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Abstract: Alkyltrifluoroborates were used for Rh(III)-catalyzed ortho-alkylation of 2,4-disubstituted quinazoline via C-H bond activation. The reaction proceeded well with a broad substrate scope, providing a direct way to access high [...]

Abstract: The molecular bis-(tris(carbene)borate) manganese(IV) complex [[{PhB[(MeIm).sub.3]}.sub.2]Mn][(OTf).sub.2] shows [.sup.2][E.sub.g] → [.sup.4][A.sub.2g] luminescence at 828 nm in the solid state at 85 K; this wavelength is longer by approximately 100 nm [...]

Aqueous phase reaction of trialkyloxonium tetrafluoroborates, [R.sub.3][O.sup.+]B[F.sub.4.sup.-] (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide and several oxoanions or their corresponding oxoacids. Gaseous products were separated and identified by gas chromatography mass spectrometry (GC-MS). Alkylated derivatives RI, RBr, RCl were obtained for iodide, bromide, and chloride, respectively, while for fluoride its conversion efficiency to RF is very poor. RCN and [R.sub.2]S were obtained for cyanide and sulphide, while thiocyanate gives RSCN as a main reaction product with a minor amount of alkylisothiocyanate, RNCS (

Borate is an antibacterial preservative widely used in clinical and large-scale epidemiological studies involving urine sample analysis. Since it readily forms covalent adducts and reversible complexes with hydroxyl and carboxylate groups, the effects of borate preservation in [sup.1]H NMR-spectroscopy-based metabolic profiling of human urine samples have been assessed. Effects of various concentrations of borate (range 0-30 mM) on [sup.1]H NMR spectra of urine were observed at sequential time points over a 12 month period. Consistent with known borate chemistry, the principal alterations in the [sup.1]H resonance metabolite patterns were observed for compounds such as mannitol, citrate, and [alpha]-hydroxyisobutyrate and confirmed by ESI-MS analysis. These included line-broadening, [T.sub.1] and [T.sub.2] relaxation, and chemical shift changes consistent with complex formation and chemical exchange processes. To further investigate complexation behavior in the urinary metabolite profiles, a new tool for visualization of multi-component relaxation variations in which the spectra were color-coded according to the [T.sub.1] and [T.sub.2] proton relaxation times respectively ([T.sub.1] or [T.sub.2] ordered projection spectroscopy, TOPSY) was also developed and applied. Addition of borate caused a general decrease in [sup.1]H [T.sub.1] values, consistent with nonspecific effects such as solution viscosity changes. Minor changes in proton [T.sub.2] relaxation rates were observed for the most strongly complexing metabolites. From a molecular phenotyping and epidemiologic viewpoint, typical interpersonal biological variation was shown to be vastly greater than any variation introduced by the borate complexation, which had a negligible effect on the metabolic mapping and classification of samples. While caution is indicated in the assignment of biomarker signals where metabolites have diol groupings or where there are adjacent hydroxyl and carboxylate functions, it is concluded that borate preservation is 'fit-for-purpose' for [sup.1]H NMR-based epidemiological studies, since the essential biochemical classification features of the samples are robustly maintained.

The crystal structure of [Al.sub.4][B.sub.2][O.sub.9], synthesized from Al[(NO).sub.3] x 9[H.sub.2]O and B[(OH).sub.3] via a sol-gel process, is studied and characterized by Rietveld refinements and grid search analyses combined with [sup.11]B and [sup.27]Al MAS NMR spectroscopy. The aluminum borate with a unit-cell composition of [Al.sub.32][B.sub.16][O.sub.72] is closely related to the boralsilite ([Al.sub.32][B.sub.12][Si.sub.4][O.sub.74]) structure with Si replaced by B and to mullite ([Al.sub.4+2x][Si.sub.2-2x][O.sub.10-x]). It crystallizes in the monoclinic space group C2/m, a = 14.8056(7) [Angstrom], b = 5.5413(2) [Angstrom], c = 15.0531(6) [Angstrom], [beta] = 90.913(2)[degrees], Z = 8 for [Al.sub.4][B.sub.2][O.sub.9]. The main structural units are isolated chains of edge-sharing Al[O.sub.6]-octahedra running parallel to b that is a characteristic feature of the mullite-type crystal structures. The octahedral chains are crosslinked by Al[O.sub.4], Al[O.sub.5], B[O.sub.3], and B[O.sub.4] groups with two B atoms and one O atom (O5') disordered on interstitial positions. [sup.27]Al and [sup.11]B NMR studies confirm the presence of sixfold (octahedral), fivefold, and fourfold (tetrahedral) coordinated Al (sixfold:[fourfold + fivefold] = ~50%:50%) and of threefold and fourfold coordinated B (~80%:20%). Keywords: Aluminum borate, boron aluminate, [Al.sub.4][B.sub.2][O.sub.9], boralsilite, crystal structure, Rietveld refinement, MAS NMR spectroscopy

The tracer diffusion of [super 22]Na in sodium borate glass and of Rb in a rubidium borate glass is studied as functions of hydrostatic pressures to explore the atomistic mechanisms of ionic motion in glasses. The decrease in Haven ratio, which is found to be larger for Rb ions than Na ions, is attributed to the affect of pressure on the topology of the conduction pathways for migrating vacant cation sites.

A study reports about the geometric structures, spectroscopic properties, and electronic structures of copper(II)-nitrio complexes as a function of second coordination sphere effects employing a set of closely related coligands. The results demonstrate a significant difference in the electronic structures of N- vs O-coordinated nitrite as reflected by the vibrational properties and that the coordination mode of the N[O.sub.2-] ligand itself critically depends on the nature of the coligands.

The development of an in vitro assay system for the rapid detection and quantification of the furanosyl borate diester (BAI-2) subclass of autoinducer 2 (AI-2), quorum-sensing (QS) molecules is described. The sensor is based on ligand binding-induced changes in fluorescence resonance energy transfer (FRET) and LuxP with the evidence suggesting that FRET changes are BAI-2 dependent.

X-ray crystallography is used to study the synthesis, structure and the properties of manganese(III)-poly(pyrazolyl)borate complexes, which are low-spin in solution and the solid state. The structural changes due to the presence of 3-methyl substituents are equal or more important than the simple metal-ligand bond lengthening in accommodating the steric demands of the 3-methyl groups in bis(Tp*) complexes.

A study was conducted to investigate the infrared and vibrational circular dichroism (VCD) spectra of six chiral oxorhenium(V) complexes bearing a hydrotris(1-pyrazolyl)borate (Tp) ligand. These complexes are promising candidates for observation of parity violation (symmetry breaking due to the weak nuclear force). The VCD spectroscopy could be applied to determining the chirality of inorganic complexes.

A new synthetic pathway to the synthesis of bulky tris(carbene)phenylborate ligands and their cobalt(II) complexes is developed. It is found that the bulky ligands stabilize coordinately unsaturated cobalt(II) centers but unexpectedly, the cobalt complexes are extremely acid-sensitive with the 'tail' of the scorpionate ligand undergoing reversible protonation.

Sum frequency generation spectroscopy is used to study the influence of water on the surface of the water-miscible ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]. The results suggest that water has no drastic effect on the surface orientation of [BMIM][BF4] cation for concentrations from 0.0002[X.sub.IL] to 1[X.sub.IL].

Osmium(II) trispyrazolylborate complexes are synthesized by replacing the [[C.sub.5][Me.sub.5]] ligand in [[C.sub.5][Me.sub.5]] osmium complexes by ancillary groups like Trispyrazolylborate (Tp). NMR and IR data for these complexes are reported and it is investigated whether the strongly directional frontier orbitals of the TpM fragment would change the chemistry relative to their [[C.sub.5][Me.sub.5]] Os analogues.

The double bond of 2,3-dimethyl-2-butene (DMB) was very receptive to addition and even at -15degrees C instead of being inhibited to addition of Th+ by its four attached methyl groups. The reaction of Th+ with DMB was followed with cyclic voltammetry and was found to exhibit redox catalysis in which Th was generated.

A systematic investigation of the dielectric spectra of aqueous solutions of NaBPh4 and Ph4PCl as representative salts containing these ions is described, with a view of comparing their hydration behavior. BPh(sub 4)(super -) and Ph4P(super +) have shown almost identical hydration characteristics, providing indirect support for the use of the tetraphenylphosphonium tetraphenylborate reference electrolyte assumption in deriving single-ion thermodynamic properties.

Acid-assisted reductive elimination of hydrogen from Tp'ptH3 and of methane and hydrogen from Tp'PtMeH2 (Tp'=hydriodotris(3,5-dimethylpyrazolyl)borate) is examined. Loss of H2 from solutions containing platinum(IV) complexes of the type Tp'Pt(R)(H)2 (R=Me, H) is observed upon protonation and addition of a ligand such as CO.

The reactions of the Lewis acid-base adduct (THF)B(C6F5)3 with sterically demanding phosphines and phosphides are probed. A demonstration that such reactions affect the facile and quantitative ring opening of tetrahydrofuran (THF ), affording synthetic routes to zwitterionic phosphonium borates or the lithium salt of a phosphine borate is presented.

The synthesis and characterization of carbonyloxo- and carbonylsulfidotungsten(IV) complexes containing hydrotris(3,5-dimethylpyrazol-1-yl)-borate is reported. The complex exhibits a symmetrical, binuclear structure with a linear W-O-W unit.

Data highlighting the poor performance of B3LYP for B-N dative bonds is presented. The differences of 7, 10, 3, and 11 kcal/mol between MP2 and B3LYP dissociation energies for then systems, 2-AMB, 2-APB, (HO)H(sub 2)B-NH(sub 3) and CH(sub 3)O(CH(sub 3))(sub 2)B-NH(sub 2)Ch(sub 3), respectively are observed.

The synthesis and crystal structure analysis of the ditopic p-phenylene-bridge bis(pyrazol-1-yl)borate ligand [[p-C(sub 6)H(sub 4)-(Bpz(sub 2)tBu)(sub 2)]Li(sub 2)] is described. Reaction of LLi(sub 2) with [Ti(NMe(sub 2))(sub 2)Cl(sub 2)]and water the mu-oxo-bridged dititanium species [L[Ti(NMe(sub 2))Cl](sub 2)(mu-O)] is obtained in excellent yield.

The NH/pi interaction in the spin crossover (SC ) phenomenon, synthesis and characterization of spin-cross-over complex are investigated. It is found that the NH/pi interactions play an important role in SC phenomenon

A new generation of triazine-based coupling reagents (TBCRs), designed according to the concept of 'superactive esters', was obtained by treatment of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium (DMTMM) chloride with lithium or silver tetrafluoroborate. It is proved that the concept of 'superactive esters' is a tool useful for designing new coupling reagents and are highly versatile in ester and peptide synthesis in solution as well as in the solid phase.

The activation energies for the racemization of C3-symmetric complexes of four- and six coordinate metals with hydrotris(methimazolyl)borate lignad are explored by variable-temperature NMR and ab initio calculations. All of the four-coordinate complexes studied are found to follow a dissociative mechanism of racemization with activation energy dependent upon solvent donor ability.

Direct iodination of 2,2'-bis(diphenylphosphino)-1-1'-binaphthyl (BINAP) dioxide with iodine monochloride and N-iodosucinimide in the presence of trifluoroacetic acid is discussed. Derivatization at the 5,5'-positions to BINAP does not influence enantioselectivities or yields in rhodium-catalyzed asymmetric 1,4-additions.

An efficient kinetic resolution of racemic Betti base with L-(+)-tartaric acid in acetone is developed based on a novel enantioselective N,O-dekatalization. The enantiopure R- and S-enantiomers of Betti base are obtained as the corresponding N,O-ketal compound and salt with L-(+)-tartaric acid, respectively, in excellent yields with a practically foolproof operation.

M-H-B bridges and M...alpha-H-C agostic interactions with Eu(II), Yb(II), and K cations occur in a series of 9-BBN hydroborate, [H(sub2)BC(sub8)H(sub14)](super -), complexes. The preparation, the structural and the spectroscopic characterization of Eu(II) and Yb(II) 9-BBN hydroborates is reported.

Several cyclic 2-(methylthio)-5-amidofurans containing tethered unsaturation are prepared through the reaction of dimethyl(methylthio)sulfonium tetrafluoroborate (DMSTF) with beta-alkokxy-gamma-duthiane lactams. Thermolysis of these furans resulted in an intramolecular Diels-Alder reaction.

Simple beta-lactams and their hydrolysis products, the beta-amino acids react with Tp*Zn-OH under deprotonation. Beta-lactams bearing nitrophenyl or acyl substitutes at the nitrogen atoms are opened hydrolytically by Tp*Zn-OH and the resulting N-substituted beta-amino acids are attached to zinc by their carboxylate functions.

The sonogashira reaction proceeds at ambient temperature in acetone or room temperature ionic liquid, 1, 3-di-n butylimidazolium tetrafluoroborate ([bbim]BF4), as solvent under ultrasound irradiation to give enhanced reaction rates, excellent chemoselectivity, and high yields. The formation of stable, crystalline, and polydispersed Pd(0) nanoparticles as catalyst for the reaction is shown in the analysis.

Preparation of air-stable PBO tetrafluoroborate salts as precursors to PBO catalysts is described. The stability of the salts allows accurate quantification of the precatalyst in air.

Alkoxide exchange is observed using methanol, ethanol, and trifluoroethanol. It is stated that with the NH acids cyanamide trifluroracetamide, and pyrazoles, the corresponding anions are attached to zinc, and likewise beta and gamma-lactams, a thiazolidinedione, and the cyclic sulfimide saccharin are deprotonated.

The methoxides Tp (super Ph, Me) Zn-OMe and Tp (super Cum, Me) Zn-OMe are tested for their reactivity substrates that are hydrolytically cleaved with Tp*Zn-OH complexes. The findings indicated that, while the leaving group properties of the methoxide unit are essential, it is the strength of the resulting zinc-substrate bonds that decides upon the occurrence or nonoccurrences of the cleavage reactions.

Alkylations with methyl iodide have revealed the high nucleophilicity of Tp (super Ph, Me) Zn-OMe by conversion to dimethyl ether and Tp (super Ph, Me) Zn-1. This conversion occurs rapidly not only with pure Tp (super Ph, Me) Zn-OMe but also with Tp (super Ph, Me) Zn-OH and with Tp (super Ph, Me) Zn-OCOOMe.

The voltammogram of aryldiazonium tetrafluoroborates in acetonitrile, at low concentration, shows a first one-electron wave followed at a more negative potential by a small second wave. It is shown that the last wave corresponds to the reduction of the radical formed at the level of the first wave.

The chiral borate counteranion bis[(R)-1,1'-bi-2-naphtholato]borate ([1.sup.-]) has been found to be a competent chiral [sup.1]H NMR shift reagent for cationic copper(I) complexes. This has been demonstrated by the addition of the Cu[(NCMe).sup.+.sub.4] salt of 1- to two classes of common chiral ligands in asymmetric catalysis: 2, 2'-bis(di-p-tolylphosphino)1,1'-binaphthyl (tol-BINAP) (2) and 2, 2'-isopropylidenebis(4-phenyl-2-oxazoline) (3). In the case of ligand 2, the addition of 1 equiv. of either (R,R)-2 or (S,S)-2 to Cu[(NCMe).sup.+.sub.4][1.sup.-] results in well-resolved [sup.1]H NMR resonances for the two enantiomers. Examination of standard solutions of non-enantiopure 2 shows that the copper complex can be an effective NMR shift reagent of a wide range of enantiomeric compositions. Cu[(NCMe).sup.+.sup.4]1- also generates distinct [sup.1]H NMR resonances for the two separate enantiomers of 2, 2'-isopropylidenebis(4-phenyl-2-oxazoline) (3). However, attempts to employ this copper salt as a chiral NMR shift reagent for rac-3 led to the discovery of a new and unexpected equilibrium: [(R,R)-3] [Cu.sup.+] + [(S,S)-3][Cu.sup.+] [??] [(R,R)-3][(S,S)-3][Cu.sup.+] + [Cu.sup.+]. Key words: chiral counteranion, copper, chiral NMR shift reagent, ion pairing.

A three-dimensional redox system: tetra is- {4-[N, N-di (4-methoxyphenyl) amino] phenyl} phosphonium tetrafluoroborate 1(super +) BF (sub 4)(super -) which comprises of four triarylamine redox centers arranged in a pseudo-tetradral geometry is used to investigate different electron-transfer pathways. Findings indicate that just as two consecutive one-electron transfer steps are allowed, both the photoexcited as well as the thermal ET in 1(sup 3+) are forbidden as a concerted two-electron transfer.

The synthesis, the solid-structure and solution behavior of a series of samarium compounds of the type Sm(Tp(super Me2))(sub 2)L with L being a bidentate ligand is reported. The results show the subtle differences in the barriers to the rotations of the various ligands that point toward the potential for steric control in these systems.

The preparation and characterization of the manganese(I) tricarbonyl complex PhB[(Melm).sub.3]Mn[(CO).sub.3] is presented. Both IR and CV measurements of these complexes attest to the remarkable donor properties of tris(carbene)borates and their ability to stabilize higher oxidation states.

The synthesis and single-crystal X-ray diffraction study of the [1,8-[C.sub.10][H.sub.6][(NM[e.sub.2]).sub.2]H][[B.sub.5][O.sub.6][(OMe).sub.4]] salt is presented. The slow hydrolysis of B[[OMe).sub.3] in a C[H.sub.2]C[l.sub.2] solution in the presence of 1,8-[C.sub.10][H.sub.6][(NM[e.sub.2]).sub.2] (5:1 ratio) resulted in the formation of the novel isolated pentaborate ester anion [[[B.sub.5][O.sub.6][(OMe).sub.4]].sup.-]].

The perrhenate exchange chemistry of Pb[B(lm)4]-(NO3)(nH2O), resulting in complete replacement of the nitrates with perrhenate to form Pb[B(lm)4](ReO4) with retention of crystallinity in the network solid is presented. It is found that such a synthetic metal organic framework solid represents a new candidate for pertechnetate-sequestering materials.

X-ray crystal characterization of mono- and ditopic lithium ferrocenylhydridoborates Li[FcB[H.sub.3]] and [Li.sub.2][[H.sub.3]B-fc-B[H.sub.3]] synthesized from FcB[(OMe).sub.2]/[(MeO).sub.2]B-fc-B[(OMe).sub.2] and Li[Al[H.sub.4]] (Fc = ferrocenyl; fc = 1,1'-ferrocenylene) is reported. Dimeric or tetrameric aggregates observed in the solid state is dependent on the amount of [Li.sup.+]-coordinated solvent molecules.