Lewis Base Sequestered Chalcogen Dihalides: Synthetic Sources of ChX₂ (Ch=Se, Te; X=Cl, Br)

Abstract

The synthesis and comprehensive characterization of a series of base-stabilized ChX(2) (Ch = Se, Te; X = Cl, Br) is reported using aryl-substituted diazabutadiene and 2,2'-bipyridine (bipy) as the ligands. In stark contrast to free ChX(2) the complexes display excellent thermal stability. Their use as viable ChX(2) reagents that may be stored for later use is demonstrated in principle. The syntheses are simple and high-yielding from commercially available or easily synthesized reagents. The bipy complexes are exceedingly rare examples of this ubiquitous ligand being utilized within Group 16 chemistry; the Se examples are the first to be characterized by X-ray crystallography, and the Te species are only the second.

The Future of Main Group Chemistry

“…[69] In related work the stabilization of labile (or unknown) binary chalcogen halides EX 2 (E ¼ Se, Te; X ¼ Cl, Br) has been achieved by coordination to 2,2 0 -bipyridine (27). [70] The study of synthetic applications of these potentially useful new reagents is in its infancy.…”

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

“…[7] All other relevant compoundsi ncluding [RTe(NHC)] + (4a 2.091(8) ; [8] 4c 2.117(5) ; [9] Scheme 2), [(NHC) 2 Te] 2 + (2.136(8), 2.138(5) ), [6] (NHC)Te X 2 (X = Cl, 2.103(3) ; [10] X = I, 2.106(5) [11a] ), and (NHC)[TeN(OÀBF 3 ) = C(H)(C 6 H 4 )] (2.179(9) ) [11b] possessm uch shorter CÀTe bond lengths. The CÀTe bond lengths of 1a·2 (2.343(4) )a nd 1a·3 (2.524(2)a nd 2.530(2) ;t wo independent conformers) are significantly longert han the sum of single-bond covalent radii for Te and C( 2.12 ).…”

Dicationic Tellurium Analogues of the Classic N‐Heterocyclic Carbene

“…The 2,2'-bipyridine chelate of TeCl 2 (4) has been demonstrated to be a stable and viable source of TeCl 2 . [35] Attempted ligand exchange with Dipp 2 DAB resulted in no reaction, but the 1:1 stoichiometric reaction of the more Lewis basic Cy 2 DAB (Cy = cyclohexyl) with 4 resulted in the immediate deposition of a dark-yellow powder. The yellow powder was found to be completely insoluble in organic solvents, precluding analysis through NMR spectroscopy, similar to what had been found for the SeCl 2 -Cy 2 DAB adduct.…”

“…[28][29][30][31][32][33][34] Recently a few groups have used this strategy to deliver this otherwise unstable electrophilic Te II source. [35][36][37] Therefore, the proposed synthetic route to the tellurium NHC analogues is coordination by a DAB ligand to TeX 4 , followed by reduction and halide abstraction to give the dication. We have previously demonstrated the coordination of the tertbutyl-DAB ligand to TeBr 4 ; in this case, reduction was spontaneous upon attempted halide abstraction giving a 1,2,5-telluradiazolium cation, due to the facile elimination of tert-butylbromide.…”