Versatile behavior of 2-guanidinobenzimidazole nitrogen atoms toward protonation,coordination and methylation

The structure, dynamic behavior, protonation, methylation, and coordination sites of 2-guanidinobenzimidazole 1a were investigated. Structures of compounds [2-guanidinium-1,3,10-trihydrobenzimidazole]sulfate 1b , [2-guanidinium-1,3-dihydro-benzimidazole]sulfate 1c–1d , [2-guanidinium-1,3-dihydro-benzimidazole]tetrafluoroborate 1e , [2-guanidinium-1,3-dihydro-benzimidazole]chloride 1f , [2-guanidinium-1,3-dihydro-benzimidazole] perchlorate 1g , 2-guanidino-1-methyl-benzimidazole 2a , [2-guanidinium-1,3-dimethyl-benzimidazole]iodide 2b , [2-guanidinium-1-methyl-3-hydro-benzimidazole]chloride 2c , [2-guanidinium-1,10-dihydro-benzimidazole]acetate 3 , 2-guanidino-1-hydro-3-borane-benzimidazole 4a , 2-guanidino-1-methyl-3-borane-benzimidazole 4b , (2-guanidino-benzimidazole)dimethyltin 5 , [bis(2-guanidino-10-hydro-benzimidazole)nickel(II)] 6 , and [bis(2-guanidino-1,10-dihydro-benzimidazole)zinc(II)]nitrate 7 were determined based on ¹H, ¹³C, and ¹⁵N NMR spectroscopy. The X-ray diffraction structures of 2a, 2b, 3, 6 , and 7 were obtained. The results show that 1a has an open structure without an intramolecular hydrogen bond in DMSO or DMF. The imidazolic N-3 is the preferred basic site in solution for protonation, methylation, and coordination and not N-10 as was suggested from semiempirical calculations. Under strong acidic conditions, diprotonation occurs at N-3 and N-10. In the solid state, 3 and 6 were protonated preferently at N10 rather than at N-1. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 397–410, 1997     

Hydroacridines: Part 23. 1H and 13C NMR spectra of sym‐octahydroacridine,its 9‐(3‐pyridyl) and 9‐(4‐pyridyl) derivatives and the corresponding N(10)‐oxides. An experimental approach to the diamagnetic anisotropy of the pyridine nucleus

The complete ¹H NMR chemical shift assignments of 1,2,3,4,5,6,7,8‐octahydroacridine ( 1 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(3‐pyridyl)acridine ( 2 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(4‐pyridyl)acridine ( 3 ) and the corresponding N(10)‐oxides 1a , 2a and 3a , respectively, were achieved on the basis of 400 MHz ¹H NMR spectra and proton–proton decoupling, HMQC and NOEDIFF experiments. The spectral data for the above compounds provided the first experimental evidence of the difference in the anisotropy effect of the two non‐symmetrical moieties of the pyridine nucleus, and allowed us to ascertain that the shielding effect of the moiety defined by the C(2′)—N—C(6′) atoms is weaker than that of the C(3′)—C(4′)—C(5′) moiety. The ¹³C NMR spectra of 1 – 3 and 1a – 3a and the effect of N(10)‐oxidation on the ¹³C NMR chemical shifts are also discussed. The N‐oxidation of 2 and 3 with m‐chloroperbenzoic acid occurred regiospecifically, affording the N(10)‐oxides 2a and 3a free of N(1′)‐oxide isomers. Copyright © 2002 John Wiley & Sons, Ltd.     

Structure of N-(1-silatranylmethyl) and N-(trimethoxysilyl-methyl) derivatives of nitrogen-containing heterocycles according to data of NMR, IR, and UV spectroscopy

The ¹H, ¹³C, ¹⁵N, and ²⁹Si NMR, IR, and UV spectra of N-(1-silatranylmethyl) and N-(trimethoxysilylmethyl) derivatives of nitrogen heterocycles have been studied. The dependence and interrelation of the chemical shifts of ²⁹Si and ¹⁵N nuclei of the silatranyl group in the spectra of N-(1-silatranylmethyl)-substituted nitrogen heterocycles are determined by the nature of the heterocyclic system. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1857–1865, December, 2006.     

The B–N Bond in Some Aminoboranes and an Iminoborane,Studied by 11B and 15N NMR Spectroscopy and DFT Methods

¹⁵N NMR spectra of several aminoboranes (Me₂B–NMe₂, Cl₂B–NMe₂, Br₂B–NMe₂, OCH₂CH₂OB–NMe₂), three N‐pyrrolylboranes, and an iminoborane (tBu–B≡N–tBu) was measured. The spin‐spin coupling constants ¹J(¹⁵N, ¹¹B) were resolved at elevated temperatures. In the case of the iminoborane at 105 °C, the coupling constant ¹J(¹⁴N,¹¹B) = 57 Hz could also be determined from the ¹¹B NMR spectrum [from ¹⁵N NMR ¹J(¹⁵N,¹¹B) = 81 Hz]. Generally, there is no correlation between the magnitude of ¹J(¹⁵N,¹¹B) and the bond length d_BN. The values ¹J(¹⁵N,¹¹B) indicate that changes in σ bonding affect their magnitude, and the nature of the lone pair of electrons at nitrogen is of great importance. The calculated NMR parameters of an adduct of the iminoborane with an N‐heterocyclic carbene, show that the bonding situation around the BN double bond in the adduct is comparable with imines.     

On the reaction of aminobis(diorganylamino)phosphanes with halogenophosphanes—P-hydrogeno(iminophosphoranyl)-halogenophosphanes and P-hydrogeno(iminophosphoranyl)-σ2, λ3-iminophosphanes

Reactions of triaminophosphane (R₂N)₂P–NH₂, (R = ¹Pr) 1a, with aminodihalogenophosphanes ¹Pr₂N–PX₂, 2a–c [X = CL (a), Br (b), I(c)], in the presence of a base yielded the P-hydrogeno-iminophosphoranyl-halogenophosphanes (R₂N)₂PH = N–PX–N(¹Pr)₂ 4a–c [X = Cl (a), Br (b), I(c)]. Analogous reactions between 1a and 1b (b: R = c-hexyl) and chloroiminophosphane (Cl–P = N–Mes^*, (Mes^* = 2,4,6-^tBu₃C₆H₂) 6 , gave the P-hydrogeno(iminophosphoranyl)-σ²,λ³-iminophosphanes, (R₂N)₂PH = N–P = N–Mes^* 8a and 8b. In solution 8a, 8b eliminated amine, yielding σ², λ³-iminophosphanyl-substituted 1,3,2,4-diazadiphosphetidines [(R₂N)PN(P = N–Mes^*)]₂, 10a, 10b , and 11 ( 10a and 10b : cis; 11: trans). The X-ray structure analyses of compounds 4a, 4b, 8a, and 11 are discussed. © 1996 John Wiley & Sons, Inc.     

NMR studies in the heterocyclic series XXIV—1H, 13C and 15N study of 15N labelled indazoles

The ¹⁵N chemical shifts and ¹H? ¹⁵N and ¹³C? ¹⁵N coupling constants of nine monolabelled indazoles were measured and assigned. The experimental values are discussed in terms of the indazolic and iso-indazolic structures, and compared with literature data for other related heterocycles. All the results are consistent with an N-1(H) tautomeric structure for indazole in DMSO-d₆.     

Photochemistry of 6,6-Dimethyl- and 2,2,6,6-Tetramethyl-2H,6H-pyran-3-one

The title compounds 1a and 1b have been synthesized in two steps from the saturated pyran-3-ones 2a and 2b , respectively. Upon irradiation (254 nm or 350 nm) in dilute solutions (10^?3?10^?2M ), compounds 1 undergo a formal [4 + 2] cycloreversion from the excited triplet state to give (2-methylprop-1-enyl)ketene ( 11 ) and either formaldehyde or acetone, ketene 11 being trapped by H₂O or MeOH to afford 4-methylpent-3-enoic acid ( 5 ) or its methyl ester 4 in 75–85% isolated yield. In this (monomolecular) photoreaction, heterocycles 1 differ from their alicyclic counterparts, i.e., 4,4-dimethylcyclohex-2-enone ( 10a ) and 4,4,6,6-tetramethylcyclohex-2-enone ( 10b ), as no rearrangement to a 4-oxabicyclo[3.1.0]hexan-2-one occurs. On the other hand, the photochemical behavior of pyranone 1a in bimolecular reactions (cyclodimerization, [2 + 2] cycloaddition to 2,3-dimethylbut-2-ene) resembles that of enone 10a .     

Darstellung, 11B-NMR-, Schwingungsspektren und Kristallstruktur von (PPh4)[1-(NO)B10H9]

Synthesis, ¹¹B NMR, Vibrational Spectra, and Crystal Structure of (PPh₄)[1-(NO)B₁₀H₉] By reaction of (n-Bu₄N)₂[B₁₀H₁₀] in aqueous acetonitrile with NO₂ a reaction mixture is formed from which [1-(NO)B₁₀H₉]^– has been isolated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose. The X-ray structure determination of (PPh₄)[1-(NO)B₁₀H₉] (triclinic, space group P1, a = 7.6553(11), b = 13.179(2), c = 14.122(3) Å, α = 69.853(13), β = 82.445(14), γ = 87.230(13)°, Z = 2) reveals the coordination of the NO group via N in an apical position of the B₁₀ cluster with B1–N = 1.457(5) and N–O = 1.101(4) Å. The ¹¹B NMR spectrum exhibits the characteristic feature (1 : 1 : 4 : 4) of a in 1 position substituted B₁₀ cluster with a strong downfield shift of the ipso-B atom at +6.5 ppm. The IR and Raman spectra show a strong NO stretching vibration at 2219 cm^–1.     

Regioselectivity and regiospecificity of benzoxazinone (2-isopropyl-4H-3,1-benzoxazinone) derivatives toward nitrogen nucleophiles and evaluation of antimicrobial activity

A novel group of 6-iodoquinazolin-4(3H)-one derivatives was prepared. The reaction of the benzoxazinone 3 with various nitrogen nucleophiles such as formamide and hydrazine hydrate and also the reaction of the isopropylquinazolinone 4 with hydrazonyl chloride have been shown to proceed with a high degree of regioselectivity at C(2). Spiro heterocycles have been found to play fundamental roles in biological processes and have exhibited diversified biological activity and pharmacological and therapeutical properties; thus reaction of acetohydrazides 10a–c afforded the spiro compounds 11a–c. The acetohydrazide derivative 7 reacted with carbon electrophiles such as acetylacetone, ethyl acetoacetate, acid chlorides, and benzaldehyde to give some interesting heterocyclic compounds 12–16, respectively. The structures of all the synthesized compounds were inferred by infrared, ¹H NMR, and mass spectra as well as elemental analyses. The antimicrobial activities of some of the synthesized products were preliminarily evaluated.     

Bipyridinophane‐containing conjugated polymers modulated with an intramolecular aromatic C?H/π interaction

Bipyridinophane–fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8‐dibromo‐2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane and suitable fluorene precursors. Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P7 ) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐1,4‐(2,5‐dimethylbenzene)] ( P11 ), which bears the same polymer backbone as P7 . These spectral shifts originate from intramolecular aromatic C? H/π interactions, which are evidenced by ultraviolet–visible and ¹H NMR spectra as well as X‐ray single‐crystal structural analysis. However, the effect of the intramolecular aromatic C? H/π interactions on the spectral shift in poly[9,9‐dihexylfluorene‐2,7‐yleneethynylene‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P10 ) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mn²⁺, and Ag⁺ ions. In contrast, only Cu²⁺, Co²⁺, and Ni²⁺ ions can partially quench the fluorescence of P10 , but much less efficiently than the fluorescence of P7 . The static Stern–Volmer quenching constants of Cu²⁺, Co²⁺, and Ni²⁺ ions toward P7 are of the order of 10⁶ M^?1, being 1300, 2500, and 37,300 times larger than those of P10 , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4154–4164, 2006     

A Dimeric Gallium Hydrazide as an Active Lewis Pair – Complexation and Activation of Me2GaH and Various Heterocumulenes

Treatment of the dimeric gallium hydrazide [Me₂Ga‐N(2‐Ad)‐NC₅H₁₀]₂ ( 5 ) with Me₂GaH resulted in the formation of an adduct 6 by Ga–N bond cleavage and coordination of the metal hydride via a Ga–N and a 3c–2e Ga–H–Ga bond. This reaction reflects the typical behavior of frustrated Lewis pairs. Reactions with heterocumulenes R–N=C=X (R = Ph, CMe₃, Dipp, X = O; R = Ph, X = S) or X=C=X (X = O, S) resulted in the formation of the cyclic Ga–N insertion products Me₂Ga–N(R)C(O)N(2‐Ad)‐NC₅H₁₀ ( 7a – c ), Me₂GaS₂C‐N(2‐Ad)‐NC₅H₁₀ ( 8 ) or Me₂GaX₂C‐N(2‐Ad)‐NC₅H₁₀ [X = O ( 9 ); S ( 10 )] in moderate to good yields. Three different structural motifs were observed in the solid state: Five‐membered GaNCN₂ heterocycles with exocyclic C=O bonds for compounds 7a – c , four‐membered GaSCN or GaSCS heterocycles for compounds 8 and 9 (chelating coordination of the Ga atoms by SCN and CS₂ ligands) and an eight‐membered (GaOCO)₂ heterocycle for the dimeric CO₂ insertion product 10 . Treatment of 5 with PhCN or Ph₂CO resulted in a completely different reaction and afforded a dimeric Ga imide 11a or an alcoholate 11b . These reactions may start by retro‐hydrogallation with the formation of H₁₀C₅N–N=C(C₉H₁₄) and Me₂GaH and proceed by addition of the metal hydride to the polar multiple bonds of the nitrile or ketone.     

Boron coordination compounds derived from 2-phenyl-benzimidazole and 2-phenyl-benzotriazole bidentate ligands

The syntheses and structural analyses of a series of boron heterocycles derived from 2-(1H-benzimidazol-2-yl)-phenylamine (1), 2-(1H-benzimidazol-2-yl)-phenol (2), 2-(1H-benzimidazol-2-yl)-benzenedisulfide (3), 2-[3-(1,1,1,3,-tetramethyl-butyl)-phenyl]-2H-benzotriazole (4), 2-[3,5-bis-(1-methyl-1-phenylethyl)-phenyl]-2H-benzotriazole (5) and (C₆H₅)₂BOH or BF₃·OEt₂ are reported. The new boron compounds: diphenyl-[2-(1H-benzimidazol-2-yl-κN)-phenylamide-κN]-boron (6), diphenyl-[2-(1H-benzimidazol-2-yl-κN)-phenolate-κO]-boron (7), diphenyl-[2-(1H-benzimidazol-2-yl-κN)-benzenethiolate-κS]-boron (8), diphenyl-[2-(2H-benzotriazol-2-yl-κN)-4-(1,1,3,3-tetramethyl-butyl)-phenolate-κO]-boron (9), diphenyl-[2-(2H-benzotriazol-2-yl-κN)-4,6-(1-methyl-1-phenylethyl)-phenolate-κO]-boron (10), difluoro-[2-(1H-benzimidazol-2-yl-κN)-phenolate-κO]-boron (11), difluoro-[2-(2H-benzotriazol-2-yl-κN)-4-(1,1,3,3-tetramethylbutyl)-phenolate-κO]-boron (12) and difluoro-[2-(2H-benzotriazol-2-yl-κN)-4,6-(1-methyl-1-phenylethyl)-phenolate-κO]-boron (13) have four fused rings, with boron included in a six-membered ring and bound to N, O or S atoms and strongly coordinated by a nitrogen atom from the imidazole or triazole rings. Their structures are zwitterionic, with a negative charge on the boron and a delocalized positive charge on the ligand. Compounds 6-12 were studied by NMR, IR, mass spectrometry, and 6-10 and 12 by X-ray diffraction analyses.     

Reactivity of TpMe2‐Supported Yttrium Alkyl Complexes toward Aromatic N‐Heterocycles: Ring‐Opening or CC Bond Formation Directed by CH Activation

Unusual chemical transformations such as three‐component combination and ring‐opening of N‐heterocycles or formation of a carbon–carbon double bond through multiple C–H activation were observed in the reactions of Tp^Me2‐supported yttrium alkyl complexes with aromatic N‐heterocycles. The scorpionate‐anchored yttrium dialkyl complex [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with 1‐methylimidazole in 1:2 molar ratio to give a rare hexanuclear 24‐membered rare‐earth metallomacrocyclic compound [Tp^Me2Y(μ‐N,C‐Im)(η²‐N,C‐Im)]₆ ( 1 ; Im=1‐methylimidazolyl) through two kinds of C–H activations at the C2‐ and C5‐positions of the imidazole ring. However, [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with two equivalents of 1‐methylbenzimidazole to afford a C–C coupling/ring‐opening/C–C coupling product [Tp^Me2Y{η³‐(N,N,N)‐N(CH₃)C₆H₄NHCH?C(Ph)CN(CH₃)C₆H₄NH}] ( 2 ). Further investigations indicated that [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with benzothiazole in 1:1 or 1:2 molar ratio to produce a C–C coupling/ring‐opening product {(Tp^Me2)Y[μ‐η²:η¹‐SC₆H₄N(CH?CHPh)](THF)}₂ ( 3 ). Moreover, the mixed Tp^Me2/Cp yttrium monoalkyl complex [(Tp^Me2)CpYCH₂Ph(THF)] reacted with two equivalents of 1‐methylimidazole in THF at room temperature to afford a trinuclear yttrium complex [Tp^Me2CpY(μ‐N,C‐Im)]₃ ( 5 ), whereas when the above reaction was carried out at 55 °C for two days, two structurally characterized metal complexes [Tp^Me2Y(Im‐Tp^Me2)] ( 7 ; Im‐Tp^Me2=1‐methyl‐imidazolyl‐Tp^Me2) and [Cp₃Y(HIm)] ( 8 ; HIm=1‐methylimidazole) were obtained in 26 and 17 % isolated yields, respectively, accompanied by some unidentified materials. The formation of 7 reveals an uncommon example of construction of a C?C bond through multiple C–H activations.     

Crystal Structure and Spectroscopic Characterization of Zinc(II) and Mercury(II) Complexes of N‐(Pyridin‐2‐ylmethylene)benzene‐1,4‐diamine

The behavior of N,N′‐bis(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L) towards zinc(II), cadmium(II), and mercury(II) chlorides was studied in methanol solutions. In the presence of metal ions, the organic molecule was decomposed to N‐(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L′), and complexes of general formula M(L′)Cl₂ were isolated from the mixture. The complexes were identified by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectra, and their structures were further confirmed by single‐crystal X‐ray diffraction analysis of Zn(L′)Cl₂ and Hg(L′)Cl₂. In the solid state of both complexes, the molecules are stabilized by N–H ··· Cl hydrogen bonds and aromatic π–π stacking interactions.     

Influences of steric bulkiness in hydrotris(pyrazolyl)borate ligands on ethylene polymerization reaction

Manganese(II) complex catalysts with hydrotris(pyrazolyl)borate ligands have been examined on their catalytic performance in ethylene polymerization and ethylene/1‐hexene copolymerization. The activities of [Mn(L6)(Cl)(NCMe)] ( 1 ) and [Mn(L10)(Cl)] ( 2 ) activated by Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] for ethylene polymerization go up to 326 and 11 kg mol (cat^?1) h^?1, respectively, (L6^? = hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate anion, L10^? = hydrotris(3‐adamantyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In particular, for ethylene/1‐hexene copolymerization, complex 1 gives high‐molecular‐weight poly(ethylene‐co‐1‐hexene)s with the highest M_w of 439,000 in manganese olefin polymerization catalyst systems. Moreover, the 1‐hexene incorporation by complex 1 seems more efficient than that by [Mn(L3)(Cl)] ( 4 ) (L3^? = hydrotris(3‐tertiary butyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In this work, we demonstrated that the coordination geometry and coordination number are also important factors for ethylene polymerization reaction as well as steric hindrances and ligand frameworks in our manganese(II) catalysts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5720–5727, 2009     

Synthesis and Characterization of N-(2,2-Diphenylacetyl)- N′-Substituted Thiourea Derivatives: The Crystal Structure of N-(2,2-Diphenylacetyl)-N′-(4-chloro phenyl)-thiourea

A series of new N-(2,2-diphenylacetyl)-N ′-substituted thiourea derivatives (1–9) have been prepared and characterized by elemental analyses, IR and ¹H NMR spectroscopy. N-(2,2-diphenylacetyl)-N ′-(4-chlorophenyl)-thiourea was also characterized by a single crystal X-ray diffraction study. The compound crystallizes in the monoclinic space group P2₁/c with Z = 4 and a = 9.6551(19) Å, b = 20.060(4) Å, c = 9.894(2) Å, β = 104.29(3)°. The molecular conformation of the compound is stabilized by an intramolecular (N1-H1···O1) hydrogen bond that forms a pseudo-six-membered ring.     

Umsetzung von 3-Amino-2H-azirinen mit Salicylohydrazid

Reaction of 3-Amino-2H-azirines with Salicylohydrazide 3-Amino-2H-azirines 1a–g react with salicylohydrazide ( 7 ) in MeCN at 80° to give 2H, 5H-1,2,4-triazines 10 , 1,3,4-oxadiazoles 12 and, in the case of 1d , 1,2,4-triazin-6-one 11a (Scheme 3). The precursor of these heterocycles, the amidrazone of type 9 , except for 9c and 9g , which could not be isolated, has been found as the main product after reaction of 1 and 7 in MeCN at room temperature. 3-(N-Methyl-N-phenylamino)-2-phenyl-2H-azirin ( 1g ) reacts with 7 to give mainly the aromatic triazines 15b₁ and 15b₂ . In this case, two unexpected by-products, 16 and salicylamide ( 17 ), occurred, probably by disproportionation of a 1:1 adduct from 1g and 7 (Scheme 8). Oxidation of 10f with DDQ leads to the triazine 15a . The structure of 10c, 11a, 12c, 13 (by-product in the reaction of 1b and 7 ), the N′-phenylureido derivative 14 of 9d (Scheme 4) as well as 15b₂ has been established by X-ray crystallography. The ratio of 10/12 as a function of substitution pattern in 1 and solvent has been investigated (Tables 1, 3, 4, and 7). A mechanism for the formation of 10 and 12 is proposed in Scheme 7.     

Diversity of supramolecular aggregation in copper(II) pentane-2,4-dionato compounds with methyl substituted 2-aminopyridines

Three copper(II) bis(pentane-2,4-dionato-κ ² O,O′) compounds with 2-amino-3-methylpyridine (2,3-ampy) (1), 2-amino-5-methylpyridine (2,5-ampy) (2), and 2-amino-4-methylpyridine (2,4-ampy) (3) were prepared by reaction of bis(pentane-2,4-dionato-κ ² O,O′)copper(II) with selected methyl substituted 2-aminopyridines. The coordination of Cu(II) in all three compounds is square pyramidal and intramolecular N–H?···?O hydrogen-bonding is present. X-ray crystallographic studies reveal different crystal aggregation influenced by a methyl substituent on pyridine. No intermolecular N–H?···?O hydrogen-bonding is present in 1. Intermolecular N–H?···?O hydrogen-bonding in 2 forms infinite chains and dimers are formed in 3. Extended 3-D aggregation was found in 2 via π–π and C–H?···?π (arene) interactions, while only chain formation was found in 1 and 3.     

High-Yield Syntheses of Sodium,Potassium, and Thallium Hydrotris[3,5-bis(trifluoromethyl)pyrazolyl]borates and the X-ray crystal structure of {hydrotris[3,5-bis(trifluoromethyl)pyrazolyl]borato} thallium(I)

An improved synthesis of 3,5-bis(trifluoromethyl)pyrazole ( 1 ) is described. This compound was used for the high-yield syntheses of the tris(pyrazoly1)borates Nd[HB(3,5-(CF₃),-pz)₃] ( 2a ) and the corresponding potassium salt, 2b , starting from 1 and NaBH₄ and KBH₄, respectively. A convenient route to the corresponding thallium(I) salt, 2c , using thallium(I) acetate and either 2a or 2b in CHCI₃, is also described. The sodium ( 3a ), potassium ( 3b ), and thallium ( 3c ) salts of bis(pyrazolyl)borate [H₂B(3,5-(CF₃)₂-pz)₂]^? were also prepared. The above pyrazolylborates were characterized by ¹H-, ¹³C-, ¹⁹F-, and ¹¹B-NMR spectroscopy. The X-ray crystal structure of the thallium derivative 2c was determined. The compound crystallizes in the monoclinic space group P2₁/m with a = 8.248(9) Å, b = 15.034(12) Å c = 9.243(8) Å, β = 100.10(7)°, Z = 2. The Tl-atom adopts a pyramidal geometry with respect to the three N-atoms. However, two TI–N distances (2.725(7) Å) are longer than the third (2.675(10) Å).