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Synthesis and Characterization of a Family of POCOP Pincer Complexes with Nickel: Reactivity Towards CO 2 and Phenylacetylene
Author(s) -
Jonasson Klara J.,
Wendt Ola F.
Publication year - 2014
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/chem.201403246
Subject(s) - pincer movement , chemistry , medicinal chemistry , pincer ligand , phenylacetylene , reactivity (psychology) , hydride , ligand (biochemistry) , phosphine , nickel , bromide , oxidative addition , stereochemistry , metal , inorganic chemistry , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology , catalysis
A cyclohexyl‐based POC sp 3OP pincer ligand (POC sp 3OP= cis ‐1,3‐bis(di‐ tert ‐butylphosphinito)cyclohexyl) cyclometalates with nickel to generate a series of new POC sp 3OP‐supported Ni II complexes, including the halide, hydride, methyl, and phenyl species. trans ‐[NiCl{ cis ‐1,3‐bis(di‐ tert ‐butylphosphinito)cyclohexane}], [(POC sp 3OP)NiCl] ( 1 a ) and the analogous bromide complex ( 1 b ) were synthesized and fully characterized by NMR spectroscopy and X‐ray crystallography. Cyclic voltammetry measurements of 1 a and 1 b alongside their bis(phosphine) analogues [(PC sp 3P)NiCl] ( 2 a ) and [(PC sp 3P)NiCl] ( 2 a ) (PC sp 3P= cis ‐1,3‐bis(di‐ tert ‐butylphosphino)cyclohexyl) indicate a reduced electron density at the metal center upon introducing electron‐withdrawing oxygen atoms in the pincer arms. The methyl [(POC sp 3OP)NiMe] ( 3 ) and phenyl [(POC sp 3OP)NiPh] ( 4 ) complexes were formed from 1 a by reaction with the corresponding organolithium reagents. 1 a also reacts with LiAlH 4 to give the hydride complex [(POC sp 3OP)NiH] ( 5 ). The methyl complex 3 reacts with phenyl acetylene to give the acetylide complex [(POC sp 3OP)NiCCPh] ( 6 ). The reactivity of compounds 3 – 5 towards CO 2 was studied. The hydride complex 5 and the methyl complex 3 both underwent CO 2 insertion to form the formate species [(POC sp 3OP)NiOCOH] ( 7 ) and acetate species [(POC sp 3OP)NiOCOCH 3 ] ( 8 ), respectively, although with a higher barrier of insertion in the latter case. Compound 4 was unreactive towards CO 2 even at elevated temperatures. Complexes 3 – 8 were all characterized by NMR spectroscopy and X‐ray crystallography.