "hydrazido(1-)" intermediate having the (Me3Si)NN(SiMe3)2 group rather than a pair of a nitrido (-N) intermediate and N(SiMe3) 3. The N(SiMe3)3 generation would not occur at the Mo center but proceed after the (Me3Si)NN(SiMe3) 2 group is released from the Mo center. The flexibility of the Mo-P bond between Mo and depf would play a vital role in the high catalysis of the Mo-Fe complex.

The catalytic activity of titanium alkoxy derivatives of various structures in heterofunctional condensation of alkoxy- and acyloxysilanes was studied by the kinetic method. The correlation between the catalytic activity and chemical transformations of the titanium compounds in the course of the reaction was demonstrated.

Acetophenone dibutyl acetal reacts with dipropylchloroborane or trimethylchlorosilane, yielding 1,3,5-triphenylbenzene.The reaction is also successful in the presence of catalytic amounts of these electrophiles.

Two methods for the synthesis of isolable methyleniminium salts and amidinium salts are presented.In the first case carbonyl compounds A are treated with a mixture of (dialkylamino)trimethylsilane (12) and chlorotrimethylsilane (13) or 12 and trimethylsilyl triflate (14) leading to the iminium chlorides F or iminium triflates G, respectively.With 12/13 the preparation of F is limited to non-enolizable aldehydes and dimethylformamide (10), while 12/14 enables the preparation of G, e.g. 23a-25a, 27a, also with ketones and with substituted amides.The second procedure is based on the treatment of α-chloro ethers L with 12.Both methods afford the Mannich reagent 16a in high yields.By reaction of the α-chloro ether 35 with 12 in diethyl ether the vinylogous Viehe salts 36a-c, e become available for the first time.The reaction pathways are discussed. - Key Words: Methyleniminium salts, preparation, mechanisms of formation / (Dialkylamino)trimethylsilanes / Ethers, α-chloro / Viehe salts, vinylogous

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The reactions of bis(trimethylsilyl)peroxide with alkyl, vinyl, alkynyl, aromatic and heteroaromatic anions are described.Depending on the reaction conditions, the trimethylsilyloxy derivatives can be obtained alone or together with the corresponding trimethylsilyl derivatives, which is sometimes the major product.Enolates, generated using magnesium diisopropylamide give the corresponding hydroxycarbonyl compounds in good yields.An attempt to rationalise the above results is given, emphasising the wide use of bis(trimethylsilyl)peroxide in organic synthesis as an electrophilic hydroxylation reagent.

Alkanol-alkoxide negative ions 1O...H...OR2>(-) react with alkoxysilanes Me3SiOR3 to produce both 1O(-)> and 2O(-)> ions of trigonal bipyramidal geometry.When R1 2 and either R1 or R2 >= Pr, the four-center reaction 1O...H...OR2>(-) + Me3SiOR3 -> 2O...H...OR3>(-) + Me3SiOR1 is observed.Addition of 1O...H...OR2>(-) in the reverse direction is not detected.Analogous reactions do not occur between Me3SiX and 1O...H...OR2>(-) when X = F, NHR, NR2, SiMe3, alkyl, allyl, propargyl, benzyl, or aryl, but 1O...H...X>(-) ions of small abundance are formed when X = HO, OCOMe, OCN, and SR.Cyclic ethers react with alkanol-alkoxyde negative ions by reaction (i;n = 2-4).

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