Tellurium-containing macrocycles

Synthetically is it relatively challenging to prepare heavier analogues of the thiacrowns containing Se and Te donors. The macrocycle [16] ane-Se4 is known and forms complexes with Ru(II) that can be oxidised to Ru(III) and isolated.24 Tellurium-containing macrocycles are limited to mixed Te/S donors such as [/j]ane-S2Te (n = 9, 11 and 12).25... 

The examined compound behaves as an N,Te-donor ligand also in analogous cobalt and copper complexes [922]. The N,Te-ligand environment is very likely for complexes 530 [923], 531 [924], adduct 532 [925], and tellurium-containing macrocyclic Schiff bases 533 [926] ... 

The tetraazamacrocycle 102 is the first known representative of tellurium-containing macrocycles. It was prepared in 80% yield by coupling bis-(o-formylphenyl) telluride (8IKGS121) with 1,2-diaminoethane [96JCS(D) 1203]. Reduction of 102 with NaBH4 gives rise to the tetraazamacrocyclic compound 103 [96JCS(D)1203]. 

Ch. 8 Tellurium-Containing Heterocycles with Hypervalent or Coordination Bonds to Tellurium Note. Macrocyclic and other complicated systems are not imdexed. 

R444 A. Panda, S. Panda, K. Srivastava and H. B. Singh, Chemistry of Selenium/ Tellurium-Containing Schiff Base Macrocycles , Inorg. Chim. Acta, [online computer file], 2011, 372, 17. 

Synthetic routes to macrocyclic ligands containing tellurium are still very limited, mainly because of the difficulties in sequentially introducing the necessary Te centres into organic fragments, the weakness of the Te C bonds and the unavailability or instability of many Te-containing analogues of the precursors for thio- and seleno-ether macrocycles. 

Several types of telluroether (diorganyl tellmide) ligands are known. They can be monodentate or polydentate, acyclic, cyclic, and macrocyclic as well as hybrid telluroether ligands containing other donor atoms in addition to tellurium. Complexes with tellmoether ligands have seen extensive research activity in recent years (for two most recent reviews, see Refs. 27 and 35). 

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