The reaction of 2,3‐diaminomaleonitrile with TeX4 (X = Cl, Br) in the presence of pyridine (Py) and/or triethylamine (Et3N) provided 3,4‐dicyano‐1,2,5‐telluradiazole (1), which was isolated neat and as stable adducts with pyridine, chloride, and bromide, namely, 1·2Py, (PyH)(1·Cl), (PyH)2(1·2Cl), (Et3NH)(1·Cl), (PyH)(1·Br), and (PyH)2(1·2Br). The molecular and supramolecular structures of these compounds were investigated by X‐ray crystallography. In the solid state, intermolecular associations through secondary Te···N interactions as well as N–H···X and N–H···N hydrogen bonding (X = Cl, Br) were observed. For (PyH)(1·Br), two polymorphs were found. The bonding situation of 1 and its pyridine and chloride adducts were investigated by MP2 calculations supplemented with the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. The π symmetry of the frontier molecular orbitals (MOs) of 1 are preserved in the 1·2Py, (1·Cl–), and (1·2Cl–) adducts. In the chloride adducts, the highest occupied molecular orbital (HOMO) can be described as an antibonding combination of the HOMO of 1 with the 3p atomic orbitals (AOs) of the chloride ions, whereas the lowest occupied molecular orbital (LUMO) resembles that of the parent 1. The charge transfer onto the heterocycle in the adducts increases in the order 1·2Py, (1·2Cl–), and (1·Cl–). QTAIM analyses of the adducts in the gas phase reveal closed‐shell interactions, whereas NBO analyses indicate negative hyperconjugation as the main formation pathway in these complexes. This description agrees with the Alcock model suggested for secondary bonding interactions between atoms of heavy p‐block elements and atoms with lone pairs.

New products of coordination of anions X– (X = F, I, PhS) to the Te atom of 3,4-dicyano-1,2,5-telluradiazole (1) were synthesized in high yields and characterized by X-ray diffraction (XRD) as the salts [(Me2N)3S]+[1-F]− (9), [K(18-crown-6)]+[1-I]− (10), and [K(18-crown-6)]+[1-SPh]− ·THF (11), respectively. In the crystal lattice of 10, I atoms are bridging between two Te atoms. The bonding situation in anions of the salts 9–11 and some other adducts of 1,2,5-chalcogenadiazoles (chalcogen = S, Se, Te) and anions X– (X = F, Cl, Br, I, PhS) was studied using DFT, QTAIM, and NBO calculations, for 9–11 in combination with UV–vis, IR/Raman, and MS-ESI techniques. In all cases, the nature of the coordinate bond is negative hyperconjugation involving the transfer of electron density from X– to the heterocycles. The energy of the bonding interaction varies in a range from ∼30 kcal mol–1 comparable with energies of weak chemical bonds (e.g., internal N–N bond in organic azides) to ∼86 kcal mol –1 comparable with an energy of the C–C covalent bonds. The thermodynamics of the anions’ coordination to 1 and their Se and S congeners was also studied by quantum chemical calculations. The general character of this reaction and favorable thermodynamics in the case of heavier chalcogens (Se, Te) were established. Comparison with available data on acyclic analogues, i.e. the chalcogen diimines RNXNR, reveals that they also coordinate various anions but in addition reactions across XN (X = S, Se, Te) double bonds. Attempts to prepare the anion [1-TePh]− led to disintegration of 1. The only unambiguously identified product was a rather rare tellurocyanate that was characterized by XRD and elemental analysis as the salt [K(18-crown-6)]+[TeCN]− (13).

[{(eta(5)-C(5)Me(5))(2)Sm}(4)P(8)], a molecular polyphosphide of the rare-earth elements having a realgar core structure, was synthesized by a one-electron redox reaction of divalent samarocen and white phosphorus.

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo [3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were prepared in the form of single crystals and structurally defined by X-ray diffraction as 1·2 and 1·3 2 , respectively. Starting compound 2 was synthesized by a new efficient method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure and UV-vis spectral properties of complexes 1·2 and 1·3 2 were studied by means of DFT 2 calculations. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1·2 and 0.40 eV for 1·3 2 . Both complexes displayed photoconductive effects with increased conductivity under white-light illumination.3

Triple-and multidecker sandwich complexes have been discussed in the last decades for their unique electrical and magnetic properties. The organic spacer between the metals may facilitate intermetallic electronic communication, which has a high potential for molecular electronics.[1] A number of one-dimensional organometallic sandwich molecular wires (SMWs) have been extensively studied. Thus, the multilayer vanadium-arene (Ar) organometallic complexes [V n (Ar) m ], which can be produced in a molecular beam by laser vaporization, are a class of one-dimensional molecular magnets.[2] Ferrocene-based molecular wires have been synthesized in the gas phase and characterized by mass spectroscopy.[3] It was calculated that these compounds have half-metallic properties with 100 % negative spin polarization near the Fermi level in the ground state.[4] In contrast to this investigation in the gas phase, studies on related organometallic triple-and multidecker sandwich complexes containing f-block elements (lanthanides or actinides) in condensed phase remain rare;[5] studies were mostly on the cyclooctatetraene ligand and its derivatives. The only rare-earth-element triple-decker complex with heterocycles is the low-valent scandium 1,3,5-triphosphabenzene complex [{(h 5 -P 3 C 2 tBu 2 )Sc} 2 (m-h 6 :h 6 -P 3 C 3 tBu 3 )], which was obtained by cocondensation of scandium vaporized in an electron beam with an excess of the phosphaalkyne tBuCP.[6] Apart from organometallic compounds, triple-and multidecker sandwich complexes of the 4f elements consisting of "salen" type Schiff base ligands, [7] phthalocyanines, and porphyrins have been extensively studied because these compounds exhibit tunable spectroscopic, electronic, and redox properties, and different extents of intramolecular p-p interactions.[8] Despite these promising physical properties further investigations on 4f elements based triple-and multidecker sandwich complexes are obviously hampered by the limited variety of ligands that have been attached to the metal centers to date. Based on these considerations, we present herein mixed d/f-block-metal triple-decker complexes with a purely inorganic all-phosphorus middle deck.In contrast to d-block chemistry, where purely inorganic ring systems of Group 15 elements such as P 5 and P 6 , [9] As 5 , [9c] and Sb 5 [10] are well-established, there is no analogy with the fblock elements to date. On the other hand, it was shown only recently that rare-earth elements can stabilize highly reactive main-group species such as N 2 3À .[11] Although some heavier Group 15-lanthanide compounds, such as phosphides (Ln À PR 2 ), [12] arsenides (Ln À AsR 2 ), [12d, 13] stibides (Ln À Sb 3 ), [14] and bismutides (LnÀBiÀBiÀLn) [15] are known, the first molecular polyphosphide of the rare-earth elements, [(Cp* 2 Sm) 4 P 8 ] (Cp* = h 5 -C 5 Me 5 ), was recently synthesized. [16] The structure of the complex is very rare and can be described as a realgartype P 8 4À ligand trapped in a cage of four samarocenes. As no triple-decker sandw...