Syntheses and complexes of new chiral heterocyclic ligands

Abstract

The complexation properties of the chiral heterocyclic ligand (4S,7R)- 7,8,8-trimethyl-4,5,6,7-tetrahydro-4,7-methano-1H(2H)-indazole (4) have been investigated and its site of coordination to transition metal ions has been established by n.m.r. spectroscopy and X-ray crystallography as occurring through the more hindered N1 nitrogen. N1, N2 and C3 substituted derivatives of 4 have been synthesised and characterised. These new compounds represent a diverse range of new chiral heterocyclic bidentate, tridentate and binucleating ligands. In total sixty two new ligands have been synthesised of which fifty are chiral. The complexation properties of the majority of these new ligands have been investigated. The structures of the following complexes have been determined by X-ray crystallography: [Cu(4)₂Cl₂] viz (8), a 4-coordinate copper complex with distorted tetrahedral geometry; [Pd(10)₂Cl₂] viz (11), a trans-dichloro palladium complex; [Pd(1 0)Cl]₂ viz (12), a chiral cyclopalladated complex; [Pd(28)Cl₂] viz (30), a cis-dichloro palladium complex; [Ni(33)₂(ClO₄)]ClO₄.EtOH viz (34), an octahedral nickel complex with a chelating bidentate perchlorate; [Pd(38)Cl₂] viz (39), a cis dichloro palladium complex; [Pd₂(42)₂Cl₄] viz (44), a chloro-bridged dimeric palladium complex; [Ni(61)₂](ClO₄)₂ viz (74) , an octahedral nickel complex and [Cu(71 )(NCS)₂] viz (75) , a five coordinate copper complex. The potential application of these new compounds in asymmetric catalysis is discussed.