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

Abstract

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.

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

“…As in previous cases, the main interaction forming the D–A Te−X bonds in 2 – 6 (X=C, N, S, Se) is the negative hyperconjugation featuring transfer of electron density from the lone‐pair MOs of the pseudohalides to the σ*‐antibonding N−E MOs (E=chalcogen) of the heterocycles (for applying some modern descriptors, see Ref. ). In accordance with the experiment, for all studied complexes the calculated Gibbs free energies of their formation in MeCN are less than −5 kcal mol −1 , which means that the complexes are thermodynamically more favorable than the starting material 1 a and the pseudohalides (Table ).…”

Radical Anions, Radical‐Anion Salts, and Anionic Complexes of 2,1,3‐Benzochalcogenadiazoles

“…ref. ). This might indicate dissociation of weakly bonded [ 3 ‐Te 2 ] 2− and [ 3 ‐Te 4 ‐ 3 ] 2− into 3 and [Te 2 ] 2− and [Te 4 ] 2− , respectively, in solution.…”

“…Compounds 1 , 2 , 18‐crown‐6, and TeCl 4 were received from Aldrich, and 1 and 2 were additionally purified by vacuum sublimation. Reducing agent KC 8 was prepared by a known method, and compound 3 by a modified procedure . Chemical reductions were performed under argon by using common vacuum‐line, Schlenk, sealed‐ampoule, and glovebox techniques.…”

“…Synthesis of 3 (modified procedures) : a) At ambient temperature, a solution of 1,2‐diaminobenzene (0.406 g, 3.76 mmol) in toluene (60 mL) was added to a stirred suspension of TeCl 4 (1.01 g, 3.73 mmol) in toluene (60 mL). Then, an excess of Et 3 N (3.0 mL, 22 mmol) was added.…”

Reappraising Schmidpeter's bis(iminophosphoranyl)phosphides: coordination to transition metals and bonding analysis

“…The nature of the C-P bond in these compounds has been rather controversial, [12][13][14][15][16] partly because evidence of C-P bond cleavage in CDP and related compounds is scarce: 17 indeed, dative covalent bonds are generally perceived as weak, compared to normal covalent bonds. 14,18 However, the dening feature of dative covalent bonds is their preference for heterolytic bond cleavage in the gas phase (or inert solvents), [18][19][20][21][22][23][24] which does not equate with bond weakness.…”