Dimethyl tellurium (IV) derivatives: synthesis, spectroscopic characterisation and structures of Me2TeBr2 and Me2Te(OCOC6H5)2

Modification of supramolecular assemblies based on C4H7(CH3)Te heterocycle and cooperative participation of intermolecular I···I, Te···I, Te···O secondary bonds; C(sp3)–H···O and C(sp2)–H···O hydrogen bonds

“…Symmetry transformations used to generate equivalent atoms and Te (2) pair. This type of geometry has been observed previously in a variety of acyclic-and cyclic organotellurium complexes [6,[13][14][15][16].…”

“…O(1A)-Te-O(1A)# angle of 160.2(8) • deviates considerably from linearity with both oxygen atoms pushed away from the equatorial lone pair at tellurium. This fairly large deviation from linearity in the O(1A)-Te-(O1A)# angle has also been observed in acyclic dialkyl [14] and diaryl tellurium dicarboxylates [13,15,16] and may be attributed to the presence of Te · · · O secondary bonds [20]. Due to Te · · · O secondary bonds, Te atom is hepta coordinated with an unshared electron pair at the vertex situated in the trans position to one of the -CH 2 groups attached to tellurium (the secondary bond itself is in the trans position to the other >CH-group attached to Tellurium).…”

“…5. Of the three methylene and one methene groups in the heterocycle, one methylene and one methene carbon atoms of the C 4 H 7 groups are bonded to the Te(IV) atom with the Te-C(1C) and Te-C(4C) bond lengths 2.150(4) and 2.165 (6) (1) • deviates considerably from linearity with both oxygen atoms pushed away from the equatorial tellurium lone pair, similar to deviations from linearity observed in acyclic dialkyl [14] and diaryl tellurium dicarboxylates [13,15,16] and may be attributed to the presence of Te · · · O secondary bonds [20].…”

“…The respective angles I(21) · · · Te(1)-C (14) and I(21) · · · Te(1)-C(11) are 163.1(2) • and 87.8(2) • and the respective angles are I(11) · · · Te(2)-C(24) and I(11) · · · Te(2)-C(21) are 166.9(2) • and 93.3(2) • . Similar coordination environment for tellurium are found in di(trifluroacetato)diphenyl tellurium [13] and in cis-2-ethoxycycloheptyl tribromotellurium [17] in which the unshared electron pair is trans to the organic group.…”

“…The Te · · · O distance 3.053 Å is shorter than the sum of van der Waals radii (3.60 Å) [13,23] and longer than the sum of covalent radii (2.03 Å) [22] and thus definitely corresponds to a secondary bond [20] but it is much weaker than in the complex cis-2-ethoxycycloheptyl tribromotellurium [17] where the Te · · · O distance is 2.49 Å and in (CH 3 ) 2 Te(OCOC 6 H 5 ) 2 [14] where it is 2.224 Å but is comparable to the Te · · · O distances (2.95-3.02 Å) in (p-MeOC 6 H 4 ) 2 Te(OCOCH 3 ) 2 [15], (2.99-3.03 Å) in (C 6 H 5 ) 2 Te(OCOCF 3 ) 2 [13], and 3.083 Å in C 4 H 8 Te(OCOC 6 H 5 ) 2 [6]. These Te · · · O secondary bonds join the molecules to form trimeric supramolecular associations in which Te atom is effectively seven coordinate similar to the coordination shown by tellurium through Te · · · O secondary bonds in C 4 H 8 Te(OCOC 6 H 5 ) 2 [6] and through Te · · · S secondary bonds in S, [26].…”