Enantiomerically pure copper(I) and zinc(II) complexes of a novel C3-symmetric polypyrazole ligand

C3 Symmetry in Asymmetric Catalysis and Chiral Recognition

“…A Cu I complex of one of these ligands was shown to catalyze the cyclopropanation of styrene with diazoesters with up to 60 % ee. [75] The geometry around the metal ion heavily depends on the structure of the ligand: in the Tl I complex of the tris(pyrazolyl)hydroborate prepared from 28 b the torsion angles Tl-N-N-C are close to 1808, and the Tl I complex prepared from 28 c (X B) has a distorted propellerlike structure. [76] A little later three types of borate ± [Rh I LL] complexes (LL 2 CO, norbornadiene, cyclooctadiene) were identified.…”

The structures of chiral and racemate campho[2,3-c]pyrazole: A combined crystallographic, solid-state NMR and computational study

“…Campho [2,3-c]pyrazole (1) has been the subject of many studies: synthetic [4][5][6], structural [7], reactivity [3,[8][9][10][11][12], and as ligands in coordination chemistry [13][14][15][16][17][18][19]. The tautomerism has been studied proving that the proton is at the 2-position (2H-indazole) [7,20], a fact that has been related to the Mills-Nixon effect [21].…”

“…(4) and (5) identify molecules within each trimer. Calculations based on trimers improve the correlation but C3 and C7a continue to be the atoms with the largest residuals, probably because they are linked to 14 …”

C3-Symmetrie in der asymmetrischen Katalyse und der chiralen Erkennung

“…Ein Cu I -Komplex eines der letztgenannten Liganden katalysiert die Cyclopropanierung von Styrol durch Diazoester mit bis zu 60 % ee. [75] Eine interessante Beobachtung ist, daû die Geometrie um das Metallion stark von der Struktur des Liganden abhängt. Das belegen die Tl-N-N-C-Torsionswinkel in Tl I -Komplexen, die aus den Tris(pyrazolyl)hydroboraten 28 b und 28 c (X B) hergestellt wurden: Im ersten Fall liegt der Winkel nahe 1808, im zweiten dagegen hat der Komplex eine verzerrte, propellerähnliche Struktur.…”