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Triaminoboranes and Their Metallation to N ‐Lithiotriaminoboranes
Author(s) -
Braun Ulrike,
Habereder Tassilo,
Nöth Heinrich,
Piotrowski Hans,
Warchhold Marcus
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200205)2002:5<1132::aid-ejic1132>3.0.co;2-u
Subject(s) - chemistry , deprotonation , borane , medicinal chemistry , bond cleavage , protonation , stereochemistry , organic chemistry , catalysis , ion
In order to study the competition between deprotonation, borate formation, and B−N bond cleavage, six triaminoboranes bearing 1−3 NH functions were treated with butyllithium. The 2‐anilino‐1,3,2‐diazaborolidine 1 was cleanly deprotonated, but the resulting N ‐lithio compound could not be crystallized. However, as a result of slow hydrolysis, the lithium 2‐oxido derivative 7 was isolated in low yield as a dimeric ether solvate. Double deprotonation of 2‐(dimethylamino)‐1,3,2‐benzodiazaborolidine ( 9 ) was accompanied by B−N bond cleavage. The dilithio derivative reacted with Me 3 SiCl to produce 2‐dimethylamino‐1,3‐bis(trimethylsilyl)‐1,3,2‐benzodiazaborolidine ( 11 ). Similarly, dianilino(diphenylamino)borane ( 2 ) was readily deprotonated to the insoluble dilithium compound. B−N bond cleavage also occurred, however, and the solvates Ph 2 NLi·dme ( 13 ) and Ph 2 NLi·2py ( 14 ) were isolated. These are dimeric, the former with a planar Li 2 N 2 ring, the latter possessing an N−Li−N−Li chain structure. Triply metallated trianilinoborane ( 15 ) crystallized as dimeric B(NLiPh) 3 ·LiCl·(OEt 2 ) 3 ( 15A ). Treatment of trianilinoborane ( 3 ) with LiBu in 1:1 and 1:2 ratios showed that the deprotonation was accompanied by the formation of anilino(butyl)borates. Treatment of the dilithio derivative of 3 with Me 3 SnCl afforded B[N(SnMe 3 )Ph] 3 ( 23 ), a result of substituent exchange. Tris(2‐pyridylamino)borane ( 4 ), with a planar skeleton, reacted with BuLi both by deprotonation and by B−N bond cleavage. The metallated triaminoborane crystallized as dimeric Li 4 B(NR*) 3 NHR*(THF) 3 ( 18 ; R* = 2‐pyridyl). Tris(8‐quinolylamino)borane ( 5 ) can also be triply lithiated according to 11 B and 7 Li NMR spectroscopic data. X‐ray determination of the structures of compounds 1 − 3 showed the absence of N−H ··· N hydrogen bonding, which seems to be responsible for the planar structures of compounds 4 and 5 . The planarity of the BN 3 units in 3 and 4 was retained in the trilithiated compounds 15A and 18 , as ascertained by X‐ray structure determination. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)