Tellurium–Nitrogen π‐Heterocyclic Chemistry – Synthesis, Structure, and Reactivity Toward Halides and Pyridine of 3,4‐Dicyano‐1,2,5‐telluradiazole

Abstract

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.

Double Chalcogen Bonds: Crystal Engineering Stratagems via Diffraction and Multinuclear Solid‐State Magnetic Resonance Spectroscopy

“…Specifically, the Se⋅⋅⋅N normalized contact ( N c ) ranges from 0.74 to 0.89 and the N−Se⋅⋅⋅N angles range from 161.70 to 175.34°. In both the cases, pyridyl moieties act as strong electron donors analogous to the previously reported complex 2⋅ PY (PY=pyridine) from Zibarev and co‐workers (CSD entry: TEGMID) . We further challenged 1 with the well‐known bidentate system 1,10‐phenanthroline (PHN), which is similar to ditopic bipyridine derivatives but is known to bind metals more tightly, since the chelating nitrogen donors are preorganized.…”

“…Similarly, the 125 Te isotropic chemical shift of 2 appears at 2332.8 ppm, close to the previously reported solution‐state value of 2442.46 ppm in [D 6 ]DMSO. DFT‐calculated J ( 125 Te, 14 N) values are on the order of 160 Hz. Unfortunately, it was not possible to measure any J values owing to the larger line widths obtained in the SSNMR spectrum.…”

Donor–Acceptor Complexes between 1,2,5‐Chalcogenadiazoles (Te, Se, S) and the Pseudohalides CN−and XCN−(X=O, S, Se, Te)

“…Such complexation is promising for the anion receptor chemistry . Coordination of two anions to one heterocycle is also possible, covering a potentially situation with two different anions. As such anions, F − and SeCN − were selected, in part due to the good NMR properties of the 19 F and 77 Se nuclei allowing NMR monitoring of the corresponding reaction mixtures.…”

“…The salts KOCN (96 %), KSCN (99 %), KSeCN (99 %), and cyclic polyether 18‐crown‐6 (99.5 %) were received from Aldrich. Compounds 1 a – 1 c and 7 were prepared by known procedures. Solvents were dried with common drying agents and distilled under argon.…”

Arsenic‐Mediated C−C Coupling of Cyanides Leading to Cyanido Arsazolide [AsC4N4]−

“…Only recently,n eutral triazarsole heterocycles were isolated either by insertion of isonitriles into arsatriazanediyls [As(m-NTer) 2 N] (Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl, D d(AsÀN) = 1.875 ) [21] and by making use of a[ 3 + +2] cycloaddition reaction between an arsaalkyne and an organic azide (species E d(AsÀN) = 1.839 ). [25][26][27] Interestingly Finally,D FT,N BO, and NRT computations at the pbe/aug-ccpvdz level (see the Supporting Information, DFT = density functional theory,N BO = natural bond theory,N RT = natural resonance theory) were carriedo ut to shed light into the bonding and formation of [AsC 4 N 4 ] À .S olvent effects, which are essential to stabilize charged ions, are incorporated using the integral equationf ormalism version of the polarizablec ontinuum model (PCM, solvent = acetonitrile). [25][26][27] Interestingly Finally,D FT,N BO, and NRT computations at the pbe/aug-ccpvdz level (see the Supporting Information, DFT = density functional theory,N BO = natural bond theory,N RT = natural resonance theory) were carriedo ut to shed light into the bonding and formation of [AsC 4 N 4 ] À .S olvent effects, which are essential to stabilize charged ions, are incorporated using the integral equationf ormalism version of the polarizablec ontinuum model (PCM, solvent = acetonitrile).…”