1-[(4-Chlorobenzoyl)methyl]-4-(N,N-dimethylamino)pyridinium bromide sesquihydrate and 1-[(4-bromobenzoyl)methyl]-4-(N,N-dimethylamino)pyridinium bromide sesquihydrate.

The title compounds, C15H16ClN2O+.Br-.1.5H2O and C15H16BrN2O+.Br-.1.5H2O, are isomorphous. The benzene ring is oriented nearly normal to the pyridine ring in both compounds. The molecular packing is mainly influenced by intermolecular O-H...O and O-H...Br interactions, as well as weak intramolecular C-H...O interactions. The H2OBr- units form an extended water-bromide chain, with a bridging water molecule on a twofold axis.

Triimidosulfonic acid and organometallic triimidosulfonates: S(+)-N(-) versus S=N bonding.

Sulfonic acids RSO(2)OH and their metal salts MO(3)SR are versatile catalysts in large-scale industrial cyclization and polymerization processes. Isoelectronic replacement of the oxygen atoms by NR imido groups gives triimidosulfonic acid and triimidosulfonates. The salts form nonaggregated soluble molecules rather than infinite solid-state lattices such as their oxo analogues. In this paper, we present the synthesis and structure of the basic starting material MeS(N(t)Bu)(3)H (1), the metal complexes [Me(2)Al(N(t)Bu)(3)SMe] (2) and [Zn[(N(t)Bu)(3)SMe](2)] (3), and the mixed metal adduct [(thf)Li[(N(t)Bu)(3)SMe].ZnMe(2)] (4). The chelating coordination, rather than the tripodal coordination, cannot be attributed to steric effects of the S-bonded methyl group, as the less demanding Ph-C triple bond C-alkynyl substituent at sulfur in [(thf)(2)Li[(N(t)Bu)(3)SCCPh]] (5) causes the same conformation. S-N bond shortening to the pendant imido group has to be attributed to closed-shell electrostatic attraction rather than to S-N double bonding by valence expansion at the central sulfur atom. Coordination to an additional N-->Zn dative bond in 4 widens the bond length to values normally interpreted as S-N single bonds. We take this fact as experimental evidence that S-N bonding is predominantly governed by electrostatic interaction rather than by valence expansion employing d-orbitals. This was predicted by theoreticians more than a decade ago.

(MeLi)4(dem)1.5]infinity] and [(thf)3Li3M3[(NtBu)3S--how to reduce aggregation of parent methyllithium.

Organolithium compounds play the leading role among the organometallic reagents in synthesis and in industrial processes. Up to date industrial application of methyllithium is limited because it is only soluble in diethyl ether, which amplifies various hazards in large-scale processes. However, most reactions require polar solvents like diethyl ether or THF to disassemble parent organolithium oligomers. If classical bidentate donor solvents like TMEDA (TMEDA= N,N,N',N'tetramethyl-1,2-ethanediamine) or DME (DME=1,2-dimethoxyethane) are added to methyllithium, tetrameric units are linked to form polymeric arrays that suffer from reduced reactivity and/or solubility. In this paper we present two different approaches to tune methyllithium aggregation. In [[(MeLi)4(dem)1,5)infinity] (1; DEM = EtOCH2OEt, diethoxymethane) a polymeric architecture is maintained that forms microporous soluble aggregates as a result of the rigid bite of the methylene-bridged bidentate donor base DEM. Wide channels of 720 pm in diameter in the structure maintain full solubility as they are coated with lipophilic ethyl groups and filled with solvent. In compound 1 the long-range Li3CH3...Li interactions found in solid [[(MeLi)4]infinity] are maintained. A different approach was successful in the disassembly of the tetrameric architecture of [((MeLi)4]infinity]. In the reaction of dilithium triazasulfite both the parent [(MeLi)4] tetramer and the [[Li2[(NtBu)3S]]2] dimer disintegrate and recombine to give an MeLi monomer stabilized in the adduct complex [(thf)3Li3Me-[(NtBu)3S]] (2). One side of the Li3 triangle, often found in organolithium chemistry, is shielded by the tripodal triazasulfite, while the other face is mu3-capped by the methanide anion. This Li3 structural motif is also present in organolithium tetramers and hexamers. All single-crystal structures have been confirmed through solid-state NMR experiments to be the same as in the bulk powder material.

A new class of dianionic sulfur-ylides: alkylenediazasulfites.

The compounds [[(thf)Li2-[H2CS(NtBu)2]]2] (1) and [((thf)Li2[(Et)-(Me)CS(NtBu)2])2] (2) can be synthesized in a two-step reaction. Firstly addition of an alkyllithium to sulfur diimide gives the diazaalkylsulfinate [RS(NtBu)2] (R =Me, sBu). In a second step the alpha-carbon atom in R is metalated with one equivalent of methyllithium to give the S-ylides. This new class of compounds can be rationalized as sulfite analogues, in which two oxygen atoms are each isoelectronically replaced by a NtBu group and the remaining oxygen atom is replaced by a CR2 group. Similar to Corey's S-ylides (R2(O)S+-CR2) and Wittig's phosphonium ylides (R3P+ - -CR2), these molecules contain a positively charged sulfur atom next to a carbanionic center. Therefore nucleophilic addition reactions of the carbon atom are feasible. The reaction of a sulfur diimide with the anionic carbon center in [H2CS-(NtBu)2]2- gives the intermediate alkylbis(diazasulfinate) [(tBuN)2SCH2S(NtBu)2]2-. The acidity of the hydrogen atoms at the bridging CH2 group is high enough to give, upon deprotonation, the [(tBuN)2SCHS(NtBu)2]3- trianion in [[(thf)Li3[(tBuN)2SCHS(NtBu)2]]2] (3). In [(Et)(Me)CS(NtBu)2]2 the nucleophilic carbon atom is sterically hindered and transimidation instead of deprotonation is observed. In a complex redox process [(thf)6Li6S((NtBu)3S]2] is recovered. The two new classes of compounds broaden the rich coordination chemistry of the triazasulfites by the introduction of a hard carbon center.

The inverse podant [Li3(NBut)3S)]+ stabilises a single ethylene oxide OCH=CH2 anion as a high- and low-temperature polymorph of [(thf)3Li3(OCH=CH2)(NBut)3S)].

A single ethylene oxide anion derived from the ether cleavage reaction of thf with ButLi is stabilised by the inverse podant [Li3(NBut)3S)]+ to give a high- and a low-temperature polymorph with a considerable difference in conformation and packing.