Volume 63, Issue 2

Treatment of the monomeric trialkylelement compounds Al(CMe 3 ) 3 , Ga(CMe 3 ) 3 , and In(CMe 3 ) 3 with different hydrazines H 2 N-N(H)R (R=Me, CMe 3 , C 6 H 5 ) yielded the corresponding adducts (Me 3 C) 3 E ← NH 2 -N(H)R, 1 to 9, in almost quantitative yields. All products were characterized by crystal structure determinations and shown to have the NH 2 group of the hydrazine ligands attached to the central Group 13 atom. These adducts are excellent starting compounds for the generation of hydrazides by thermolysis with release of butane

The N,O-chelates M(3,4-dehydro-D,L-prolinate) 2 (M = Ni, Cu) have been obtained from Ni(OH) 2 or Cu(OH) 2 and the amino acid. The complexes (R 3 P)(Cl)M(α-aminoacidate) (M= Pd, Pt) have been synthesized from the chloro bridged compounds (R 3 P)(Cl)M(μ-Cl) 2 M(PR 3 )Cl (M = Pd, Pt; R = Et, n-Bu, Ph) and the potassium salts of the α-amino acids D,L-serine, D,L-threonine, 3,4-dehydro-D,Lproline and 4-hydroxy-L-proline. According to the 31 P NMR and 13 C NMR spectra the complexes with serinate and threoninate are formed as mixtures of cis/trans N-M-P isomers, whereas for the palladium complexes with 3,4-dehydroprolinate and 4-hydroxyprolinate a single isomer is observed

A trinuclear cobalt(II) complex, [Co 3 (PhCH=CHCO 2 ) 6 (bpy) 2 ] (1) (bpy = 2,2-bipyridine), was synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic space group P1 with cell parameters: a = 11.347(6), b = 11.471(6), c = 14.247(8) Å , α = 69.503(9), β = 74.211(9), γ = 76.812(11)°, V = 1653.2(15) Å3, Z = 1, and R1(F) = 0.026, wR2(F 2 ) = 0.138. Complex 1 has a linear arrangement of three Co(II) centers bridged by six cinnamate carboxylate groups, four of which function in a bidentate syn-syn fashion linking the peripheral Co2 atoms, and two as both bidentate bridging and bidentate chelating units. The Co1 atom is located on a crystallographic inversion center and exhibits a slightly distorted octahedral coordination geometry, while the terminal Co atoms (Co2 and Co2 #1 ) have a significantly distorted octahedral environment. Hydrogen bonding interactions and π-π stacking interactions stabilize the structure

Two silver 5,5-diethylbarbiturate (barb) complexes with 2,2'-bipyridine (bpy) and 3-(2-pyridyl) propanol (pypr), [Ag(barb)(bpy)] (1) and [Ag(barb)(pypr)] (2), have been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single crystal X-ray diffraction. Both complexes crystallize in the triclinic space group P1 with Z = 2. The barb ligand in 1 is N-coordinated and the bpy ligand acts as a bichelating ligand leading to an AgN 3 tricoordination. Crystals of 1 feature a three-dimensional network based on N-H···O hydrogen bonding, π(bpy)···π(bpy), C-H···π(bpy) and π(bpy)-Ag interactions. In 2, the pypr and barb ligands behave as monodentate ligands through their N atoms, forming a distorted linear AgN 2 coordination. Molecules of 2 are doubly bridged by N-H···O hydrogen bonds and further connected via O-H···O hydrogen bonds and aromatic π(pypr)···π(pypr) stacking interactions into a supramolecular network. Both complexes exhibit similar thermal decomposition behavior in air. The first stage corresponds to removal of the co-ligands such as bpy or pypr while the degradation of the barb moiety occurs at higher temperatures to give Ag 2 O. Like the barb, bpy and pypr ligands, 2 does not show any significant antimicrobial activity, but 1 is active against bacteria and fungi

Two new complexes [Ag(sac)(aepip)] (1) and [Ag(sac)(hepip)] (2) have been obtained by the reaction of AgNO 3 with Na(sac)・2H 2 O (sac = saccharinate) in the presence of N-(2-aminoethyl)piperidine (aepip) and N-(2-hydroxyethyl)piperidine (hepip), and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the monoclinic space group C2 and triclinic space group P1, respectively. In both complexes, silver( I) is tricoordinated. The sac ligand is N-coordinated, while aepip and hepip behave as N-N and N-O bidentate chelating ligands, respectively. The pip rings of both aepip amd hepip ligands adopt typical ‘chair’ conformation. The individual molecules are linked into one-dimensional chains by two N-H···O hydrogen bonds in 1, and one O-H···O hydrogen bond in 2. TG-DTG curves illustrated that the endothermic elimination of aepip and hepip ligands takes place in the early stages of thermal decomposition, while that of the sac moiety occurs exothermically at higher temperatures to give metallic silver

A series of primary and secondary carboxyalkylcobalamins with (CH 2 ) n COOH groups (n = 1 - 3), CH 2 -CH(CH 3 )COOH, CH(R)COOH (R = CH 3 , C 2 H 5 , n-C 3 H 7 ), CH(CH 3 )(CH 2 )nCOOH (n = 1, 2) and CH(COOH)CH 2 COOH attached to cobalt were synthesized or generated in situ, mostly by the reaction of vitamin B 12s or hydridocobalamin with the respective α- or ω-substituted halocarboxylic acids and reactions with olefinic carboxylic or dicarboxylic acids. Their rates of decomposition and the activation parameters ΔG o≠ , ΔH o≠ and ΔS o≠ Co-C bond cleavage were determined spectrophotometrically in aqueous solutions at different pH values. Carboxyalkylcobalamins are generally more stable in solution than comparable unsubsitituted alkylcobalamins. In secondary 1-carboxyalkylcobalamins this is attributable primarily to the inductive effect and smaller size of the carboxyl group. The presence of the carboxyl group also strengthens the axial interactions of cobalt with the 5,6-dimethylbenzimidazole (DMBZ) ligand, as evidenced through measurements of the pK a of DMBZ in these organocobalamins. Although also susceptible to spontaneous (‘mechanochemical’) decomposition, carboxyalkylcobalamins can exist with significantly longer half-lives in their base-on forms than corresponding alkylcobalamins. Short-lived, but detectable spectroscopically in solution, is succinylcobalamin, the secondary dicarboxyalkylcobalamin with a CH(COOH)CH 2 COOH group attached to cobalt, a compound of interest as a model of a postulated intermediate in the coenzyme B 12 -dependent methylmalonyl-CoA-succinyl-CoA mutase reaction

Ab initio computations within the density functional theory are reported for the spin cross-over complex [Fe(btz) 2 (NCS) 2 ] (btz = 2.2'-bis-4.5-dihydrothiazine), where 3d 6 Fe II is characterized by high-spin (HS t 2g 4 , e g 2 ) and low-spin (LS t 2g 6 , e g 0 ) states. Results of infrared and Raman spectra for the isolated molecule are complemented for the crystalline solid with a full account of the electronic band structure properties: the density of states assessing the crystal field effects and the chemical bonding, assigning a specific role to the Fe-N interactions within the coordination sphere of Fe II

(dpp-BIAN)Mg(THF) 3 (1) (dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and (PhCOO) 2 react with splitting of the peroxide bridge and formation of the dimeric magnesium benzoate [(dpp-BIAN)MgOCOPh(THF)] 2 (2). The reaction of 1 with PhCOOH yields the dimeric magnesium benzoate [(dpp-BIAN)(H)MgOCOPh(THF)] 2 (3), whereas 1 and furanyl-2-carboxylic acid react with liberation of hydrogen and formation of (dpp-BIAN)Mg[OCO(2-C 4 H 3 O)]2 Mg(dpp-BIAN)(THF) (4). Compounds 2, 3, and 4 have been characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis, compound 3 also by 1 H NMR spectroscopy. The eightmembered metallacycles of the centrosymmetric dimers 2 and 3 are almost completely planar. The two magnesium atoms in 4 show different coordination spheres; one is surrounded by its ligands in a trigonal bipyramidal manner, the other one in a tetrahedral fashion. The Mg···Mg separations in 2, 3 and 4 are 4.236, 4.296, and 4.030 Å, respectively

The chiral β -diketimine ligand [(S)-Ph(Me)CH-N=C(Me)]CH 2 was prepared by condensation of acetylacetone with the commercially available chiral building block (S)-Ph(Me)CH-NH 2 . Reaction of bis(o-Me 2 N-α-Me 3 Si-benzyl)calcium with this β -diketimine led to double deprotonation. Reaction of bis(o-Me 2 N-α-Me 3 Si-benzyl)calcium with the commercially available chiral bis-oxazoline (S)-Ph-BOX gave diastereopure [(S)-Ph-BOX](o-Me 2 N-α-Me 3 Si-benzyl)calcium which in solution slowly decomposed with formation of o-Me 2 N-α-Me 3 Si-toluene. The corresponding amide complex [(S)-Ph-BOX]CaN(SiMe 3 ) 2 ·(THF)2 is stable and the crystal structure has been determined. In solution, this heteroleptic amide is in Schlenk equilibrium with the homoleptic species [(S)-Ph-BOX] 2 Ca and Ca[N(SiMe 3 ) 2 ] 2 ·(THF) 2 . This Schlenk equilibrium can be steered to the heteroleptic side. Use of the enantiopure calcium amide catalyst for the hydrosilylation of styrene with PhSiH3 or in the intramolecular hydroamination of aminoalkenes gave good product yields, but only small ee-values were observed (5 - 10%). From stoichiometric reactions of the catalyst with the substrates it is concluded that the “true” catalytically active species is mainly present as a homoleptic calcium complex, which explains the poor enantioselectivities

Keggin heteropoly acids supported on solids with different nature were used in the Biginelli reaction in order to obtain dihydropyrimidones. The results show that the activity of the catalysts is dependent on the supports used to obtain the catalysts. This method consistently has the advantages of excellent yield, mild reaction conditions, ease of workup, survival of different functional groups, and short reaction times

A Keggin-type arsenotungstate anion-supported iron-bipyridine complex, [Fe(2,2'-bipy) 3 ] 1.5 - [AsW VI 10 W V 2 O 40 Fe(2,2'-bipy) 2 (H 2 O)] · 0.25H 2 O, has been hydrothermally synthesized and characterized by IR and ESR spectra, TG-DTA analysis, and single crystal X-ray diffraction. Each structural unit of the title compound consists of one [AsW VI 10 W V 2 O 40 Fe(2,2'-bipy) 2 (H 2 O)] 3 − heteropolyanion, one and a half [Fe(2,2'-bipy) 3 ] 2+ cations, and a quarter of an H 2 O molecule. In the heteropolyanion the [Fe(2,2'-bipy) 2 (H 2 O)] 2+ unit is covalently bonded to the reduced Keggin polyoxoanion [AsW VI 10 W V 2 O 40 ] 5− . The complex ismonoclinic, space group C2/c with a = 46.8079(13), b = 14.3990(4), c = 26.1085(8) Å , β = 90.00(5)°, Z = 8, D c = 3.10 g/cm 3

A novel transition metal polyoxotungstate, [Cu(H 2 O) 6 ][{Cu(H 2 O) 2 } 2 {Cu(H 2 O) 4 H 4 W 12 O 42 }] · 12H 2 O (1), has been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV/vis spectroscopy, and TG analysis. The paradodecatungstate anions [H 2 W 12 O 42 ] 10− are linked by CuO 6 octahedra, forming a three-dimensional (3D) structure. The magnetic susceptibility of compound 1 in the temperature range 2 - 300 K shows the presence of antiferromagnetic interactions within the uniform Cu2・ ・ ・Cu3 chains

The high-temperature modification of LuAgSn was obtained by arc-melting an equiatomic mixture of the elements followed by quenching the melt on a water-cooled copper crucible. HT-LuAgSn crystallizes with the NdPtSb-type structure, space group P6 3 mc: a = 463.5(1), c = 723.2(1) pm, wR2 = 0.0270, 151 F 2 , and 11 variables. The silver and tin atoms build up two-dimensional, puckered [Ag 3 Sn 3 ] networks (276 pm Ag-Sn) that are charge-balanced and separated by the lutetium atoms. The Ag-Sn distances between the [Ag 3 Sn 3 ] layers of 294 pm are much longer. Single crystals of isotypic DyAgSn (a = 468.3(1), c = 734.4(1) pm, wR 2 = 0.0343, 411 F 2 , and 11 variables) and HoAgSn (a = 467.2(1), c = 731.7(2) pm, wR 2 = 0.0318, 330 F 2 , and 11 variables) were obtained from arc-melted samples. Under high-pressure (up to 12.2 GPa) and high-temperature (up to 1470 K) conditions, no transitions to a ZrNiAl-related phase have been observed for DyAgSn, HoAgSn, and YbAgSn. HT-TmAgSn shows Curie-Weiss paramagnetism with μ eff = 7.53(1) μ B /Tm atom and θ P = −15.0(5) K. No magnetic ordering was evident down to 3 K. HT-LuAgSn is a Pauli paramagnet. Room-temperature 119 Sn Mössbauer spectra of HT-TmAgSn and HT-LuAgSn show singlet resonances with isomer shifts of 1.78(1) and 1.72(1) mm/s, respectively

The origins and development of the electronegativity concept as an empirical construct are briefly examined, emphasizing the confusion that exists over the appropriate units in which to express this quantity. It is shown how to relate the most reliable of the empirical scales to the theoretical definition of electronegativity in terms of the quantum potential and ionization radius of the atomic valence state. The theory reflects not only the periodicity of the empirical scales, but also accounts for the related thermochemical data and serves as a basis for the calculation of interatomic interaction within molecules. The intuitive theory that relates electronegativity to the average of ionization energy and electron affinity is elucidated for the first time and used to estimate the electron affinities of those elements for which no experimental measurement is possible

A convenient synthesis of 4-substituted 2-(3-hydroxy-2-oxo-1-phenethylpropylcarbamoyl)pyrrolidine- 1-carboxylic acid benzyl esters 17 and 18 as new cysteine protease inhibitors is described. The synthetic key strategies involve the diazocarbonyl insertion reaction of N-Boc-L-homophenylalanine (1) by diazomethane, acetylation of the bromoketone 2 with sodium acetate, and condensation of acids 12, 14 with (3S)-3-amino-2-oxo-5-phenyl-pentyl acetate monohydrochloride (4) in good yield

A variety of aminoazoles were reacted with bidentate electrophiles producing azolopyrimidines. The regioselectivity of the nucleophilic attack could be defined from the 13 C chemical shift of the pyrimidine carbons and through NOE experiments

One-pot syntheses of various 4-aryl-5-imino-3-phenyl-1H-naphtho[2,3- f ]-1,2,4-triazepine-6,11- diones 5a - f via reaction of amidrazones 1a - f with 1,4-dioxo-1,4-dihydronaphthalene-2,3- dicarbonitrile (4) are reported