NEW HYPERVALENT ORGANOSELENIUM(II) HALIDES CONTAINING ORGANIC GROUPS WITH PENDANT ARMS

Monika Kulcsar, Anca Silvestru, Richard A. Varga and Cristian Silvestru

“Babes-Bolyai” University, Faculty of Chemistry & Chemical 
Engineering, 11 Arany Janos St., RO-400028 Cluj-Napoca, Romania;
E-mail:  kmonika@chem.ubbcluj.ro 

The new compounds [2,6-(Me2NCH2)2C6H3]2Se2 (1) and [2-{O(CH2)4NCH2}C6H4]2Se2 (2) were obtained using the ortho-lithiation of the tertiary amine, followed by insertion of elemental selenium and subsequent hydrolysis / air oxydation of the corresponding lithium organoselenolates. The cleavage of the Se-Se bond in 1 with SO2Cl2 (1:1 molar ratio) or elemental halogens afforded the isolation of [2,6-(Me2NCH2)2C6H3]SeX [X = Cl (3), Br (4), I (5)]. Similar reactions using the diselenide 2 gave the corresponding organoselenium halides, [2-{O(CH2)4NCH2}C6H4]SeX [X = Cl (6), Br (7)]. All compounds were investigated by means of 1H and 13C NMR spectroscopy and the assignment of the observed resonances was based on 2D NMR spectra. The solid-state molecular structures of 4 and 6 were established by single crystal X-ray diffraction. In the crystal of compound [2,6-(Me2NCH2)2C6H3]SeBr·H2O (4·H2O) an unusual dimer association is formed between two cations of the same type [either (R,R) or (S,S)], bromine atoms and water molecules. One bromine atom is bridging two selenium atoms and the interatomic Se(1)-Br(1) distances [3.662(2) Å] are consistent with an electrostatic anion-cation interaction. This interaction is directed trans to the selenium-carbon bond in the cation [C(1)-Se(1)-Br(1) 154.4(1)°], thus resulting in a distorted square-planar environment around the chalcogen atom. The water molecules bridge the Br(1) and Br(2) anions through halogen-hydrogen bonding [Br(1)H(1) 2.56(6) Å, (Br(2)H(2) 2.63(7) Å]. 
	      
 [2,6-(Me2NCH2)2C6H3]SeBr·H2O			    [2-{O(CH2)4NCH2}C6H4]SeCl