Die Berechnung von Einelektronen-Integralen in der SCF-Xα-SW-Methode: I. Die Normierung

A normalization of the wave functions by means of the theoretical exact Multiple-Scattering-(MS)-formalism is discussed within the framework of the SCF-X-SW-method. For the atomic and extramolecular regions the integrals of normalization can be easily determined and the results can be described by the corresponding electronic charges. The calculation of the integral of the interatomic region is problematic. The needful volume integration is only necessary to theGreen's functions of the wave functions and can be solved by means of the residual theory. The further analytical calculation of the surface integrals leads to a complicated formalism which can be numerically evaluated.

     

Synthesis and structural assignment of some N-substituted imidazopyridine derivatives

A synthesis of all possible N-alkylated 2-n-butyl-imidazo[4,5]pyridine isomers is described as well as their structural assignment by ¹H NMR spectroscopy. One of these derivatives, 2,-n-butyl-3-[2′- (1H-tetrazol-5-yl)-4-biphenylylmethyl]-3H-imidazo[4,5-b]pyridine 9 is a potent angiotensin II receptor antagonist.     

Untersuchungen zur reaktivität von metall-π-komplexen : XVIII. Elektrophile und nucleophile additionsreaktionen an siebenringliganden in tricarbonylmolybdän-komplexen: Synthese von [C7H9Mo(CO)3]BF4, C7H9Mo(CO)3Cl und [C7H9P(C6H5)3]BF4

C₇H₈Mo(CO)₃ reacts with HBF₄ and HCl by protonation of the ring ligand and formation of [C₇H₉Mo(CO)₃]BF₄ (I) and C₇H₉Mo(CO)₃Cl (II), respectively. The compounds are characterised by means of their IR and NMR data. The reaction of I with P(C₆H₅)₃ does not lead, as expected, to [C₇H₉Mo(CO)₃P(C₆H₅)₃]BF₄ (III) but to the phosphonium salt [C₇H₉P(C₆H₅)₃]BF₄ (IV), i.e. nucleophilic addition of the phosphine at the cycloheptadienyl group takes place. The structure of IV has been determined by ¹³C NMR measurements.     

Fluorine-Containing Organozinc Reagents Part 1 A Simple Synthesis of 2,2-Dichloro-3,3,3-trifluoropropanol

The title compound 1 , which can be regarded as a synthetic equivalent of substituted 1,1,1-trifluoroacetone 2 , is prepared by Zn-induced reductive addition of 1,1,1-trichloro-2,2,2-trifluoroethane ( 3 ) to formaldehyde ( 4 ). A brief survey of the scope of this C? C-bond formation leading to a variety of new CF₃-containing synthetic building blocks is also given.     

Pseudohalogenometallverbindungen: LVIII. Reaktionen von diphenylphosphorylazid und perfluor-n-hexylsulfonylazid mit triphenylphosphan-komplexen von platin(0), rhodium(I), iridium(I), ruthenium(0), kobalt(II) und kupfer(I)

Diphenylphosphorylazide N₃P(O)(OPh)₂ reacts with Pt(PPh₃)₃, Pt(PPh₃)₂(C₂H₄), trans-RhCl(CO)(PPh₃)₂, Ru(CO)₃(PPh₃)₂, CoCl₂(PPh₃)₂ and CuCl(PPh₃)₂ to give the azido complexes Pt(PPh₃)₂(N₃)R, Pt(PPh₃)₂(N₃)₂R₂, the urylene complex RhCl(PPh₃)₂(RNCONR) and the phosphine imine complexes Ru(CO)₃(RPPh₃)₂, CoCl₂(RNPPh₃)₂, CuCl(RNPPh₃)₂, respectively, (RP(O)(OPh)₂). The oxidative addition of n-C₆F₁₃SO₂N₃ to Pt(PPh₃)₄ and Pt(PPh₃)₂(C₂H₄) affords the complexes Pt(PPh₃)₂(N₃)R and Pt(PPh₃)₂(N₃)₂R₂, respectively, (RSO₂C₆F₁₃. The compounds are characterized by elemental analysis and by their IR spectra.     

Adducts of organogallium chlorides with hydrazines and the formation of dimeric dialkylgallium hydrazides possessing different ring sizes

The dialkylgallium chlorides R₂GaCl (R = Me, Et, CMe₃) reacted with hydrazines H₂N-N(H)R′ (R′ = CMe₃, C₆H₅) to form the adducts R₂ClGa ← NH₂-N(H)R′ (1-4), in which the gallium atoms are coordinated by the NH₂ nitrogen atoms of the hydrazine ligands. Treatment of these adducts with tert-butyllithium as a base afforded dialkylgallium hydrazides (R₂Ga-N₂H₂R′)₂ [5 (R = R′ = CMe₃) and 6 (R = CMe₃, R′ = C₆H₅)] by deprotonation of the hydrazine ligands and precipitation of LiCl in two cases only. The remaining adducts gave a substitution reaction at gallium or an unclear reaction course. The hydrazides 5 and 6 adopt different structures in the solid state. The tri(tert-butyl) compound 5 possesses a four-membered Ga₂N₂ heterocycle in its molecular core with two exocyclic N-N bonds, which represents the structural motif usually observed for dialkylgallium hydrazides. 6 has a five-membered Ga₂N₃ heterocycle with one endocyclic and one exocyclic N-N bond. That structure is preserved in solution as clearly shown by NMR spectroscopy. The behaviour of 5 in solution is more complicated, which may be caused by cis/trans isomerization.     

Strong cooperativeness in the mononuclear iron(II) derivative exhibiting an abrupt spin transition above 400 K

The spin crossover system, [Fe(bzimpy)(2)](ClO(4))(2).0.25H(2)O, was reinvestigated above room temperature (bzimpy = 2,6-bis(benzimidazol-2-yl)pyridine). The system exhibits an abrupt low-spin to high-spin transition at T(c) = 403 K. Liberation of a fractional amount of water does not affect the spin crossover: the system is perfectly reversible with a hysteresis width of DeltaT = 12 K. The existence of the hysteresis at such high temperature determines that the lowest limit of the solid-state cooperativity parameter is J/k > 403 K despite long iron(II) separations (10 A). The high cooperativeness has been assigned to a perfect pi-stacking of the benzimidazole rings in the crystal lattice at a distance as short as 3.6 A. Variable-temperature IR data and the heat capacity measurements match well the magnetic data. The thermodynamic properties are DeltaH = 17 kJ mol(-)(1), DeltaS = 43 J K(-)(1) mol(-)(1), so that the entropy of the spin transition shows a considerable contribution from the molecular vibrations. A theoretical model has been applied in fitting the magnetic data along the whole hysteresis path. A statistical distribution of the cooperativity parameter led to the feature that angled walls of the hysteresis loop are well reproduced.     

Minimization of empirical energy functions in proteins including hydrophobic surface area effects

We present analytical expressions to calculate the gradient of the water-accessible surface area of proteins with respect to Cartesian coordinates and dihedral angles. A detailed mathematical analysis leads to corrected equations for the gradient calculation used previously in the ANAREA program. To study the hydrophobic effect of solvent-protein interactions, our expressions have been implemented to further improve the program package FANTOM. We used this version of FANTOM to minimize the ECEPP/2 and the hydrophobic energy of tendamistat. © 1993 John Wiley & Sons, Inc.     

‘Lone pair’ Electronic Structure,Conformation and Oxidation Behaviour of Diaziridines

Photoelectron spectroscopic investigations indicate that (i) monocyclic diaziridines prefer a trans-conformation of the nitrogen-lone pairs, and (ii) the interaction between these is comparable to that exhibited by open-chain analogues, i.e. alkyl-substituted hydrazines. The chemical experience concerning the particular case of ? NH? NH? →? N?N? oxidation of diaziridines can therefore not be accounted for by a prevailing unfavorable ‘lone pair’ interaction. Thermochemical as well as entropy arguments may serve as an explanation. A rather unsatisfactory agreement between predictions from various theoretical procedures and experimental results for the ionization potentials of ‘lone pair’ MO electrons is noted.