ic302454n_si_002.cif (354.23 kB)
Achiral and Chiral PNP-Pincer Ligands with a Carbazole Backbone: Coordination Chemistry with d8 Transition Metals
dataset
posted on 2013-02-18, 00:00 authored by Nora Grüger, Lara-Isabel Rodríguez, Hubert Wadepohl, Lutz H. GadeTwo new monoanionic PNP pincer type ligands have been
synthesized, the achiral 3,6-di-tert-butyl-1,8-bis((diphenyl-phosphino)methyl)-9H-carbazole CbzdiphosH (5) and the chiral 3,6-di-tert-butyl-1,8-bis(((2R,5R)-2,5-diphenylphospholan-1-yl)methyl)-9H-carbazole
CbzdipholH (7), both of which were initially prepared
as their borane complexes. The synthesis of CbzdiphosH is based on
the reaction between the key intermediate 1,8-bis(bromomethyl)-3,6-di-tert-butyl-9H-carbazole (3) and lithium diphenylphosphide-borane complex. The chiral ligand
CbzdipholH was prepared by treating 3 with lithium (2R,5R)-2,5-diphenylphospholanide-borane
complex and subsequent deprotection with diethylamine. The complexation
of the two ligands with nickel, palladium and rhodium was investigated,
for which the conformational behavior of the ligands was found to
be different. Although the arrangement of the donor atoms in all crystallographically
characterized complexes is approximately square planar, the carbazole
plane in Cbzdiphos complexes is inclined relative to the coordination
plane. On the other hand, a helical twist is observed in Cbzdiphol
complexes.