Synthesis of N,C Bound Sulfur, Selenium, and Tellurium Heterocycles via the Reaction of Chalcogen Halides with −CH3 Substituted Diazabutadiene Ligands

Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-imides

The vapor deposition of many molybdenum-containing films relies on the delivery of volatile compounds with the general bis(tert-butylimido)molybdenum(VI) framework, both in atomic layer deposition and chemical vapor deposition. We have prepared a series of (^tBuN)₂MoCl₂ adducts using neutral N,N'-chelates and investigated their volatility, thermal stability, and decomposition pathways. Volatility has been determined by thermogravimetric analysis, with the 1,4-di-tert-butyl-1,3-diazabutadiene adduct (5) found to be the most volatile (1 Torr of vapor pressure at 135 °C). Thermal stability was measured primarily using differential scanning calorimetry, and the 1,10-phenanthroline adduct (4) was found to be the most stable with an onset of decomposition of 303 °C. We have also investigated molybdenum compounds with other alkyl-substituted imido groups: these compounds all follow a similar decomposition pathway, γ-H activation, with varying reaction barriers. The tert-pentyl, 1-adamantyl, and a cyclic imido (from 2,5-dimethylhexane-2,5-diamine) were systematically studied to probe the kinetics of this pathway. All of these compounds have been fully characterized, including via single-crystal X-ray diffraction, and a total of 19 new structures are reported.

Antimony diiminopyridine complexes

The stoichiometric reactions of antimony trichloride, trimethylsilyl trifluoromethanesulfonate, and diiminopyridine ligands lead to the formation of N,N',N''-chelated SbCl₂ cationic complexes. Methyl and phenyl substituents on the imine carbons of the ligand yielded structures with a lone pair on antimony and the hydrogen substituted variant was notably different as it forms a Menshutkin complex with meta-xylene in the solid-state.

Competing Effects of Chlorination on the Strength of Te⋅⋅⋅O Chalcogen Bonds Select the Structure of Mixed Supramolecular Macrocyclic Aggregates of Iso-Tellurazole N-Oxides

Chlorination of 3-methyl-5-phenyl-1,2-tellurazole-2-oxide yielded the λ⁴ Te dichloro derivative. Its crystal structure demonstrates that the heterocycle retains its ability to autoassociate by chalcogen bonding (ChB) forming macrocyclic tetramers. The corresponding Te⋅⋅⋅O ChB distances are 2.062 Å, the shortest observed to date in aggregates of this type. DFT-D3 calculations indicate that while the halogenated molecule is stronger as a ChB donor it also is a weaker ChB acceptor; the overall effect is that the ChBs in the chlorinated homotetramer are not significantly stronger. However, partial halogenation or scrambling selectively yield the 2 : 2 heterotetramer with alternating λ⁴ Te and λ² Te centers, which calculations identified as the thermodynamically preferred arrangement.

Isolation of the novel example of a monomeric organotellurinic acid

The synthesis of the first example of a monomeric, stable organotellurinic acid is reported by utilizing the σ-hole participation of the Te atom with the N atom of the 2-(2′-pyridyl)phenyl moiety.

Chalcogen bonding in synthesis, catalysis and design of materials

Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons.

Crystal structure of rac-(3aR*,9aS*)-4,4,4-tri-chloro-1,2,3,3a,4,9a-hexa-hydro-4λ(5),9λ(4)-cyclo-penta-[4,5][1,3]tellurazolo[3,2-a]pyridine

The title compound, C₁₀H₁₂Cl₃NTe, crystallizes with two crystallographically independent mol­ecules (A and B) in the asymmetric unit. In each case, the coordination around the Te atom is distorted square-pyramidal, with the equatorial plane composed of the three Cl atoms and the C atom of the pyridinium ring. The Te atom is displaced from the mean-square plane by 0.1926 (7) and 0.1981 (8) Å, in mol­ecules A and B, respectivly, away from the apical C atom. The bond lengths from the Te atom to the two Cl atoms arranged trans to each other [2.5009 (7)/2.5145 (7) and 2.5184 (7)/2.5220 (8) Å in mol­ecules A and B, respectivly] are substan­ti­ally shorter than the third Te—Cl distance [2.8786 (7) and 2.8763 (7) Å in mol­ecules A and B, respectivly]. The 1,3-tellurazole ring is almost planar (r.m.s. deviations of 0.042 and 0.045 Å in mol­ecules A and B, respectivly). The cyclopentane rings in both molecules A and B adopt envelope conformations with the carbon atom opposed to the (Te)C—C(N) bond as the flap. In the crystal, mol­ecules form centrosymmetric 2 + 2 associates via Te⋯Cl inter­actions [3.3993 (7) and 3.2030 (7) Å]. As a result of these secondary inter­actions, the Te atom attains a strongly distorted 5 + 1 octa­hedral environment. Further, the 2 + 2 associates are bound by weak C—H⋯Cl hydrogen bonds into a three–dimensional framework.