Solid State Structure of 2,2,4,4,6,6-Hexa(β-naphthyloxo)cyclophosphazatriene and Dipole Moments of Hexa(aryloxo)cyclophosphazatrienes

The crystal and molecular structure of [NP(OC10H7)2]3 was determined by X-ray analysis. The dipole moments of this compound and of the hexa(phenoxo)cyclotriphosphazatrienes of formula [NP(OC6H3XX′Y)2]3 (X = X′ = H, Y = p-Br; X = m-CH3,. X′ = H. Y = p-Cl; X = X′ = m-CH3, Y = p-Cl; X = X′ = m-CH3, Y = H; X = X′ = H, Y = p-CH(CH3)2; X = X′ = H, Y = p-C(CH3)3) were measured in benzene at 25°C. Crystals of [NP(OC10H7)2]3 are monoclinic with unit cell dimensions a = 24.870(15), b = 7.712(8), c = 27.687(14) Å, β = 115.85(7)°; space group P21/c. The structure was refined to an agreement factor of 0.09. The phosphazene ring deviates (max. deviation 17°) from planarity. and mean distances (A) and angles (°) are P-N 1.58(1). P-O 1.58(1), O-C 1.41(2); P-N-P 120(1), N-P-N 119(1), P-O-C 124(2). The conformations of the naphthyloxo groups at P(2) and P(3) are similar, and different from the group at P(1). Dipole moment analysis showed that the solid state conformation changes in the solution state. The measured value was in agreement with a symmetric conformation in which at the O-P-O plane each naphthyloxo group is rotated by ca. 40-50° from the anti-coplanar arrangement relative to this plane. The dipole moment data for the p-substituted phenoxo derivatives agree with such a conformation, but the analysis of the dipole moment values of phosphazenes having phenoxo groups bearing more than one substituent group and p-CH(CH3)2 substituent failed to do so due to the inherent limitations of the method

Synthesis and structural characterization of new oxorhenium and oxotechnetium complexes with XN2S-tetradentate semi-rigid ligands(X = O, S, N)

Twelve novel oxo-technetium and oxo-rhenium complexes based on N2S2-, N2SO- or N3S-tetradentate semi-rigid ligands have been synthesised and studied herein. By reacting the ligands with a slight excess of suitable [MO]3+ precursor (ReOCl3(PPh3)2 or [NBu4][99gTcOCl4]), the monoanionic complexes of general formula [MO(Ph–XN2S)]− could be easily produced in high yield. The complexes have been characterized by means of IR, electrospray mass spectrometry, elemental analysis, NMR and conductimetry. The crystal structures of [PPh4][ReO(Ph–ON2S)] 1b and [NBu4][99gTcO(Ph–ON2S)] 1c have been established. The [MO]3+ moiety was coordinated via the two deprotonated amide nitrogens, the oxygen and the terminal sulfur atoms in 1b and 1c. In both compounds, the ON2S coordination set is in the equatorial plane, and the complexes adopted a distorted square-pyramidal geometry with an axial oxo-group. The chemical and structural identity of the different prototypic complexes (rhenium, 99gTc complexes and their corresponding 99mTc radiocomplexes) have been also established by a comparative HPLC study

Solid-state structure of 2,6-dimethyl-gamma-pyrone

2,6-dimethyl-4H-pyranylidene-4-one, shortly 2,6- dimethyl-y-pyrone, is a widely known chemical reagent used in the synthesis of various heterocycles. A contin uous quest is being carried out in our research group for metal ligands; the title compound was taken for examination due to its ability of coordinating transition elements, in particular lanthanoids

Ligating ability of 1,1 '-bis(diphenylphosphino)ferrocene: a structural survey (1994-1998)

This paper outlines the ligating ability of 1,1'-bis(diphenylphosphino) ferrocene. The focus is on the extensive coordination chemistry exhibited by this ligand to transition metals. The structural parameters of mono-, bi- and polynuclear species are reviewed and simple relationships between some of these parameters are reported and discussed. The review mainly covers the X-ray structure determinations published over the 1994-98 period. (C) 2000 Elsevier Science B.V. All rights reserved

Molecular modeling, theoretical calculations and property evaluation of three muscarinic agonists, X-ray structures of LU 25-109 and WAL 2014

LU 25-109 (II) and WAL 2014 (talsaclidine, III) are two M1 muscarinic agonists chemically related to the natural substance arecoline (I). All these compounds have beneficial effects on memory and cognition in animals and humans, and they have been proposed in the treatment of Alzheimer's disease, but only III will likely find a place in therapy. In this work we have investigated the solid state structures of II and III and the X-ray structures of the two molecules and of the parent compound I have been used to input a series of computational chemistry efforts. In particular, the X-ray geometries have been manipulated to model 20 molecular structures (1-20) which have been submitted to ab initio, semiempirical quantum mechanics and molecular mechanics calculations. The conformational space accessible to the 20 structures has been assessed by means of potential energy maps. The reactivities of 1-20 have been estimated by examining at the graphics terminal the composition and the extension of the frontier orbitals (HOMOs and LUMOs) and of the molecular electrostatic potential. The information obtained has been interpreted to explain the different degrees of activity shown by I-III. Our data indicate that III has better in vivo activity for its intermediate size, less polar surface, conformational rigidity and orientation of reactive domains. (C) 2000 Elsevier Science B.V. All rights reserved

Chimica di Base

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Hydroxo and oxo complexes of platinum(II) stabilized by phosphanes: Synthesis and characterization - X-ray structures of cis-[L2Pt(mu-OH)](2)(NO3)(2) (L = PMe2Ph, PMePh2) and [{cis-(PMe2Ph)(2)Pt}(3)(mu-O)(2)]Cl-2

The dinuclear hydroxo complexes cis- [L2Pt(mu-OH)](2)(NO3)(2) (L = PMe2Ph and PMePh2) have been characterized by single-crystal X-ray analysis, and their reactivity towards chloride ions has been investigated. Reaction of cis-[L2Pt(mu-OH)](2)X-2 (L = PMe3, PMe2Ph; X = NO3-, CIO4-) with (NEt4)CI.H2O or (AsPh4)CI, in a 1:2 molar ratio, afforded a mixture of cis-[L2PtCl2] and [{cis-L(2)pt}(3)(mu-O)(2)](2+) in ca. equimolar amounts. The trinuclear oxo compounds, separated by fractional crystallization of the reaction mixtures, were fully characterized by spectroscopic techniques, and the derivative [(cis-(PMe2Ph)(2)Pt)(3)(mu-O)(2)]CI2 was also characterized by X-ray diffraction methods. Under the same experimental conditions, the structurally analogous hydroxo complex, stabilized by the less basic and more hindered PMePh2 ligand, reacted with Cl- to give cis-[(PMePh2)(2)PtCl2] as the only isolable species. The P-31 NMR spectroscopic analysis of the reaction mixtures allowed the detection of a moderately stable product, which is most likely to be the neutral hydroxo complex cis-[L2PtCl(OH)]

Hydroxo and Oxo Complexes of Platinum(II) Stabilized by Phosphanes: Synthesis and Characterization− X-ray Structures ofcis-[L2Pt(μ-OH)]2(NO3)2 (L = PMe2Ph, PMePh2) and [{cis-(PMe2Ph)2Pt}3(μ-O)2]Cl2

The dinuclear hydroxo complexes cis- [L2Pt(mu-OH)](2)(NO3)(2) (L = PMe2Ph and PMePh2) have been characterized by single-crystal X-ray analysis, and their reactivity towards chloride ions has been investigated. Reaction of cis-[L2Pt(mu-OH)](2)X-2 (L = PMe3, PMe2Ph; X = NO3-, CIO4-) with (NEt4)CI.H2O or (AsPh4)CI, in a 1:2 molar ratio, afforded a mixture of cis-[L2PtCl2] and [{cis-L(2)pt}(3)(mu-O)(2)](2+) in ca. equimolar amounts. The trinuclear oxo compounds, separated by fractional crystallization of the reaction mixtures, were fully characterized by spectroscopic techniques, and the derivative [(cis-(PMe2Ph)(2)Pt)(3)(mu-O)(2)]CI2 was also characterized by X-ray diffraction methods. Under the same experimental conditions, the structurally analogous hydroxo complex, stabilized by the less basic and more hindered PMePh2 ligand, reacted with Cl- to give cis-[(PMePh2)(2)PtCl2] as the only isolable species. The P-31 NMR spectroscopic analysis of the reaction mixtures allowed the detection of a moderately stable product, which is most likely to be the neutral hydroxo complex cis-[L2PtCl(OH)]

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