Supramolecular structure in s-block metal complexes of sulfonated monoazo dyes: discrepant packing and bonding behavior of ortho-sulfonated azo dyes.

The first solid-state structures of ortho-sulfonated monoazo dyestuffs are reported and compared to those of their para- and meta-sulfonated analogues. The structures of the 16 Na, K, Cs, Mg, Ca, Sr, and Ba ortho-sulfonated salts are found to have fewer M-O(3)S bonds than their isomeric equivalents and this in turn means that the metal type is no longer the prime indicator of which structural type will be adopted. M-O(3)S bonds are replaced by M-OH(2), M-HOR and M-pi interactions, apparently for steric reasons. As well as new bonding motifs, the changed dye shape also leads to new packing motifs. The simple organic/inorganic layering ubiquitous to the para- and meta-sulfonated dye salt structures is replaced by variations (organic bilayers, inorganic channels), each of which correlates with a different degree of molecular planarity in the sulfonated azo dye anion.

Structurally defined potassium-mediated zincation of pyridine and 4-R-substituted pyridines (R = Et, iPr, tBu, Ph, and Me2N) by using dialkyl-TMP-zincate bases.

Two potassium-dialkyl-TMP-zincate bases [(pmdeta)K(mu-Et)(mu-tmp)Zn(Et)] (1) (PMDETA = N,N,N',N'',N''-pentamethyldiethylenetriamine, TMP = 2,2,6,6-tetramethylpiperidide), and [(pmdeta)K(mu-nBu)(mu-tmp)Zn(nBu)] (2), have been synthesized by a simple co-complexation procedure. Treatment of 1 with a series of substituted 4-R-pyridines (R = Me(2)N, H, Et, iPr, tBu, and Ph) gave 2-zincated products of the general formula [{2-Zn(Et)(2)-mu-4-R-C(5)H(3)N}(2)2{K(pmdeta)}] (3-8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51%, respectively; the treatment of 2 with 4-tBu-pyridine gave [{2-Zn(nBu)(2)-mu-4-tBu-C(5)H(3)N}(2)2{K(pmdeta)}] (9) in an isolated crystalline yield of 58%. Single-crystal X-ray crystallographic and NMR spectroscopic characterization of 3-9 revealed a novel structural motif consisting of a dianionic dihydroanthracene-like tricyclic ring system with a central diazadicarbadizinca (ZnCN)(2) ring, face-capped on either side by PMDETA-wrapped K(+) cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium-zincate base acts as an amido transfer agent with a subsequent ligand-exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4-coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl-zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of Zn-N bonds for efficient zincation.

Structural variations within group 1 (Li-Cs)+ (2,2,6,6-tetramethyl-1-piperidinyloxy)- complexes made via metallic reduction of the nitroxyl radical.

Treatment of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) with a group 1 metal (Li, Na, K, Rb, or Cs), resulted in the reduction of this important radical to the TEMPO(-) anion--the first examples of elemental-metal single electron reduction of the radical to its anionic form. The synthesis and characterization of seven alkali metal TEMPO(-) complexes are reported. A variety of structural motifs are encountered depending on the choice of metal and/or solvent. (THF)(2) x [Li(+)(TEMPO(-))](4) 1 crystallized from THF as a cyclic (Li(4)O(4)) molecule. Two Li centers are stabilized by coordination to a THF molecule; the others by intramolecular coordination to N(TEMPO) atoms. [(THF) x Na(+)(TEMPO(-))](4) 2 exists as a distorted cubane where each Na center is coordinated to a THF molecule. No appreciable Na-N(TEMPO) coordination is observed. [(THF)(2) x Na(+)(3)(TEMPO(-))(2)(OH)](2) 3 was serendipitously prepared and exists as a distorted bis(cubane). It is envisaged that 3 is formed from 2 by insertion of a (Na-OH)(2) double bridge into its framework. [Na(+)(4)(mu(3)-TEMPO(-))(2)(mu(2)-TEMPO(-))(2)(TMEDA)(2)] 4, adopts a four-runged ladder structure, whereby the two outer Na centers are coordinated to TMEDA, in addition to two mu(2)-O and a N atom. The inner metal atoms are bound to three mu(3)-O atoms and a N atom. [(THF) x K(+)(TEMPO(-))](4) 5 resembles the motif found for 2; however, presumably because of the larger size of the metal, K-N(TEMPO) interactions are present in 5. The asymmetric unit of [(TMEDA) x Rb(+)(2)(TEMPO(-))(2)](2) 6 comprises a Rb(4)O(4) cubane with half a molecule of TMEDA coordinated to each metal. From a supramolecular perspective, 6 exists as a polymeric array of cubane units connected by TMEDA bridges. Completing the series, [Cs(+)(TEMPO)](infinity) 7 crystallizes from hexane to form a donor-free polymeric complex. Complexes 1, 2, and 4-7 are soluble in D(8)-THF solution, and their NMR spectra are reported. The solution structures in donor solvent appear virtually identical.

Donor-dictated interlocking co-complexation reactions of LiNHDipp with dimethylzinc: synthesis and structures of new methyl(amido)zincates.

A systematic study of the interlocking co-complexation reactions between the primary lithium amide LiNHDipp (Dipp = 2,6-diisopropylphenyl) and dimethylzinc in the presence of different donor ligands is presented which concludes that the final outcome of these reactions is largely dictated by the type of structure that is formed when the donor is coordinated to the lithium amide. When chelating diamine TMEDA (N,N,N',N'-tetramethylethylenediamine) is employed [{Li(2)(NHDipp)(2)(TMEDA)}(infinity)] (1) is obtained, where Li(2)N(2) rings are connected by TMEDA bridges generating a polymeric chain arrangement which does not form a co-complex with Me(2)Zn even in the presence of an excess of TMEDA. The tridentate ligand PMDETA (N,N,N',N'',N''-pentamethyldiethylenetriamine) when reacted with LiNHDipp forms monomeric [(PMDETA)Li(NHDipp)](4) which successfully forms a mixed-metal co-complex with Me(2)Zn affording dialkyl(amido)zincate [(PMDETA)LiZn(NHDipp)(Me)(2)] (2). When the co-complexation reaction is carried out in the presence of monodentate tetrahydrofuran (THF), zincate [(THF)(3)LiZn(NHDipp)(Me)(2)] (3) is obtained which was found to partially decompose in hexane solution after long periods of time at room temperature (2 weeks) to afford the unprecedented "zinc-rich" zincate [(THF)(3)LiZn(2)(Me)(3)(NHDipp)(2)] (5). This compound presents a unique structure in the solid state previously unknown in organozincate chemistry with a trinuclear Li...Zn...Zn chain arrangement where the metals are connected by only two amido bridges and therefore both zinc centers exhibit trigonal planar geometries. 5 can be prepared in good yields by the rational reaction of LiNHDipp with a 2:1:3 mixture of Me(2)Zn, NH(2)Dipp and THF. The different solid-state structural motifs of compounds 1, 2, 4, and 5 have been revealed by X-ray crystallographic studies. Multinuclear NMR ((1)H, (13)C and (7)Li) spectroscopic data recorded in C(6)D(6) solution are also reported for compounds 1-6. Mixed-metal compounds 2 and 5 constitute the first examples of crystallographically characterized alkyl(amido)zincates containing a primary amide.

Synthetic and structural insights into the zincation of toluene: direct synergic ring metallation versus indirect nonsynergic lateral metallation.

Toluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)Na(tBu)(tmp)Zn(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)Na(C(6)H(4)Me)(tmp)Zn(tBu)] (2) (TMEDA = N,N,N',N'-tetramethylethylenediamine, TMP = 2,2,6,6-tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed-metal base. The crystal structures of both regioisomers have been elucidated by using X-ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent sigma bond; whereas sodium adopts a perpendicular disposition, pi-engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl-based zincate [(tmeda)(2)Na(CH(2)Ph)Zn(tBu)(2)] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed-metal compound by co-complexation with tBu(2)Zn. Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.

A structural and computational study of synthetically important alkali-metal/tetramethylpiperidide (TMP) amine solvates.

Two heavy alkali-metal salts of the sterically demanding amine, 2,2,6,6-tetramethylpiperidine (TMPH), have been prepared using different methodologies. Complex 1, [((tmeda)Na(tmp))2] (TMEDA=N,N, N',N'-tetramethylethylenediamine), can be synthesized by a deprotonative route. This is achieved by reacting butylsodium with TMPH in the presence of excess TMEDA in hexane. The potassium congener [((tmeda)K(tmp))2] (2), can be prepared by treating KTMP (made using a metathesis reaction between LiTMP and potassium tert-butoxide) with an excess of TMEDA in hexane. In the solid state, 1 and 2 are essentially isostructural. They are discretely dimeric and their framework consists of a four-membered M-N-M-N ring (M=Na or K, N=TMP). Due to the high steric demand of the TMP ligand, the TMEDA molecules bind to the metal centers in an asymmetric manner. In 2, each of the coordination spheres of the metals is completed by an agostic K...CH3(TMP) interaction. DFT calculations at the B3 LYP/6-311G** level give an insight into why 1 and 2 adopt dramatically different structures from their previously reported, "open-dimeric", lithium counterpart. The theoretical work also focuses on the TMEDA-free parent amide complexes and reveals that the energy difference for the formation of [(M(tmp))x] (in which, M=Li or Na, x=3 or 4; and M=K, x=2, 3 or 4) are small.

Structurally-defined potassium-mediated regioselective zincation of amino- and alkoxy-substituted pyridines.

The new synergic base [PMDETA.K(TMP)(Et)Zn(Et)] selectively zincates 4-(dimethylamino)pyridine at the 2-position and 4-methoxypyridine at the 3-position, to afford bimetallic potassium pyridylzinc complexes each displaying a novel, but remarkably different, structure.

Synthesis and characterisation of new bimetallic alkali metal-magnesium mixed diisopropylamide-acetylides: structural variations in bimetallic lithium- and sodium-heteroleptic magnesiates.

The reactivity of the Brønsted basic mixed-metal tris-amide compounds of empirical formula [MMg(N(i)Pr2)3] [where M = Li (1), Na (2)] towards phenylacetylene (HC[triple bond, length as m-dash]CPh) has been investigated and has led to the synthesis of a series of mixed-metal acetylido-amido-magnesiates. Thus, 1 and 2 molar equivalents of the alkyne with [MMg(N(i)Pr2)3] produce heteroanionic bis(amido)-mono(acetylido) [LiMg(N(i)Pr2)2(C[triple bond, length as m-dash]CPh)]2 (3) and mono(amido)-bis(acetylido) [(TMEDA) x Na(C[triple bond, length as m-dash]CPh)2Mg(N(i)Pr2)](2) (4) (TMEDA = N,N,N',N'-tetramethylethylenediamine) respectively. X-Ray crystallographic studies reveal that the new compounds adopt a different structural motif. Complex can be defined as an inverse crown structure, having a cationic eight-atom [(NaNMgN)2]2+ ring which hosts in its core two acetylido ligands. On the other hand, adopts a tetranuclear NaMgMgNa near-linear chain arrangement, held together by acetylido and amido bridges. The metal coordination geometries in both structures are distorted tetrahedral, and the sodium cations at the end of the mixed-metal chain carry terminal chelating TMEDA ligands. 1H and 13C NMR spectral data recorded in C6D6 solutions are also reported for and , and are consistent with the solid-state structures being retained in solution.

Synthetic and structural investigations of alkali metal diamine bis(phenolate) complexes.

Two lithium and one sodium diamine bis(phenolate) complexes have been prepared and characterised by X-ray crystallography and NMR spectroscopy. Two parent diamine bis(phenol) ligands were utilised in the study (1-H2 and 2-H2). Dimeric (1-Li2)(2) was prepared by treating 1-H2 with two molar equivalents of n-butyllithium in hydrocarbon solvent. It adopts a ladder-like structure in the solid state, which appears to deaggregate in C6D6 solution. The monomeric (hence, dinuclear) TMEDA-solvated species [2-Li(2).(TMEDA)] has two chemically unique Li atoms in the solid state and is prepared by reacting 2-H2 with two molar equivalents of n-butyllithium in hydrocarbon solvent, in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA). Finally, the dimeric sodium-based [2-Na(2) x (OEt2](2) was prepared by reacting 1-H2 with two molar equivalents of freshly prepared n-butylsodium in a hydrocarbon-diethyl ether medium. The complex adopts a Na4O4) cuboidal structure in the solid state, which appears to remain intact in C6D6 solution.

Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates.

Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] ( 4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N,N,N-pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(mu-Me)Zn(HMDS)Me] ( 5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] ( 6) and [(tBuCN)Li(HMDS)] ( 7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy.

Isolation and structural elucidation of a key aluminoaromatic intermediate and evidence for dismutation phenomena in TMP-alumination chemistry.

Lithium TMP-aluminate "(i)Bu(3)Al(TMP)Li" undergoes dismutation in THF solution to precipitate the tetraalkylaluminate [{Li.(THF)(4)}(+){Al((i)Bu)(4)}(-)], but reacts kinetically as a TMP base towards N,N-diisopropylbenzamide to afford the crystalline ortho-aluminated species [(THF)(3).Li{O([=C)N((i)Pr)(2)(C(6)H(4))}Al((i)Bu)(3)] and TMPH.

Structural variations in bimetallic sodium-magnesium and sodium-zinc ketimides, and a sodium-zinc alkide-alkoxide-amide: connections to ring-stacking, ring-laddering, and inverse crown concepts.

The first sodium-magnesium and sodium-zinc ketimido complexes display contrasting inverse crown ring and pseudo-cubane structures respectively, while a sodium-zinc heterotrianionic alkide-alkoxide-amide adopts a third type of structure with a stepped ladder motif.

Dizincation and dimagnesiation of benzene using alkali-metal-mediated metallation.

Benzene can be easily 1,4-dideprotonated stoichiometrically on reaction with two equivalents of a synergic mixture of tBu2Zn, NaTMP and TMEDA to give a unique 1,4-dizincated benzene product which has been characterised by X-ray crystallography and NMR spectroscopy as well as modelled theoretically by DFT computational studies; a related synergic dimagnesiation of benzene is also reported.

New reactivity and structural insights of alkali-metal-mediated alumination in directed ortho-alumination of a tertiary aromatic amide.

The first reported sodium alkyl(TMP)aluminate reagent to be synthesised and crystallographically characterised, [TMEDA.Na(mu-TMP)(mu-(I)Bu)Al((I)Bu)2], reacts as an amido base towards phenylacetylene to form crystalline [(TMEDA)2.Na(mu-CCPh)(mu-(I)Bu)Al((I)Bu)2]; whereas the congeneric TMEDA-stabilised lithium (TMP)aluminate exhibits dual alkyl/amido basicity in its reaction with N,N-diisopropylbenzamide to form a novel heterobimetallic-heterotrianionic crystalline complex [{PhC(=O)N(iPr)2}.Li{2-[1-C(=O)N(iPr)2]C6H4}{Me2NCH2CH2N(Me)CH2}Al(iBu)2], which, in addition to having an ortho-deprotonated benzamide ligand, also contains a methyl-deprotonated TMEDA ligand and a neutral benzamide molecule ligated to lithium.

Building an extended inverse crown motif via alkali-metal-mediated alpha-magnesiation of furan.

deprotonated selectively at the -position by the mixed-metal alkyl-amido base [(TMEDA) x Na(Bun)(TMP)Mg(TMP)] to generate a transient intermediate which undergoes disproportionation to the disodium dimagnesium hexafuryl tri(thf) complex [{{(thf)3 x Na2}{(TMEDA) x Mg2}(2-C4H3O)6}infinity], a new type of inverse crown structure with triply-stabilized (through Mg-C , Na-O and Na...C-C interactions) furyl guest anions, and the tris(amide) [(TMEDA)x.NaMg(TMP)3].