Conformation-Associated C···dz2-PtII Tetrel Bonding: The Case of Cyclometallated Platinum(II) Complex with 4-Cyanopyridyl Urea Ligand

The nucleophilic addition of 3-(4-cyanopyridin-2-yl)-1,1-dimethylurea (1) to cis-[Pt(CNXyl)2Cl2] (2) gave a new cyclometallated compound 3. It was characterized by NMR spectroscopy (1H, 13C, 195Pt) and high-resolution mass spectrometry, as well as crystallized to obtain two crystalline forms (3 and 3·2MeCN), whose structures were determined by X-ray diffraction. In the crystalline structure of 3, two conformers (3A and 3B) were identified, while the structure 3·2MeCN had only one conformer 3A. The conformers differed by orientation of the N,N-dimethylcarbamoyl moiety relative to the metallacycle plane. In both crystals 3 and 3·2MeCN, the molecules of the Pt(II) complex are associated into supramolecular dimers, either {3A}2 or {3B}2, via stacking interactions between the planes of two metal centers, which are additionally supported by hydrogen bonding. The theoretical consideration, utilizing a number of computational approaches, demonstrates that the C···dz2(Pt) interaction makes a significant contribution in the total stacking forces in the geometrically optimized dimer [3A]2 and reveals the dz2(Pt)→π*(PyCN) charge transfer (CT). The presence of such CT process allowed for marking the C···Pt contact as a new example of a rare studied phenomenon, namely, tetrel bonding, in which the metal site acts as a Lewis base (an acceptor of noncovalent interaction).

Evaluation of Concomitant Halogen and Pnictogen Bonds in Cocrystals of Imines Derived from 2-Nitrobenzaldehyde and 4-Haloaniline

Three imines have been prepared by condensation of 2-nitrobenzaldehyde and 4-haloanilines (halo = Cl, Br, and I) with functionalities that enabled them to act as both halogen and pnictogen bond donors; however, both interactions were found to be absent in the solid state. The prepared imines were further cocrystallized with 1,3-diiodotetrafluorobenzene and 1,3,5-triiodotetrafluorobenzene as halogen bond donors. Six novel cocrystals were prepared by means of liquid-assisted mechanochemical synthesis and by crystallization from solution. All six cocrystals were of 1:1 stoichiometry and comprised a N···I halogen bond between an iodine atom of the perhalogenated halogen bond donor and the imino nitrogen atom of the imine acting as an acceptor. Additionally, in all six cocrystals, the imine molecules were interconnected by NO2···NO2 pnictogen bonding interactions. Computational analysis has shown that the NO2···NO2 exhibits bond critical point electron densities in the region (4.897-8.306) × 10-3 e Å-3 and interaction energies of 23.6-27.7 kJ mol-1, whereas the N···I halogen bonds generally have higher critical point electron densities ((1.795-1.937) × 10-2 e Å-3), but the corresponding total interaction energies are lower (19.4-20.4 kJ mol-1). Statistical analysis of the appearance of NO2···NO2 contacts concomitantly with halogen or hydrogen bonds seems to indicate that there is a positive correlation between the presence of NO2···NO2 pnictogen bonding interactions and other directional interactions in crystal structures.

Dissolution mechanism of cellulose in a benzyltriethylammonium/urea deep eutectic solvent (DES): DFT-quantum modeling, molecular dynamics and experimental investigation

In this paper, a benzyltriethylammonium/urea DES was investigated as a new green and eco-friendly medium for the progress of organic chemical reactions, particularly the dissolution and the functionalization of cellulose. In this regard, the viscosity-average molecular weight of cellulose (M̄w) during the dissolution/regeneration process was investigated, showing no significant degradation of the polymer chains. Moreover, X-ray diffraction patterns indicated that the cellulose dissolution process in the BTEAB/urea DES decreased the crystallinity index from 87% to 75%, and there was no effect on type I cellulose polymorphism. However, a drastic impact of the cosolvents (water and DMSO) on the melting point of the DES was observed. Besides, to understand the evolution of cellulose-DES interactions, the formation mechanism of the system was studied in terms of H-bond density and radial distribution function (RDF) using molecular dynamics modeling. Furthermore, density functional theory (DFT) was used to evaluate the topological characteristics of the polymeric system such as potential energy density (PED), laplacian electron density (LED), energy density, and kinetic energy density (KED) at bond critical points (BCPs) between the cellulose and the DES. The quantum theory of atoms in molecules (AIM), Bader's quantum theory (BQT), and reduced density gradient (RDG) scatter plots have been exploited to estimate and locate non-covalent interactions (NCIs). The results revealed that the dissolution process is attributed to the physical interactions, mainly the strong H-bond interactions.

Dual stimuli-responsive phosphorescence of a Pb(II) coordination polymer to acidic vapors and thermal treatment

We present a new intensely phosphorescent Pb(II) coordination polymer (1) containing a heteroatomic ligand. It has a quantum yield of 21.62% and a lifetime of 25.46 μs. The naked-eye solid-state photoluminescence of 1 significantly changes in response to acidic vapors and thermal treatment, indicating the coexistence of acidochromic and thermochromic luminescence.

Crystal structure and Hirshfeld surface analysis of (3aR,4S,7S,7aS)-4,5,6,7,8,8-hexa-chloro-2-{6-[(3aR,4R,7R,7aS)-4,5,6,7,8,8-hexa-chloro-1,3-dioxo-1,3,3a,4,7,7a-hexa-hydro-2H-4,7-methano-isoindol-2-yl]hex-yl}-3a,4,7,7a-tetra-hydro-1H-4,7-methano-iso-indole-1,3(2H)-dione

The mol-ecule of the title compound, C24H16Cl12N2O4, is generated by a crystallographic inversion centre at the midpoint of the central C-C bond. A kink in the mol-ecule is defined by a torsion angle of -169.86 (15)° about this central bond of the alkyl bridge. The pyrrolidine ring is essentially planar [max. deviation = 0.014 (1) Å]. The cyclo-hexane ring has a boat conformation, while both cyclo-pentane rings adopt an envelope conformation. In the crystal structure, mol-ecules are linked by inter-molecular C-H⋯O, C-H⋯Cl and C-Cl⋯π inter-actions, and short inter-molecular Cl⋯O and Cl⋯Cl contacts, forming a three-dimensional network.

Crystal structure and Hirshfeld surface analysis of 1,3-bis-{2,2-di-chloro-1-[(E)-phenyl-diazen-yl]ethen-yl}benzene

In the mol-ecule of the title compound, C22H14Cl4N4, the central benzene ring makes dihedral angles of 77.03 (9) and 81.42 (9)° with the two approximately planar 2,2-di-chloro-1-[(E)-phenyl-diazen-yl]vinyl groups. In the crystal, mol-ecules are linked by C-H⋯π, C-Cl⋯π, Cl⋯Cl and Cl⋯H inter-actions, forming a three-dimensional network. The Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (30.4%), C⋯H/H⋯C (20.4%), Cl⋯H/H⋯Cl (19.4%), Cl⋯Cl (7.8%) and Cl⋯C/C⋯Cl (7.3%) inter-actions.

Crystal structure and Hirshfeld surface analysis of dimethyl 5-[2-(2,4,6-trioxo-1,3-diazinan-5-yl-idene)hydrazin-1-yl]benzene-1,3-di-carboxyl-ate 0.224-hydrate

In the crystal, the whole mol-ecule of the title compound, C14H12N4O7·0.224H2O, is nearly planar with a maximum deviation from the least-squares plane of 0.352 (1) Å. The mol-ecular conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond, generating an S(6) ring motif. In the crystal, mol-ecules are linked by centrosymmetric pairs of N-H⋯O hydrogen bonds, forming ribbons along the c-axis direction. These ribbons connected by van der Waals contacts, forming sheets parallel to the ac plane. There are also inter-molecular van der Waals contacts and and C-H⋯π inter-actions between the sheets. A Hirshfeld surface analysis indicates that the most prevalent inter-actions are O⋯H/H⋯O (41.2%), H⋯H (19.2%), C⋯H/H⋯C (12.2%) and C⋯O/ O⋯C (8.4%).

Modified-amino acid/peptide pyrimidine analogs: synthesis, structural characterization and DFT studies of N-(pyrimidyl)gabapentine and N-(pyrimidyl)baclofen

H-Bonding networks and π–π and halogen bonding interactions in the crystal structures of N-modified amino acid pyrimidine analogs are investigated using DFT calculations and X-ray crystallography analysis.

Pre-organisation of ligand donor sets modulates the supramolecular structure of bis(pyridyl–imine) silver(i) chelates

Ligands comprising o-, m- or p-phenylenediamine coupled to pyridine-2-carbaldehyde were coordinated to silver(i). By controlling the positions of the ligand donor sets, the supramolecular structure of the coordination compounds was manipulated.

Crystal engineering strategies towards halogen-bonded metal–organic multi-component solids: salts, cocrystals and salt cocrystals

This highlight presents an overview of the current advances in the preparation of halogen bonded metal–organic multi-component solids, including salts and cocrystals comprising neutral and ionic constituents.

(E)-1-(2,6-Di-chloro-phen-yl)-2-(3-nitro-benzyl-idene)hydrazine: crystal structure and Hirshfeld surface analysis

The stabilized conformation of the title compound, C13H9Cl2N3O2, is similar to that of the isomeric compound (E)-1-(2,6-di-chloro-phen-yl)-2-(2-nitro-benzyl-idene)hydrazine. The 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 26.25 (16)°. In the crystal, face-to-face π-π stacking inter-actions along the a-axis direction occur between the centroids of the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring. The mol-ecules are further linked by C-H⋯O contacts and N-H⋯O and C-H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded mol-ecular layers parallel to (100). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (22.1%), Cl⋯H/H⋯Cl (20.5%), O⋯H/H⋯O (19.7%), C⋯C (11.1%) and C⋯H/H⋯C (8.3%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-1-(2,6-di-chloro-phen-yl)-2-(2-nitro-benzyl-idene)hydrazine

In the title compound, C13H9Cl2N3O2, the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 21.16 (14)°. In the crystal, face-to-face π-π stacking inter-actions occur along the a-axis direction between the centroids of the 2,6-di-chloro-phenyl ring and the nitro-substituted benzene ring. Furthermore, these mol-ecules show intra-molecular N-H⋯Cl and C-H⋯O contacts and are linked by inter-molecular N-H⋯O and C-H⋯Cl hydrogen bonds, forming pairs of hydrogen-bonded mol-ecular layers parallel to (20). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (23.0%), O⋯H/H⋯O (20.1%), Cl⋯H/H⋯Cl (19.0%), C⋯C (11.2%) and H⋯C/C⋯H (8.0%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-4-{2,2-di-chloro-1-[(3,5-di-methyl-phen-yl)diazen-yl]ethen-yl}-N,N-di-methyl-aniline

In the title compound, C18H19Cl2N3, the planes of the benzene rings subtend a dihedral angle of 77.07 (10)°. In the crystal, mol-ecules are associated into inversion dimers via short Cl⋯Cl contacts [3.3763 (9) Å]. A Hirshfeld surface analysis indicates that the most important contact percentages for the different types of inter-actions are H⋯H (43.9%), Cl⋯H/H⋯Cl (22.9%), C⋯H/H⋯C (20.8%) and N⋯H/H⋯N (8.0%).

Crystal structure and Hirshfeld surface analysis of 4-{2,2-di-chloro-1-[(E)-(4-fluoro-phen-yl)diazen-yl]ethen-yl}-N,N-di-methyl-aniline

In the title compound, C16H14Cl2FN3, the dihedral angle between the two aromatic rings is 64.12 (14)°. The crystal structure is stabilized by a short Cl⋯H contact, C-Cl⋯π and van der Waals inter-actions. The Hirshfeld surface analysis and two-dimensional fingerprint plots show that H⋯H (33.3%), Cl⋯H/H⋯Cl (22.9%) and C⋯H/H⋯C (15.5%) inter-actions are the most important contributors towards the crystal packing.

Crystal structure and Hirshfeld surface analysis of (E)-3-(benzyl-idene-amino)-5-phenyl-thia-zolidin-2-iminium bromide

The central thia-zolidine ring of the title salt, C16H16N3S+·Br-, adopts an envelope conformation, with the C atom bearing the phenyl ring as the flap atom. In the crystal, the cations and anions are linked by N-H⋯Br hydrogen bonds, forming chains parallel to the b-axis direction. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (46.4%), C⋯H/H⋯C (18.6%) and H⋯Br/Br⋯H (17.5%) inter-actions.

The (Dioximate)NiII/I2 System: Ligand Oxidation and Binding Modes of Triiodide Species

Reinvestigation of (o-benzoquinonedioximate)₂Ni/I₂ systems demonstrated that the reaction itself and also the crystallization conditions dramatically affect the identity of generated species. Crystallization (CHCl₃, 20-25 °C) of the nickel(II) dioximate complex [Ni(bqoxH)₂] (bqoxH₂ = o-benzoquinonedioxime) with I₂ in the 1:(1-10) molar ratios of the reactants led to several (o-benzoquinonedioximate)₂Ni derivatives and/or iodine adducts [Ni(I)(bqoxH)(bqoxH₂)]·³/₂I₂, [Ni(I₃)(bqoxH)(bqoxH₂)]·[Ni(bqoxH)₂], and [Ni(I₃)(bqox^•-)(bqoxH₂)]·I₂; the latter one, featuring the anion-radical bqox^•- ligand, is derived from the formal (-2H⁺/1e^-)-oxidation of bqoxH₂. In these three adducts, various types of noncovalent interactions were identified experimentally and their existence was supported theoretically. The [Ni(I₃)(bqox^•-)(bqoxH₂)]·I₂ adduct exhibits simultaneous semicoordination and coordination patterns of the triiodide ligand; this is the first recognition of the semicoordination of any polyiodide ligand to a metal center. The semicoordination noncovalent contact Ni···I₃ (3.7011(10) Å) is substantially longer that the Ni-I₃ coordination bond (2.8476(9) Å), and the difference in energies between these two types of linkages is 8-12 kcal/mol.

Crystal structures of N6-modified-amino acid nucleobase analogs(iii): adenine–valeric acid, adenine–hexanoic acid and adenine–gabapentine

H-bonding networks, anion–π and π–π interactions in the crystal structures of N⁶-modified-amino acid adenine analogs are investigated by means of DFT calculations and X-ray crystallography analysis.

Supramolecular assemblies involving salt bridges: DFT and X-ray evidence of bipolarity

Three new aminopyridinium/4,4′-oxydibenzoate salts have been synthesized and structurally characterized. A common feature of these compounds is the formation of antiparallel π-stacked salt bridges.

Crystal structure and Hirshfeld surface analysis of 5-(3,5-di-tert-butyl-4-hy-droxy-phen-yl)-3-phenyl-4,5-di-hydro-1H-pyrazole-1-carboxamide

In the title compound, C24H31N3O2, the mean plane of the central pyrazole ring [r.m.s. deviation = 0.095 Å] makes dihedral angles of 11.93 (9) and 84.53 (8)°, respectively, with the phenyl and benzene rings. There is a short intra-molecular N-H⋯N contact, which generates an S(5) ring motif. In the crystal, pairs of N-H⋯O hydrogen bonds link inversion-related mol-ecules into dimers, generating an R 2 2(8) ring motif. The Hirshfeld surface analysis indicates that the most significant contribution involves H⋯H contacts of 68.6.

Crystal structure and Hirshfeld surface analysis of (E)-4-{[2,2-di-chloro-1-(4-meth-oxy-phen-yl)ethen-yl]diazen-yl}benzo-nitrile

In the title compound, C16H11Cl2N3O, the 4-meth-oxy-substituted benzene ring makes a dihedral angle of 41.86 (9)° with the benzene ring of the benzo-nitrile group. In the crystal, mol-ecules are linked into layers parallel to (020) by C-H⋯O contacts and face-to-face π-π stacking inter-actions [centroid-centroid distances = 3.9116 (14) and 3.9118 (14) Å] between symmetry-related aromatic rings along the a-axis direction. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from Cl⋯H/H⋯Cl (22.8%), H⋯H (21.4%), N⋯H/H⋯N (16.1%), C⋯H/H⋯C (14.7%) and C⋯C (9.1%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-3-[(4-chloro-benzyl-idene)amino]-5-phenyl-thia-zolidin-2-iminium bromide

The title salt, C16H15ClN3S+·Br-, is isotypic with (E)-3-[(4-fluoro-benzyl-idene)amino]-5-phenyl-thia-zolidin-2-iminium bromide [Khalilov et al. (2019 ▸). Acta Cryst. E75, 662-666]. In the cation of the title salt, the atoms of the phenyl ring attached to the central thia-zolidine ring and the atom joining the thia-zolidine ring to the benzene ring are disordered over two sets of sites with occupancies of 0.570 (3) and 0.430 (3). The major and minor components of the disordered thia-zolidine ring adopt slightly distorted envelope conformations, with the C atom bearing the phenyl ring as the flap atom. In the crystal, centrosymmetrically related cations and anions are linked into dimeric units via N-H⋯Br hydrogen bonds, which are further connected by weak C-H⋯Br contacts into chains parallel to the a axis. Furthermore, not existing in the earlier report of (E)-3-[(4-fluoro-benzyl-idene)amino]-5-phenyl-thia-zolidin-2-iminium bromide, C-H⋯π inter-actions and π-π stacking inter-actions [centroid-to-centroid distance = 3.897 (2) Å] between the major components of the disordered phenyl ring contribute to the stabilization of the mol-ecular packing. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions for the crystal packing are from H⋯H (30.5%), Br⋯H/H⋯Br (21.2%), C⋯H/H⋯C (19.2%), Cl⋯H/H⋯Cl (13.0%) and S⋯H/H⋯S (5.0%) inter-actions.

Nitropyridine-1-Oxides as Excellent π-Hole Donors: Interplay between σ-Hole (Halogen, Hydrogen, Triel, and Coordination Bonds) and π-Hole Interactions

In this manuscript, we use the primary source of geometrical information, i.e., Cambridge Structural Database (CSD), combined with density functional theory (DFT) calculations (PBE0-D3/def2-TZVP level of theory) to demonstrate the relevance of π-hole interactions in para-nitro substituted pyridine-1-oxides. More importantly, we show that the molecular electrostatic potential (MEP) value above and below the π–hole of the nitro group is largely influenced by the participation of the N-oxide group in several interactions like hydrogen-bonding (HB) halogen-bonding (XB), triel bonding (TrB), and finally, coordination-bonding (CB) (N⁺–O⁻ coordinated to a transition metal). The CSD search discloses that p-nitro-pyridine-1-oxide derivatives have a strong propensity to participate in π-hole interactions via the nitro group and, concurrently, N-oxide group participates in a series of interactions as electron donor. Remarkably, the DFT calculations show from strong to moderate cooperativity effects between π–hole and HB/XB/TrB/CB interactions (σ-bonding). The synergistic effects between π-hole and σ-hole bonding interactions are studied in terms of cooperativity energies, using MEP surface analysis and the Bader’s quantum theory of atoms in molecules (QTAIM).

Crystal structure and Hirshfeld surface analysis of (E)-3-[(4-fluoro-benzyl-idene)amino]-5-phenyl-thia-zolidin-2-iminium bromide

In the cation of the title salt, C16H15FN3S+·Br-, the phenyl ring is disordered over two sets of sites with a refined occupancy ratio of 0.503 (4):0.497 (4). The mean plane of the thia-zolidine ring makes dihedral angles of 13.51 (14), 48.6 (3) and 76.5 (3)° with the fluoro-phenyl ring and the major- and minor-disorder components of the phenyl ring, respectively. The central thia-zolidine ring adopts an envelope conformation. In the crystal, centrosymmetrically related cations and anions are linked into dimeric units via N-H⋯Br hydrogen bonds, which are further connected by weak C-H⋯Br hydrogen bonds into chains parallel to [110]. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (44.3%), Br⋯H/H⋯Br (16.8%), C⋯H/H⋯C (13.9%), F⋯H/H⋯F (10.3%) and S⋯H/H⋯S (3.8%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-1-[2,2-di-chloro-1-(4-nitro-phen-yl)ethen-yl]-2-(4-fluoro-phen-yl)diazene

In the title compound, C14H8Cl2FN3O2, the 4-fluoro-phenyl ring and the nitro-substituted benzene ring form a dihedral angle of 63.29 (8)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into chains running parallel to the c axis. The crystal packing is further stabilized by C-Cl⋯π, C-F⋯π and N-O⋯π inter-actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯O/O⋯H (15.5%), H⋯H (15.3%), Cl⋯H/H⋯Cl (13.8%), C⋯H/H⋯C (9.5%) and F⋯H/H⋯F (8.2%) inter-actions.

Diverse structural assemblies of U-shaped hydrazinyl-sulfonamides: experimental and theoretical analysis of non-covalent interactions stabilizing solid state conformations

The preparation and structures of five new U-shaped hydrazinyl-sulfonamides are reported.

Experimental and theoretical study of Pb⋯S and Pb⋯O σ-hole interactions in the crystal structures of Pb(ii) complexes

The crystal structures of two novel Pb(ii) hemidirected compounds present considerably strong Pb⋯S σ-hole bonding as the main intermolecular interactions.

Crystal structures of N6-modified-amino acid related nucleobase analogs (II): hybrid adenine-β-alanine and adenine-GABA molecules

H-Bonding networks and anion–π interactions in the crystal structures of N⁶-modified-amino acid adenine analogs are investigated using X-ray crystallography and DFT calculations.

Unexpected chalcogen bonds in tetravalent sulfur compounds

Combined CSD analysis and theoretical calculations show the importance of the polarizability in chalcogen bonding interactions. We provide evidence that the Lewis base has a preference in some cases for the σ-hole that is opposite to the more polarizable group instead of the more electron withdrawing one.

Crystal structure of (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl) terephthalic acid-dimethylsulfoxide (1/1), C18H15N3O6 ⋅ C2H6OS

C18H15N3O6 ⋅ C2H6OS, P21/c (no. 14), a = 15.762(9) Å, v = 6.013(4) Å, c = 22.264(11) Å, β = 103.522(19)°, V = 2052(2) Å3, Z = 4, Rgt(F) = 0.0484, wRref(F2) = 0.1348, T = 296(2) K.

Synthesis of Metallomacrocycle and Coordination Polymers with Pyridine-Based Amidocarboxylate Ligands and Their Catalytic Activities towards the Henry and Knoevenagel Reactions

The reactions of 3,3'-{(pyridine-2,6-dicarbonyl)bis(azanediyl)}dibenzoic acid (H2L) with zinc(II), cadmium(II), and samarium(III) nitrates were studied, and the obtained compounds, [Zn(1κO:2κO'-L)(H2O)2] n (1), [Cd(1κO 2:2κO 2-L)(H2O)2]2 ⋅6n H2O⋅ n C4H8O2 ⋅1.5n DMF (2), and [Sm(1κO:2κO'O'':3κO'''-L)(NO3)(H2O)(dmf)] n ⋅ n DMF (3), were characterized by elemental analysis, FTIR spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction. Compounds 1 and 3 have 1D zigzag- and double-chain-type structures, respectively, whereas 2 features a dinuclear metallomacrocyclic complex. The ligand (L2-) orients in different conformations, that is, syn-syn for 1 and anti-anti for 2 and 3. Compound 1 is the first example in which the syn-syn conformation for this ligand has been observed. These compounds act as heterogeneous catalysts for the nitroaldol (Henry; in water medium) and Knoevenagel condensation reactions of different aldehydes, and the most effective is zinc coordination polymer 1. Recyclability, heterogeneity, and size-selectivity tests were performed, which showed that the catalyst was highly active over at least four recycling runs.

Intermolecular hydrogen bonding H···Cl in crystal structure of palladium(II)-bis(diaminocarbene) complex

The reaction of bis(isocyanide)palladium complex cis-[PdCl2(CNXyl)2] (Xyl=2,6-Me2C6H3) with excess of 4,5-dichlorobenzene-1,2-amine in a C2H4Cl2/MeOH mixture affords monocationic bis(diaminocarbene) complex cis-[PdClC{(NHXyl)=NHC6H2Cl2 NH2}{C(NHXyl)=NHC6H2Cl2NH2}]Cl (3) in moderate yield (42%). Complex 3 exists in the solid phase in the H-bonded dimeric associate of two single charged organometallic cations and two chloride anions according to X-ray diffraction data. The Hirshfeld surface analysis for the X-ray structure of 3 reveals that the crystal packing is determined primarily by intermolecular contacts H–Cl, H–H, and H–C. The intermolecular hydrogen bonds N–H···Cl and C–H···Cl in the H-bonded dimeric associate of 3 were studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method, and estimated energies of these supramolecular contacts vary from 1.6 to 9.1 kcal/mol. Such non-covalent bonding means that complex 3 is an anionic receptor for the chloride anions.