Synthesis and Coordination Chemistry of Phosphinite
POCN Pincer Type Ligands
Medet Segizbayev*, Kristina Gudun, Mannix Balanay, and Andrey Khalimon**
Department of Chemistry, School of Science and Technology, Nazarbayev University,
Astana, Kazakhstan
Email: *[email protected]; **[email protected]
Abstract
The complexes of transition metals with pincer type ligands are complexes that possess three
donor atoms positioned in meridional manner. The unique balance of stability vs reactivity for
pincer complexes is obtained due to its rigid nature and easily tunable steric and electronic
properties, which allows elegant enhancement of selectivity for catalytic reactions [1]. Huge
number of researchers is interested in chemistry of these complexes, particularly in activation
of C-X (X = O, H, N, C), O-H and N-H polar bonds. Whereas the complexes with ligands
having symmetrical side arms are extensively studied already, the complexes with
unsymmetrical ligands carrying different donors at side arms are investigated to notably less
extend and mainly focused on neutral or anionic ligands, possessing an anionic donor at central
position. In such cases, these ligands mainly act as “spectator” ligands. In contrast, pincer type
complexes with anionic ligands in side arm positions can behave as bifunctional catalysts [2].
Here we report the synthesis and coordination chemistry of unsymmetrical phosphinite POCN
pincer ligands produced from 3-hydroxybenzaldehyde by addition of imino and phosphinito
functional groups in a stepwise fashion. Coordination complexes of the synthesized ligands
with transition metals as Ir, Ni, Pd and Rh were investigated and applied in catalysis of
hydrosililation reactions. Two methods were used to introduce a metal into the ligand’s
framework A) Oxidative addition to the central C-H bond B) Ligand deprotonation in the
bridgehead C-H position and addition of the corresponding transition metal halide salts as
shown on the Scheme above.
Reference
1. Choi, J.; Macarthur, A. H. R.; Brookhart, M.; Goldman, A. S. Chem. Rev. 2011, 111(3), 1761–1779.
2. Spasyuk, D. M.; Zargarian, D. Inorg. Chem. 2010, 49(13), 6203–6213.