S. N. Konchenko

Novel applications of functionalized 2,1,3- benzothiadiazoles for coordination chemistry and crystal engineering†

Two novel applications of functionalized 2,1,3-benzothiadiazoles for metal coordination chemistry and crystal engineering of organic solids are presented. 4-Amino-2,1,3-benzothiadiazole (1) forms a 2 : 1 complex with ZnCl2 (complex 2) and a 1 : 1 complex with 4-nitro-2,1,3-benzothiadiazole (3) (complex 4). The structures of compounds 1–4 were confirmed by single-crystal X-ray diffraction and studied by UV-Vis and IR spectroscopy, and DFT and QTAIM calculations. Complex 2 is the first structurally defined Zn complex with 2,1,3-benzothiadiazole ligands. In this complex, both molecules 1 are coordinated to Zn only by amino groups, thus revealing a novel type of coordination of this ligand to the metal center. According to 1H NMR data, complex 2 dissociates in CHCl3, THF or DMSO solutions. There are only a few examples of similar complexes, which are also considered to dissociate in solutions. In crystalline complex 4, molecules 1 and 3 form infinite alternating π-stacks connected by lateral S⋯N interactions between the neighboring stacks. Intermolecular S⋯N interactions are also observed in the crystals of individual 1 and 3 but the packing motifs are different from those in 4. DFT calculations predict a small charge transfer (CT, ∼0.02e at B97-D3 level) from 1 to 3 upon the formation of 4, which therefore is an unprecedented CT complex where both donor and acceptor moieties are the derivatives of the 2,1,3-benzothiadiazole ring system. This finding creates some new prospects for the crystal engineering of organic solids. Crystalline complex 4 is characterized by an intense CT absorption band with a maximum at ∼550 nm. However, according to DFT and QTAIM calculations the complex is weakly bonded and its formation is not observed in CH2Cl2 solution with 1H NMR and UV-Vis techniques.

Synthesis and structure of new homo-and heteroligand carbonyl cluster complexes with [Fe3(μ3-Q)(μ3-X)] core (Q = Se, Te; X = S, As)

New cluster complexes of iron [Fe3Q(AsCp*)(CO)9] (Q = Se, Te, Cp* = C5(CH3)5) are synthesized with the square pyramidal cluster core Fe3QAs. A suitable procedure of the synthesis of known heterochalcogenide [Fe3QS(CO)9] clusters is developed. Monosubstituted [Fe3Q(AsCH3)(CO)8(PPh3)] and disubstituted [Fe3Q(AsCH3)(CO)7(PPh3)2] clusters formed in the reactions of [Fe3Q(AsCH3)(CO)9] with PPh3 are studied. In monosubstituted clusters, the phosphine ligand is coordinated in the axial position to the Fe atom in the base of the Fe3QAs square pyramid, while in disubstituted clusters, both phosphine ligands coordinate the Fe atoms in the pyramid base, one ligand being in the axial and another one in the equatorial position. The NMR data support the possibility of migration of the Fe-Fe bonds in a triangle in the cluster core in the case of disubstituted clusters.

The First Lanthanide Complexes with a Redox-Active Sulfur Diimide Ligand: Synthesis and Characterization of [LnCp*2(RN=)2S], Ln=Sm, Eu, Yb; R=SiMe3

The first lanthanide complexes with a redox-active sulfur diimide ligand, [LnCp*2 (Me3 SiN=)2 S] (Ln=Sm, Eu, Yb; Cp*=η5 -C5 Me5 ), are reported. The complexes were synthesized by using [LnCp*2 (THF)2 ] and (Me3 SiN=)2 S and have been thoroughly characterized by single-crystal X-ray diffraction, EPR spectroscopy, UV/Vis/NIR electronic absorption spectroscopy and SQUID magnetometry. The results, as interpreted by CASSCF/SOC-RASSI calculations providing a non-perturbative treatment of spin-orbit coupling, indicate that these paramagnetic complexes are best described as Ln3+ and [(Me3 SiN=)2 S]-. adducts. As such, these complexes contain the first isolated and structurally characterized acyclic [(RN=)2 S]-. radical anions.

Synthesis and structure of the cluster Fe2Mo2(μ3-Se)(μ3-AsMe)(μ3-Co)(μ-Co)(Co)5(η5-Cp)2

The reaction of (Et4N)2[Fe3(μ3-Se)(Co)9] with MeAsI2 afforded the [Fe3(μ3-Se)(μ3-AsMe)(Co)9] cluster, which was characterized by1H NMR and IR spectroscopy and elemental analysis. The reaction of the resulting compound with the dimeric, complex [η5-CpMo(CO)3#x005D;2 inm-xylene upon refluxing gave the heterometallic cluster Fe2Mo2(μ3-Se)(μ3-AsMe)(μ3-Co)(μ-Co)(Co)5(η5-Cp)2, whose structure was established by X-ray diffraction analysis.

Nature of Bonding in Donor–Acceptor Interactions Exemplified by Complexes of N‐Heterocyclic Carbenes with 1,2,5‐Telluradiazoles

Comprehensive structural, spectroscopic, and quantum chemical analyses of new donor-acceptor complexes between N-heterocyclic carbenes and 1,2,5-telluradiazoles and a comparison with previously known complexes involving tellurenyl cations showed that the dative C-Te bonds cannot be solitarily described with only one Lewis formula. Canonical Lewis formulas that denote covalency and arrows emphasizing ionicity complement each other in varying extents. Evaluation of the relative weights of these resonance forms requires proper bonding description with a well-balanced toolbox of analytical methods. If for conciseness only, one resonance form is used, it must be the most significant one according to the analytical evaluation. If unclear, all significant resonance forms should be displayed.

Ribbed-monofunctionalized iron(II) clathrochelate with tert-butyl sulfide substituents: Synthesis, structure, and thermochemical transformations

A ribbed-monofunctionalized macrobicyclic iron(II) complex with tert-butyl sulfide substituents has been prepared via nucleophilic substitution of its dichloroclathrochelate precursor with tert-butylthiolate ion. This new complex has been characterized using elemental analysis, IR and multinuclear NMR spectroscopy, and the single crystal X-ray diffraction. Its thermal destruction occurs with release of isobutylene and polyunsaturated hydrocarbons giving iron borate, iron fluoropolyborate, and iron nitride as follows from combined thermal analysis and X-ray powder diffraction data.

The first seven-electron triangular tungsten sulfide cluster

A new cluster complex [W3S4(Dppe)3Br3] · 3THF (Dppe = Ph2PCH2CH2PPh2), the first example of a triangular tungsten cluster with a seven-electron core, was synthesized. The molecular and crystal structures of the compound were determined by X-ray diffraction.

Novel luminescent β-ketoimine derivative of 2,1,3-benzothiadiazole: synthesis, complexation with Zn(II) and photophysical properties in comparison with related compounds

A novel β-ketoimine-functionalized 2,1,3-benzothiadiazole (4-(2,1,3-benzothiadiazole-4-ylamino)pent-3-en-2-one, L2H) was synthesized and used as chelating ligand for the complexation with Zn(II) (complex ZnL2). The spectroscopic and photophysical properties of L2H and ZnL2 as well as those of previously described 4-amino-2,1,3-benzothiadiazole (L1) and its complex ZnL1 have been thoroughly studied in the crystalline state and solution. The UV-Vis absorption spectra of free ligands L1, L2H and its deprotonated form L2−, and complexes ZnL1 and ZnL2 were assigned on the basis of TD-DFT calculations. In contrast to ZnL2 having conventional single-band fluorescence, ZnL1 demonstrates a broad double-band purple-white fluorescence spanning the entire visible region. On the basis of careful spectroscopic studies the second band of this unusual fluorescence spectrum was attributed to the presence of traces of free ligand L1 in the crystals of complex ZnL1. The energy transfer from the excited state of ZnL1 to a free ligand L1 was revealed.

Chalcogen arsenide clusters of iron with a functional carboxyl group: Synthesis, structures, and thermolysis

The carbonyl clusters [Fe3(μ3-Q)(μ3-AsR)(CO)9] (Q = Se and Te; R = meta- and para-HOOCC6H4) were obtained from the salts K2[Fe3(μ3-Q)(CO)9] and organoarsenic diiodides RAsI2 prepared by reducing iodination of arsonic acids RAsO(OH)2 according to a novel method. The structures of the clusters were identified by X-ray diffraction. The crystal packing motifs of the dimers of the cluster molecules and their relationship with the solubility of the clusters are discussed. The sequential steps of the thermolysis (decarbonylation, decarboxylation, and decomposition of the organic fragment) of the clusters were studied. The presence and location of the carboxyl group does not influence the decarbonylation temperature.

Heterometallic heterochalcogenmethylarsenide clusters: Synthesis, molecular structures, and thermolysis

Reactions of the arsinechalcogenide complexes [Fe3(μ3-X)(μ3-AsCH3)(CO)9] (X = Se (Ia) or Te (Ib)) with (PPh3)2Pt(PhC≡CPh) (transmetalation reaction) and Cp2Cr2(SCME3)2S (Cp = π-C5H5) (photochemical reaction) gave the heterometallic (heterochalcogen)(methylarsine) clusters [(PPh3)2Pt(μ3-X)(μ3-AsCH3)Fe2(CO)6] (II and III, respectively), as well as Fe3(μ3-X)(μ3-AsCH3)(CO)8(C5H5)2Cr2(μ3-S)(μ2-StBu)2 (IV and V, respectively). The structures of complexes II, IV, and V were determined by X-ray diffraction analysis. Thermolysis of all the complexes yielded no metal carbides or oxides.