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N ‐Alkylation of Ammine—Undecahydro‐ Closo ‐dodecaborate(1−)
Author(s) -
Peymann Toralf,
Lork Enno,
Schmidt Martin,
Nöth Heinrich,
Gabel Detlef
Publication year - 1997
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19971300619
Subject(s) - chemistry , triclinic crystal system , alkylation , iodide , steric effects , monoclinic crystal system , medicinal chemistry , alkyl , orthorhombic crystal system , crystal structure , ethyl iodide , crystallography , stereochemistry , organic chemistry , catalysis
The reactions of the ammine‐undecahydro‐ closo ‐dodecaborate(1−) anion with alkyl halides have been studied in detail. The degree of alkylation of the nitrogen was found to be dependent upon the steric demands of the alkyl groups. The derivatives were characterized by NMR and infrared spectroscopy. Four compounds were crystallized for single crystal X‐ray diffraction studies. The tetrahedral coordination of the nitrogen atom of the bis‐alkylated derivatives was found to deviate towards planarity with increasing steric hindrance of the substitutents. ‐ The syntheses, crystal structures, and spectral properties of four N ‐alkyl derivatives of [H 3 NB 12 H 11 ]‐, ammine—undecahydro‐ closo ‐dodecaborate(1−) ( 3 ), are reported. Alkylation of 3 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as base. This led to orthorhombic crystals of [N( n C 4 H 9 4 ][(CH 3 CH 2 ) 3 NB 12 H 11 ] ( 4 ). The reaction of 3 with benzyl chloride resulted in the bisbenzylated product, isolated as triclinic crystals of [PPN][(C 6 H 5 CH 2 ) 2 NHB 12 H 11 ] ( 5 ). The alkylation of 3 with 2‐bromopropane gave a mixture of the mono‐ and bisalkylated products. The monoalkylated derivative [PPN][(CH 3 ) 2 CH)NH 2 – 12 H 11 ] ( 6 , crystallized in the triclinic space group p 1) and the bisalkylated product [PPN]{[(CH 3 ) 2 NHB 12 H 11 ) ( 7 , monoclinic, P2 1 ./c) were separated on the basis of their different water solubilities. The solid‐state structures of the compounds 4–7 revealed a slight distortion of the B 12 icosahedron. The length of the B(1)–N(1) bond was found to be dependent on the steric requirements of the attached amine, e.g. primary amine < secondary amine < tertiary amine. This is demonstrated by the variation in the BN bond length; from 157.8(2) pm for 6 , 158.5(5) pjm for 5 , 160.0(3) pm for 7 , to 163.7(6) pm for 4 .