Supraphos: A supramolecular strategy to prepare bidentate ligands

Abstract

Herein, we report a new strategy for the preparation of chelating bidentate ligands, which involves the mixing of two mondentate ligands functionalized with complementary binding sites. The assembly process is based on selective metal-ligand interactions employing phosphite zinc(II) porphyrins 1-6 and the nitrogen-containing phosphorus ligands b-i (Scheme 1). Only 14 monodentate ligands were utilized to generate a library of 48 palladium catalysts based on supraphos-type bidentate ligands. The characterization of rhodium complexes based on representative Supramolecular bidentate ligands and the comparison of their performance in the hydroformylation of styrene will be presented. The current library of catalysts was tested in the asymmetric palladium-catalyzed alkylation of rac-1,3-diphenyl-2-propenyl acetate, which resulted in a large variety in the observed enantioselectivity for the different catalysts. Importantly, small variations in the supraphos building blocks, lead to large differences in the enantioselectivity imposed by the catalyst, the most selective catalyst producing 97% ee.

Synthesis, Characterization, and Crystal Structures of Tris(2-pyridyl)phosphine Sulfide and Selenide

“…Synthesis P(2-py) 3 was synthesized by the reaction of 2-lithiopyridine, prepared by the treatment of butyl lithium on 2-bromopyridine at -100 • C, with phosphorus trichloride at the same temperature (Scheme 1). 22…”

“…[8][9][10] The first preparation of pyridylphosphine was presented in 1944 by Davies and Mann as part of a study on the optical resolution of tertiary phosphines. 11 There has been an increasing usage of tris(2-pyridyl)phosphine, P(2-py) 3 , in inorganic and organometallic chemistry, primarily because of its interesting structural feature that retains both phosphorus and nitrogen atoms with versatile coordination possibility. There are four coordination modes found for complexes containing P(2-py) 3 , namely, phosphorus monodentate, 12,13 η 2 -P,Nchelate, 14,15 µ-P,N-bridge, 16 and η 3 -N, N , N -chelate.…”

“…11 There has been an increasing usage of tris(2-pyridyl)phosphine, P(2-py) 3 , in inorganic and organometallic chemistry, primarily because of its interesting structural feature that retains both phosphorus and nitrogen atoms with versatile coordination possibility. There are four coordination modes found for complexes containing P(2-py) 3 , namely, phosphorus monodentate, 12,13 η 2 -P,Nchelate, 14,15 µ-P,N-bridge, 16 and η 3 -N, N , N -chelate. 17 Thus, application of P(2-py) 3 ligations affords numerous novel and useful complexes.…”

“…There are four coordination modes found for complexes containing P(2-py) 3 , namely, phosphorus monodentate, 12,13 η 2 -P,Nchelate, 14,15 µ-P,N-bridge, 16 and η 3 -N, N , N -chelate. 17 Thus, application of P(2-py) 3 ligations affords numerous novel and useful complexes. [18][19][20] Apart from its characteristics in coordination chemistry, the catalysis aspects of P(2-py) 3 for the reactions employing triphenylphosphine have been recently explored.…”

“…17 Thus, application of P(2-py) 3 ligations affords numerous novel and useful complexes. [18][19][20] Apart from its characteristics in coordination chemistry, the catalysis aspects of P(2-py) 3 for the reactions employing triphenylphosphine have been recently explored. 21 In an effort to progress our knowledge about the relation between structure and properties, we have reported the synthesis and structure of tris(2-pyridyl)phosphine sulfide and selenide by single crystal X-ray analysis.…”