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Undecahalo‐ closo ‐undecaborates [B 11 Hal 11 ] 2–
Author(s) -
Volkov O.,
Paetzold P.,
Hu C.,
Kölle U.
Publication year - 2001
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200105)627:5<1029::aid-zaac1029>3.0.co;2-b
Subject(s) - chemistry , electrochemistry , bromine , reagent , electron transfer , crystal structure , crystallography , stereochemistry , photochemistry , electrode , organic chemistry
The closo ‐undecaborate A 2 [B 11 H 11 ] (A = NBzlEt 3 ) can be halogenated with excess N ‐chlorosuccine imide, bromine or iodine, respectively, to give the perhalo‐ closo ‐undecaborates A 2 [B 11 Hal 11 ] (Hal = Cl, Br, I). The chlorination in the 11 : 1 ratio of the reagents yields A 2 [B 11 HCl 10 ], whose subsequent iodination makes A 2 [B 11 Cl 10 I] available. The three type [B 11 Hal 11 ] 2– anions show only one and the two type [B 11 Cl 10 X] 2– anions (X = H, I) only two 11 B NMR peaks in the ratio 10 : 1, thus exhibiting the same degenerate rearrangement of the octadecahedral B 11 skeleton as is well‐known for [B 11 H 11 ] 2– . The crystal structure analysis of A 2 [B 11 Br 11 ] and A 2 [B 11 I 11 ] reveals a rigid octadecahedral skeleton in the solid state, up to 330 K, whose B–B bond lengths deviate more or less from the idealized C 2v gas phase structure, but are in good accordance with the distances of A 2 [B 11 H 11 ]. Electrochemical experiments elucidate the mechanism of the known oxidation of [B 11 H 11 ] 2– to give [B 22 H 22 ] 2– : A first one‐electron transfer is followed by the dimerization of the [B 11 H 11 ] – monoanion, whereas neutral B 11 H 11 , a presumably most reactive species, does not play a role as an intermediate. The electrochemical oxidation of [B 11 Hal 11 ] 2– anions also starts with a one‐electron transfer, which is perfectly reversible only in the case of Hal = Br. There is no electrochemical indication for the formation of [B 22 Hal 22 ] 2– . The neutral species B 11 Hal 11 should be a short‐lived, very reactive species.