Solvent-Induced Bond-Bending Isomerism in Hexaphenyl Carbodiphosphorane: Decisive Dispersion Interactions in the Solid State.

Previous reports in the literature describe that the crystallization of hexaphenyl carbodiphosphorane (CDPPh) from a variety of solvents gives a "bent" geometry for the P-C-P moiety as the solid-state molecular structure. However, a linear structure is observed when CDPPh is crystallized from benzene. Here, we report detailed spectroscopic and theoretical studies on the linear and bent structures. X-ray powder diffraction examinations show a phase transition of linear CDPPh upon the loss of co-crystallized benzene molecules, which is accompanied by the bending of the P-C-P unit. Studies on the linear and bent structures (i.e., X-ray powder diffraction, solid-state NMR, UV-vis spectroscopy, and IR spectroscopy) show significant differences in their properties. Investigations of the solid-state structures with density functional theory-based methods (PBE-D3) point toward subtle dispersion effects being responsible for this solvent-induced bond-bending isomerism in CDPPh.

Double donation in trigonal planar iron-carbodiphosphorane complexes - a concise study on their spectroscopic and electronic properties.

We present the syntheses of trigonal planar coordinated Fe(ii) carbodiphosphorane (CDPR) complexes, starting from iron(ii)-bis(trimethylsilylamide) [Fe{N(SiMe3)2}2] and hexaphenyl-(CDPPh) and sym-dimethyltetraphenyl-carbodiphosphoranes (CDPMe), respectively. Both complexes [CDPPh-Fe{N(SiMe3)2}2] (1) and [CDPMe-Fe{N(SiMe3)2}2] (2) were examined in solution and in the solid state. 1 shows a dissociation equilibrium in solution which we monitored by variable temperature 1H-NMR spectroscopy. Magnetic measurements of 1 and 2 yielded a high spin configuration (S = 2) for both complexes. Quantum chemical calculations were performed to analyze the bonding situation in compound 1.

Hexaphenyl carbodiphosphorane adducts of heavier group 15 element trichlorides: syntheses, properties and reactivities.

Herein, we present a series of hexaphenyl carbodiphosphorane (CDPPh) adducts of heavier group 15 trichlorides ECl3 (E = P-Bi). The reaction with PCl3 yields the known salt [CDPPh-PCl2][Cl] ([1][Cl]), the heavier element trichlorides ECl3 (E = Sb (4), Bi (5)) give the neutral adducts CDPPh-ECl3 which were characterised crystallographically and spectroscopically. The reaction of CDPPh with AsCl3 does not yield CDPPh-AsCl3 (2), but in the presence of GaCl3 the corresponding salt [CDPPh-AsCl2][GaCl4] ([3][GaCl4]) is formed. DFT (density functional theory) calculations were carried out to examine the molecular frontier orbitals in 1+-5. Additional reactivity studies revealed an intramolecular electrophilic aromatic substitution (SEAr) in 1+, which represents an excellent starting point for further selective C-P bond formation reactions.

Proton Affinities of Cationic Carbone Adducts [AC(PPh3 )2 ](+) (A=Halogen, Hydrogen, Methyl) and Unusual Electronic Structures of the Cations and Dications [AC(H)(PPh3 )2 ](2.).

This work reports the syntheses and the first crystal structures of the cationic carbone adducts [FC(PPh3 )2 ](+) and [BrC(PPh3 )2 ](+) and the protonated dication [FC(H)(PPh3 )2 ](2+) , which are derived from the carbone C(PPh3 )2 . Quantum chemical calculations and bonding analyses were carried out for the series of cations [AC(PPh3 )2 ](+) and dications [AC(H)(PPh3 )2 ](2+) , where A=H, Me, F, Cl, Br, I. The bonding analysis suggests that the cations are best described as phosphane complexes L→(CA)(+) ←L (L=PPh3 ), which are related to the neutral borylene adducts L→(BA)←L (L=cyclic carbene; A=H, aryl) that were recently isolated. The carbone adducts [AC(PPh3 )2 ](+) possess a π electron lone pair at carbon and they can easily be protonated to the dications [AC(H)(PPh3 )2 ](2+) . The calculations of the dications indicate that the molecules are best represented as complexes L→(CHA)(2+) ←L (L=PPh3 ) where a carbene dication is stabilized by the ligands. The central carbon atom in the cations and even in the dications carries a negative partial charge, which is larger than the negative charge at fluorine. There is also the peculiar situation in which the carbon-fluorine bonds in [FC(PPh3 )2 ](+) and [FC(H)(PPh3 )2 ](2+) exhibit the expected polarity with the negative end at fluorine, but the carbon atom has a larger negative charge than fluorine. Given the similarity of carbodiphosphorane C(PPh3 )2 and carbodicarbene C(NHC)2 , we expect that analogous compounds [AC(NHC)2 ](+) and [AC(H)(NHC)2 ](2+) with similar features as [AC(PPh3 )2 ](+) and [AC(H)(PPh3 )2 ](2+) can be isolated.

Two new neutral copper(II) complexes with dipicolinic acid and 3-amino-1H-1,2,4-triazole formed under different reaction conditions: synthesis, characterization, molecular structures and DNA-binding studies.

Two Cu(II) complexes, [Cu2(µ-atr)(pydc)2(H2O)4]·5H2O (1) and [Cu(atr)(pydc) (H2O)]·H2O (2), with pyridine-2,6-dicarboxylic acid (H2pydc) and 3-amino-1H-1,2,4-triazole (atr), have been synthesized and characterized. The interaction ability of the both complexes with native calf thymus DNA (CT-DNA) has been monitored as a function of the metal complex-DNA molar ratio. UV-vis spectrophotometry, circular dichroism (CD), thermal denaturation studies, cyclic voltammetry (CV) and viscosity measurements. The intrinsic binding constants K(b) of complexes 1 and 2, with CT-DNA obtained from UV-vis absorption studies were 4.7 (±0. 1) × 10(4) and 9.5 (±0. 1) × 10(4) M(-1), respectively. Further investigation of interaction mode was performed using viscosity, cyclic voltammetry and T(m) of CT-DNA studies as well as CD study, indicating complexes bind to DNA via an intercalation mode.

Exploiting the Twofold Donor Ability of Carbodiphosphoranes: Theoretical Studies of [(PPh3 )2 C→EH2 ]q (Eq =Be, B+ , C2+ , N3+ , O4+ ) and Synthesis of the Dication [(Ph3 P)2 CCH2 ]2.

Quantum chemical calculations at the BP86/TZVPP//BP86/SVP level of theory have been performed for the isoelectronic series of compounds [(PPh3 )2 C→EH2 ]q (Eq =Be, B+ , C2+ , N3+ , O4+ ). The equilibrium geometries and bond dissociation energies were calculated and the nature of the C→E bond was investigated with charge and energy decomposition methods. The dication [(PPh3 )2 C→CH2 ]2+ could become isolated as a salt compound with two counter ions [AlBr4 ]- . The X-ray structure analysis of [(PPh3 )2 C→CH2 ]2+ gave bond lengths and angles that are in good agreement with the calculated data. The geometry optimization of [(PPh3 )2 C→OH2 ]4+ gave [(PPh3 )2 C→OH]3+ as the equilibrium structure. Bonding analysis of [(PPh3 )2 C→EH2 ]q shows that [(PPh3 )2 C→BeH2 ] and [(PPh3 )2 C→BH2 ]+ possess donor-acceptor bonds in which the σ and π lone-pair electrons of (PPh3 )2 C donate into the vacant orbitals of the acceptor fragment. The multiply charged compounds are better described as substituted olefins [(PPh3 )2 CCH2 ]2+ , [(PPh3 )2 CNH2 ]3+ , and [(PPh3 )2 COH]3+ , which possess electron-sharing σ and π bonds that arise from the interaction between the triplet states of [(PPh3 )2 C]2+ and the respective fragment CH2 , (NH2 )+ , and (OH)+ . The multiply charged cations [(PPh3 )2 CCH2 ]2+ , [(PPh3 )2 CNH2 ]3+ , and [(PPh3 )2 COH]3+ are calculated to be stable toward dissociation.

(E)-4-(2-Hy-droxy-3-meth-oxy-benzyl-idene-amino)-6-methyl-3-sulfanyl-idene-3,4-dihydro-1,2,4-triazin-5(2H)-one.

In the title mol-ecule, C(12)H(12)N(4)O(3)S, there is an intra-molecular O-H⋯N hydrogen bond. The dihedral angle between the benzene and triazine rings is 65.9 (3)°. In the crystal, N-H⋯S and O-H⋯N hydrogen bonds link the mol-ecules into chains along [010]. In addition, there are weak π-π stacking inter-actions between symmetry-related triazine rings with a centroid-centroid distance of 3.560 (3)°.

4-Methyl-N-[(E)-4-methyl-1-(4-methyl-phenyl-sulfon-yl)-1,2-dihydropyridin-2-yl-idene]benzene-sulfonamide.

The reaction of 2-(amino-meth-yl)pyridine and 4-toluene-sulfonyl chloride in CH(2)Cl(2) at pH 8 led to the title compound, C(20)H(20)N(2)O(4)S(2). The aromatic rings are almost perpendicular to each other and the dihedral angles between the aromatic ring planes are 74.33 (9) (central pyridine versus benzene ring of the tosyl group bonded to the imine functionality), 73.77 (6) (pyridine versus benzene ring of the tosyl group bonded to pyridinic N atom) and 79.83 (9)° (benzene rings of tosyl groups). In the crystal structure, inter-molecular aromatic π-π stacking inter-actions [centroid-centroid separation = 3.6274 (14) Å] help to consolidate the packing.

Reaction of [Fe2(CO)8(mu-CF2)] with AsMe3 and other Lewis bases: syntheses, crystal structures of [Fe(CO)6(AsMe3)2(mu-CF2)] and [Fe(CO)5(AsMe3)3(mu-CF2)], and theoretical considerations.

The difluorcarbene complex [Fe2(CO)8(mu-CF2)] (2) reacts with AsMe3 under CO substitution to give the mu-CF2 containing complexes [Fe2(CO)6(AsMe3)2(mu-CF2)] (4) and [Fe2(CO)5(AsMe3)3(mu-CF2)] (5) which have an [Fe2(CO)9]-like structure as shown by X-ray analyses. In the solid state, 4 forms two isomers, 4a and 4b, in a 3 to 1 ratio, which differ in the position of the mu-CF(2) ligand; 4a has a local C(2) axis and 4b has C1 symmetry. The Fe-Fe distances in 4 and 5 are 2.47 A and are the shortest ones found in [Fe2(CO)9]-like compounds. Efforts were also undertaken to replace one or more CO groups in 2 by other ligands, such as N (bpy, phen, pzy, etc.) or P donors (dppe, dppm). With dppm, only the CF(2) free complex, [Fe2(CO)4(mu-Ph2PCH2PPh2)2(mu-CO)] (6), could be detected and characterized by X-ray analysis. Most of the reactions resulted in the formation of red-brown materials which were insoluble in the usual solvents and which could not be characterized. The use of CH2Cl2 during the attempts to crystallize a product from the reaction of 2 and phen gave [Fe(phen)3]Cl2 (7) in low yields. For 4 and 5, the electronic structures were analyzed using the atoms in molecules (AIM) theory. No electron density was found between the two iron atoms, and the short contacts can be interpreted in terms of a pi-interaction.

Experimental and theoretical studies of carbodiphosphorane-CX2 adducts with unusual bonding situations: preparation, crystal structures, and bonding analyses of S2CC(PPh3)2, O2CC(PPh3)2, and [(CO)4MS2CC(PPh3)2] (M = Cr, Mo, W).

We report about the first X-ray structure analyses of the CS2 and CO2 adducts with carbodiphosphorane C(PPh3)2 and the synthesis and X-ray structure analysis of group 6 carbonyl complexes with compound S2CC(PPh3)2 as a ligand [(CO)4MS2CC(PPh3)2] (M = Cr, Mo, W). The nature of the carbon-carbon bonding in X2CC(PPh3)2 and in the model compounds X2CC(PH3)2 and the metal-ligand bonding in [(CO)4MoS2CC(PH3)2] have been analyzed with charge and energy decomposition methods using DFT calculations. Carbodiphosphoranes C(PR3)2 are double electron pair donors having sigma- and pi-carbon lone-pair orbitals as the two highest occupied MOs.

Organometallic sesquialkoxides of aluminium, gallium and indium.

Organometallic sesquihalides of aluminium are important intermediates in technical processes. However, those compounds and their homologues with gallium or indium centers have not been structurally characterized so far. On the other hand organometallic sesquialkoxides have been isolated. The major synthetic routes and the structures of the corresponding products will be discussed. Furthermore, cage-contructiveness reactions having sesquialkoxides as educts will be shown. Discussion will focus primarily on the syntheses, the spectroscopic findings and a structural comparison. Especially the structural motifs deserve attention because of the structural connection to the well-known earth metal alkoxides.

Enantioselective Norrish-Yang cyclization reactions of N-(omega-oxo-omega-phenylalkyl)-substituted imidazolidinones in solution and in the solid state.

The four N-(omega-oxo-omega-phenyl-alkyl)-substituted imidazolidinones 5-8 were prepared from N-acetylimidazolidinone (4). Upon irradiation, these substrates underwent Norrish-Yang cyclization to the racemic products rac-9-rac-12 (51-75%). The reactions of the N-2-oxoethylimidazolidinones 5 and 6 were conducted in tBuOH, and yielded 1:1 mixtures of exo/endo diastereoisomers rac-9a/rac-9b and rac-10a/rac-10b, accompanied by Norrish type II cleavage products. The reactions of the N-3-oxopropylimidazolidinones 7 and 8 were performed in toluene. The exo diastereoisomers rac-11a and rac-12a were the major diastereoisomers (d.r. approximately equal to 4:1). In the presence of the chiral compounds 1-3, the photocyclization of substrate 8 proceeded with significant enantiomeric excess (5-60% ee). The more sophisticated complexing agents 3 and ent-3 provided better enantiofacial differentiation (up to 60% ee) than the lactams 1 and 2 (up to 26% ee). Low temperatures and an excess of the complexing agent helped to increase the enantioselectivity. The absolute configuration of the major exo product 12a obtained from compound 8 in the presence of complexing agent 3 was unambiguously established by single-crystal X-ray crystallography of its chiral N-methoxyphenylacetyl derivative 15a. In a similar fashion, the absolute configurations of the endo products 12b and ent-12b were established. The N-2-oxoethylimidazolidinone 5, which crystallized in a chiral space group, was irradiated in the solid state. At low levels of conversion, the product 9a/ent-9a was formed with high enantiomeric excess (78% ee). The enantioselectivity deteriorated at higher levels of conversion.

[Te6 N8 (TeCl4 )4 ]-Tellurium Nitride Stabilized by Tellurium Tetrachloride.

Shielding by four TeCl4 molecules is observed for the distorted rhombic dodecahedron core of the tellurium nitride Te6 N8 (see picture). With the characterization of this structure, the composition of the tellurium nitride discovered 100 years ago has now been determined. As a result of the shielding effect, the explosive character of the nitride is lost.