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Synthesis of a Novel Potential Tridentate Anthracene Ligand, 1,8‐Bis(dimethylamino)‐9‐bromoanthracene, and Its Application as Chelate Ligand for Synthesis of the Corresponding Boron and Palladium Compounds
Author(s) -
Yamashita Makoto,
Kamura Kumiko,
Yamamoto Yohsuke,
Akiba Kinya
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020703)8:13<2976::aid-chem2976>3.0.co;2-g
Subject(s) - ligand (biochemistry) , chemistry , palladium , anthracene , bromide , singlet state , medicinal chemistry , metal , boron , lithium (medication) , crystal structure , chelation , stereochemistry , crystallography , photochemistry , inorganic chemistry , organic chemistry , catalysis , medicine , biochemistry , physics , receptor , nuclear physics , excited state , endocrinology
A novel potential tridentate ligand, 1,8‐bis(dimethylamino)‐9‐bromoanthracene, was synthesized. The key steps are as follows: 1) dimethylamination of 1,8‐dibromo‐9‐methoxyanthracene by a modified Buchwald's method to afford 1,8‐bis(dimethylamino)‐9‐methoxyanthracene, and 2) reduction of the methoxy group by LDBB (lithium di‐ tert ‐butylbiphenylide) followed by treatment with BrCF 2 CF 2 Br. The corresponding 1,8‐bis(dimethylamino)‐9‐lithioanthracene, which should be a useful versatile tridentate ligand, could be generated by treatment of the bromide with one equivalent of n BuLi. The lithioanthracene reacted with B ‐chloroborane derivatives to give three 9‐boryl derivatives. Although we recently reported that the crystal structure of 1,8‐dimethoxy‐9‐ B ‐catecholateborylanthracene was a symmetrical compound with the almost identical two OB distances (2.379(2) and 2.441(2) Å), the newly prepared 1,8‐bis(dimethylamino)‐9‐borylanthracene derivatives clearly have unsymmetrical structures with coordination of only one NMe 2 group toward the central boron atom. However, the energy difference between the unsymmetrical and symmeterical structures was found to be very small based on 1 H NMR measurements, in which symmetrical anthracene patterns in the aromatic region (two kinds of doublets and a triplet) and a sharp singlet signal of the two NMe 2 groups were observed even at −80 °C. 1,8‐Bis(dimethylamino)‐9‐bromoanthracene itself can be a versatile ligand for transition metal compounds. In fact, direct palladation of the bromide took place by the reaction with [Pd 2 (dba) 3 ]⋅CHCl 3 in THF to give the 9‐palladated product. X‐ray crystallographic analysis of the Pd compound showed that the square planar palladium atom was coordinated in a symmetrical fashion by both NMe 2 groups (PdN bonds are 2.138(5) and 2.146(5) Å).