Thermal Behaviour of the N-donor Adducts of Metal Saccharinates III. Imidazole saccharinates of Co(II), Ni(II) and Cd(II)

The complexes [M(HIm)₄(H₂O)₂](sac)₂ (M=Co, Ni) and [Cd(HIm)₂(sac)₂]₂ with saccharin (sac) and imidazole (HIm) were synthesized and their thermal (TG, DTG and DTA) behaviour in the interval from room temperature up to 1000°C in a static air atmosphere was investigated. Irrespectively of whether the deprotonated saccharinato residues are present as ligands or ions or both as ligands and ions, the anhydrous complexes regularly decompose in two stages. The thermal data of 16 saccharinato complexes (including the title compounds) were correlated with the respective structural data. The general thermal stability order of the saccharinato complexes can be represented as: Pb(II)<Zn(II)<Co(II)Ni(II)<Cd(II) (the stability of the Cu saccharinates depends on the particular compound) and is dictated by several structural factors, e.g. metal ionic radii, participation of the water in the coordination sphere of the metal and other structural characteristics. This revised version was published online in August 2006 with corrections to the Cover Date.     

ON THE COORDINATION IN METAL SACCHARINATES. IMPLICATIONS FOR BOND-ORDER MODELS OF METAL – LIGAND BINDING

Abstract

The structures of saccharinates retrieved from the Cambridge Structural Database were used to discuss the coordination propcrties of deprotonated saccharin. The series of the first-row metal(II) saccharinato isomorphs and of tnphenylstannyl sacchainates were analyzed within the bond valence model (BVM). The “relative radius” parameter of the saccharinato ligand for the M(Ow)₄(Nsac)₂ type of coordination was estimated (1.424 Å) from correlation of the metal-N(saccharinato) distances with the Shannon-Prewitt ionic radii.

Making use of the exponential bond distance-bond order (BDBO) relation of Pauling within the BVM, ligand-specific mean bond order sums (MBOS) were recently derived for several ligands. Coupled with the coordination number (CN), they are predictive for the metal-ligand bond lengths. Using parameterized power function instead of the exponential form of the BDBO relation, a new set of MBOS's is derived here: isothiocyanate 2.56 ± 0.06; pyridine 1.84 ± 0.16; imidazole 2.02 ± 0.12; chloride 2.05 ± 0.10; water 1.54 ± 0.03. The two sets of MBOS values can be used to predict the metal-ligand distances nearly equally well, showing that the distances are solely predetermined by the MBOS and CN values, independently of the particular form of BDBO relation used.     

Vibrational study and spectra-structure correlations in ammonium saccharinate: comparison with the alkali saccharinates

The FT IR spectra, at temperatures from liquid-nitrogen boiling (LNT) up to room temperature (RT), as well as the RT Raman solid-state spectra of protonated and deuterated ammonium saccharinate and of a series of alkali (Na, K, Rb, Cs) saccharinates are studied. The spectral assignments are aided with ab initio calculations on the free saccharinato anion at the HF/6-31 + + G(d,p) level. Attention is paid to the ND, CO and SO2 stretching regions. Correlation splitting is believed to be responsible for the presence of a v(CO) doublet. The averaged v(CO) frequency in (purely ionic) ammonium saccharinate is found to be the lowest in the so far studied saccharinates, along with the assumptions that the v(CO) frequency (or the corresponding averaged value) can have predictive value for the type of the metal-to-saccharinato ligand/ion bonding. The appreciably higher contribution of the dominating internal coordinate in the corresponding normal vibration in case of v(as)(SO2) than in v(s)(SO2) makes it suitable for spectra-structure correlations. Contrary to RT, even though no phase transitions were observed in the studied temperature range, some polycentered character is prescribed to the hydrogen bonds in which the ammonium ions of effective symmetry C8 participate at LNT. Certain structural predictions about the saccharinates of K, Rb and Cs are made.     

Synthesis and spectroscopic studies of novel Cu(II), Co(II), Ni(II) and Zn(II) mixed ligand complexes with saccharin and nicotinamide

Four novel mixed ligand complexes of Cu(II), Co(II), Ni(II) and Zn(II) with saccharin and nicotinamide were synthesised and characterised on the basis of elemental analysis, FT-IR spectroscopic study, UV–Vis spectrometric and magnetic susceptibility data. The structure of the Cu (II) complex is completely different from those of the Co(II), Ni(II) and Zn(II) complexes. From the frequencies of the saccharinato CO and SO₂ modes, it has been proven that the saccharinato ligands in the structure of the Cu complex are coordinated to the metal ion ([Cu(NA)₂(Sac)₂(H₂O)], where NA — nicotinamide, Sac — saccharinato ligand or ion), whilst in the Co(II), Ni(II) and Zn(II) complexes are uncoordinated and exist as ions ([M(NA)₂(H₂O)₄](Sac)₂).     

N‐Methyl‐N‐(1‐phenyl­sulfonyl­indol‐2‐ylmethyl)­aniline

In the title compound, 2‐[(methylphenylamino)methyl]‐1‐(phenylsulfonyl)indole, C₂₂H₂₀N₂O₂S, the indole system is not strictly planar and the dihedral angle between the fused rings is 2.7 (1)°. The angles around the S atom of the sulfonyl substituent deviate significantly from the ideal value for tetrahedral geometry. The pyramidalization at the indole N atom is very small. Of the two C—H?O interactions, one influences the orientation of indole with respect to the sulfonyl group and the other determines the orientation of the phenyl bound to sulfonyl. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 89.6 (1)° with the best plane of the indole. The molecular packing is stabilized by C—H?π and C—H?O hydrogen bonds.     

Tetraaquabis(pyridine)metal(II) saccharinate tetrahydrate, [M(H2O)4(py)2](sac)2·4H2O; M = Co,Ni. Crystal structure determination

The crystal structure determination of the title compounds showed that they are isomorphous, revealing the general formula [M(H₂O)₄(py)₂](sac)₂·4H₂O. Their structures are built up of [M(H₂O)₄(py)₂]²⁺ cations, saccharinato anions and non-coordinated water molecules. The metal atom lies on the inversion center and is octahedrally coordinated by four water oxygens and two pyridine nitrogen atoms. The crystal structure packing is achieved through the hydrogen bonds of O_w⋯O_w, O_w⋯O and O_w⋯N type. Coordinated water molecules are hydrogen bonded to non-coordinated ones at the same time participating in hydrogen bonding with carbonyl oxygen and nitrogen atom from the saccharinato anions. Non-coordinated water molecules participate in hydrogen bonding with the oxygen atoms belonging to the saccharinato CO and SO₂ groups. The hydrogen bond network between the oxygen atoms belonging to the SO₂ group of the saccharinato anions and one of the non-coordinated water molecules (OW3) constructs the centrosymmetric cavity in the structure.     

The molecular and crystal structure of stable 5-methyl-2-methylsulfonyl-3-thiophenecarbonitrile oxide

A stable thiophene derivative, 5-methyi-2-methylsulfonyl-3-thiophenecarbonitrile oxide, which is active in reactions with dipolarophiles, was studied by means of X-ray structural analysis. In the crystalline state the structure includes two independent molecules with similar values of geometric and conformation parameters. The bond angle at the C atom of the nitrile oxide group is significantly different from 180°. The intramolecular distances between the C and S atoms in the nitrile oxide and sulfonyl groups are well below the equilibrium distance. The stability of the molecule is thought to be increased by electrostatic or donor-acceptor interactions between the atoms of these groups. The mutual orientation of the two independent molecules in the crystal is nearly orthogonal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–727, April, 1993.     

Electronic structure of the sulfonyl and phosphonyl groups: a computational and crystallographic study

A computational and X-ray crystallographic investigation of the electronic and geometric structures of a range of sulfonyl (-SO(2)-) and phosphonyl (-PO(2)--) containing species was undertaken to investigate the nature of valency and bonding in these functional groups. The traditional representation of sulfonyl and phosphonyl species is with octet-violating Lewis structures, which require d-orbital participation at the central atom. However, computational studies cast serious doubt upon this bonding model. In this work, we have employed NBO/NRT analysis to investigate hybridization, atomic formal charges, donor-acceptor interactions, and resonance structure contributions. Our results predict that within sulfonyl and phosphonyl systems, bonding interactions are highly polarized, of the form X+-Y- (X = P, S), and possess additional contributions from reciprocal n --> sigma* interactions where substituents off sulfur or phosphorus simultaneously act as donors and acceptors. Experimental evidence for the proposed bonding arrangement is provided for the sulfonyl functional group through a series of low-temperature X-ray structure correlations for sulfate monoesters, sulfamates, and methanesulfonates. Examination of changes to bond lengths and geometries upon substituent variation support the computational results. Together, our studies lend support for a bonding network in sulfonyl and phosphonyl groups composed of polar interactions augmented with reciprocal hyperconjugative bonding, which does not necessitate significant d-orbital participation nor formal octet violation at the central sulfur or phosphorus.     

An experimental and theoretical study of the structure of Lamotrigine in its neutral and protonated forms: evidence of Lamotrigine enantiomers

The energies, geometries, and NMR chemical shifts have been calculated at the B3LYP/6-311++G(d,p) level for 17 structures of the anticonvulsant drug Lamotrigine and 29 structures of protonated Lamotrigine, including tautomers and E/Z isomers of the imino groups. The calculations were compared with solid state (X-ray and CPMAS NMR) and solution experimental results both reported in the literature and determined in this work. The conclusion is that Lamotrigine exists as the diamino tautomer and that its protonation takes place on the N2 atom. Using ABTE and/or deuterated ABTE as chiral solvating agent, it has been demonstrated for the first time by NMR in solution that Lamotrigine is a racemate of rapidly interconverting enantiomers. The crystal structure of two new solvated salts of Lamotrigine, both saccharinates, has been determined. Both salts present the same arrangement in chains of Lamotrigine and saccharinate joined by hydrogen bonds and stacking interactions. No isostructurality is present because of the different arrangement of the chains in both crystal structures.     

True symmetry or pseudosymmetry: 5‐amino‐1‐(4‐methylphenylsulfonyl)‐4‐pyrazolin‐3‐one and a comparison with its 1‐phenylsulfonyl analogue

The title compound, C₁₀H₁₁N₃O₃S, (I), crystallizes as the NH tautomer. The two rings subtend an interplanar angle of 72.54 (4)°. An intramolecular hydrogen bond is formed from the NH₂ group to a sulfonyl O atom. The molecular packing involves layers of molecules parallel to the bc plane at x≃ 0, 1 etc., with two classical linear hydrogen bonds (amino–sulfonyl and pyrazoline–carbonyl N—H...O) and a further interaction (amino–sulfonyl N—H...O) completing a three‐centre system with the intramolecular contact. The analogous phenyl derivative, (II) [Elgemeie, Hanfy, Hopf & Jones (1998). Acta Cryst. C 54 , 136–138], crystallizes with essentially the same unit cell and packing pattern, but with two independent molecules that differ significantly in the orientation of the phenyl groups. The space group is P2₁/c for (I) but P2₁ for (II), which is thus a pseudosymmetric counterpart of (I).     

Bis­(saccharinato‐κN)zinc(II) com­plexes with N,N′‐bidentate 2‐amino­methyl­pyridine and 2‐amino­ethylpyridine

The structures of trans‐bis[2‐(amino­methyl)­pyridine‐κ²N,N′]­bis­(saccharinato‐κN)­zinc(II), [Zn(C₇H₄NO₃S)₂(C₆H₈N₂)₂], (I), and [2‐(amino­ethyl)­pyridine‐κ²N,N′]bis­(saccharinato‐κN)­zinc(II), [Zn(C₇H₄NO₃S)₂(C₇H₁₀N₂)], (II), exhibit octa‐ and tetrahedrally coordinated Zn^II atoms, respectively. The di­amine ligands behave as N,N′‐bidentate ligands, while saccharinate (sac) is coordinated through the N atom. In (I), the complex lies about an inversion centre with the Zn atom disordered and displaced by 0.256 (2) Å from a centre of symmetry towards a sac N atom. The crystal structure of (I) is stabilized by N—H⋯O hydrogen bonds and the crystal packing of (II) is determined by hydrogen bonding as well as weak π–π stacking interactions between the sac ligands.     

Angular correlation of electrons in the ground state of helium

The spatial angular correlation of electrons in the ground state of the helium atom has been examined using configuration interaction and Hylleraas wave-functions. It was found that, in general, the average angle between the electrons is not a maximum when the two electrons are at the same distance from the nucleus. For configuration interaction wave-functions there is a position of the electrons for which the average value of the angle between the electrons is a maximum. Hylleraas wave-functions do not show this behavior.     

N‐{4‐Bromo‐2‐[(3‐bromo‐1‐phenylsulfonyl‐1H‐indol‐2‐yl)methyl]‐5‐methoxyphenyl}acetamide

In the title compound, C₂₄H₂₀Br₂N₂O₄S, the indole ring system is planar and the S atom has a distorted tetrahedral configuration. The sulfonyl‐bound phenyl ring is orthogonal to the indole ring system and the conformation of the phenyl­sulfonyl substituent with respect to the indole moiety is influenced by intramolecular C—H⃛O hydrogen bonds involving the two sulfonyl O atoms. The mean plane through the acetyl­amido group makes a dihedral angle of 57.0 (1)° with the phenyl ring of the benzyl moiety. In the crystal, glide‐related mol­ecules are linked together by N—H⃛O hydrogen bonds and C—H⃛π interactions to form molecular chains, which extend through the crystal. Inversion‐related chains are interlinked by C—H⃛π interactions to form molecular layers parallel to the bc plane. These layers are interconnected through π–π interactions involving the five‐ and six‐membered rings of the indole moiety.     

Pnictogen-Bridged Diphenyl Sulfones as Photoinduced Pnictogen Bond Forming Emission Motifs

In this study, pnictogen (Pn)-bridged diphenyl sulfones were synthesized as motifs for photoinduced dynamic rearrangement. The newly synthesized sulfones exhibited dual fluorescence at 298 K. Density functional theory calculations revealed that the longer-wavelength fluorescence was derived from the geometries after structural relaxation through photo-driven pnictogen bond formation between the O atom lone pair of the sulfonyl moiety and the antibonding orbital of the Pn−C bond. This is the first report on emission dynamics driven by pnictogen bond formation upon photoexcitation.     

cis-bis(Saccharinato)cobalt(II) and -zinc(II) complexes with 2-dimethylaminoethanol: syntheses,crystal structures,spectroscopic and thermal studies

2-Dimethylaminoethanol (dmea) reacted with tetraaqua-bis(saccharinato)cobalt(II) and -zinc(II) in n-butanol to yield the new complexes cis-[Co(sac)₂(dmea)₂] (1), and cis-[Zn(sac)₂(dmea)₂] (2) (sac?=?saccharinate). The complexes were characterized by elemental analyses, IR spectroscopy, DTA-TG and X-ray crystallography. Both complexes are isomorphous and crystallize in the monoclinic space group P2₁/c. The cobalt(II) and zinc(II) ions are coordinated by two neutral dmea ligands and two sac anions in a distorted octahedral environment. The dmea ligand acts as a bidentate N, O donor through the amine N and hydroxyl O atoms, while the sac ligand exhibits non-equivalent coordination, behaving as an ambidentate ligand; one coordinates to the metal via the carbonyl oxygen atom, while the other is N-bonded. The packing of the molecules in the crystals of both complexes is achieved by aromatic π(sac)–π(sac) stacking interactions, C–H?·?π interactions and weak intermolecular C–H?·?O hydrogen bonds involving the methyl groups of dmea and the sulfonyl oxygen atoms of the sac ligands. IR and UV spectra and thermal analysis are in agreement with the crystal structures.     

聚丙烯腈PAN分子链的第一性原理研究

The equilibrium geometries of the polyacrylonitrile (PAN) chain was theoretically studied using the Hartree-Fock method at the STO-3G levels. As for the optimized structures, the average distance of the C atom couple in the main chain is 155.6 pm; the average distance of the C atom couple in the branch chain is 149.7 pm; the average distance between a C atom bonding with N atom is 115.5 pm. For the charge distribution, because of the influence of a N atom with its comparatively larger negative charge, the C atoms in the main chain are different in their charge distribution. Finally, the vibration models of the chain have been analyzed to clarify the reaction sequence of dehydrogenation and cyclization during pre oxidation and carbonization of the polyacrylonitrile.     

Metal Complexes of Saccharin with the N-(2-hydroxyethyl)-ethylenediamine Ligand: Synthesis,Characterization and Spectroscopic Examination. Crystal Structures of trans- Bis(Saccharinato)Bis{N-(2-hydroxyethyl)-Ethylenediamine} copper(II) and Cadmium(II)

The novel transition metal saccharinato complexes of N-(2-hydroxyethyl)-ethylendiamine (HydEt-en) have been synthesized and characterized by elemental analyses, magnetic moments, UV-Vis and IR spectra. Coordination behaviour of HydEt-en has been studied. The Mn(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) form mononuclear complexes, while the Fe(II) and Co(II) complexes are dimeric. The crystal structures of the [Cu(sac)₂(HydEt-en)₂] and [Cd(sac)₂(HydEt-en)₂] complexes, where sac is the deprotonated form of saccharin, were determined by x-ray diffraction. The metal ions are octahedrally coordinated by these ligands. The amine ligand acts as a bidentate N-donor ligand and its ethanol group is not involved in coordination. The sac ions coordinate through the deprotonated N as a monodentate ligand. The NH and OH groups of the amine ligand are involved in intra- and intermolecular hydrogen bonding with the carbonyl and sulphonyl oxygens of the sac ions to form a three-dimensional infinite network.     

DFT study of electronic structure of saccharin,thiosaccharin, and their respective ions: Effects of metal coordination on thiosaccharinate electronic structure

A rationalization of the conspicuous different abilities of saccharin and thiosaccharin to form coordination compounds with the first series of transition metal elements and to interact with heavy metal cations is sought. Their electronic molecular structures as well as those of their respective ions are compared performing natural bond orbitals (NBO) analyses of the four species. Upon deprotonation, the negative charge at the N atom in saccharin is almost constant while it decreases in thiosaccharin and the negative charge at the monocoordinated chalcogen atom is notably more increased in the latter than in the former. Apparently, the negative charge reorganization makes difficult the coordination of thiosaccharin with the first series of transition metal elements and favors its experimentally observed interaction with heavy metal cations such as cadmium, lead, mercury, silver, and thallium. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Ligand close packing and the geometries of A(XY)4 and some related molecules

Molecules of the type A(OX)₄, A(NX₂)₄ and A(CY₂X)₄ are not regularly tetrahedral about the central atom A. Two of the angles about this central atom are smaller than tetrahedral and four are larger, or four are smaller and two larger. By considering that the ligand atom (O, N or C) that is bonded to the central atom A has three intramolecular ligand radii and minimising the number of ligand–ligand contact distances, as described in the theory of ligand close packing, we are able to account for the S₄ and D_2d geometries observed for C(OCH₃)₄, C(OPh)₄ and CEE₄ and related molecules. The ligand close packing model also rationalises the C₂ geometries of SO₂(OR)₂ molecules and the differences in O–C–R angles and C–R bond lengths in R₃COX molecules. The lengths of these interligand radii can be determined either by calculating the molecular geometry or by deriving them from experimental geometries. The radii depend on the charge of the ligand, the sizes of the Y and Z groups and the angle A–X–Z. The relative sizes of these radii determine the preference for D_2d or S₄ geometries and the degree of distortion of the bond angles from the ideal tetrahedral angle.     

trans‐Bis(diethanolamine‐N,O)bis(saccharinato‐N)cadmium(II)

The structure of the title complex consists of isolated [Cd(C₇H₄NO₃S)₂(C₄H₁₁NO₂)₂] units. The Cd²⁺ cation lies on an inversion centre and is octahedrally coordinated by two N,O‐bidentate diethanol­amine (dea) and two N‐bonded saccharinate (sac) ligands [saccharin is 1,2‐benziso­thia­zol‐3(2H)‐one 1,1‐dioxide]. The dea ligands constitute the equatorial plane of the octahedron, forming two five‐membered chelate rings around the Cd^II ion, while the sac ligands are localized at the axial positions. The Cd—N_sac, Cd—N_dea and Cd—O_dea bond distances are 2.3879 (12), 2.3544 (14) and 2.3702 (13) Å, respectively. The H atoms of the free and coordinated hydroxyl groups of the dea ligands are involved in hydrogen bonding with the carbonyl and sulfonyl O atoms of the neighbouring sac ions, while the amine H atom forms a hydrogen bond with the free hydroxyl O atom. The individual mol­ecules are held together by strong hydrogen bonds, forming an infinite three‐dimensional network.