The synthesis and characterization of several 2,9‐diarylphenanthrolines with anthracenyl substituents in the 2‐position is described. These compounds were used to prepare a series of homoleptic and heteroleptic bis(phenanthroline)copper(I) complexes, whose cyclic voltammetry, UV/Vis and fluorescence data are investigated. From PM3 semiempirical calculations it becomes clear that two different strategies can be applied to prepare clean heteroleptic complexes.

Modern organic synthesis (e.g., of natural products) is virtually impossible without employment of enantiomerically enriched compounds. In many cases, alkyllithium compounds are key intermediates for the generation of these stereogenic substances. In recent years, the lithiated carbon atom in silicon-substituted benzyllithium compounds has become a focus of interest because it is possible to maintain its stereogenic information. Starting from a highly enantiomerically enriched benzylsilane, (R,S)-2 x quinuclidine could be obtained, and the absolute configuration at the metalated carbon atom was determined by X-ray diffraction analysis. In solution, a quartet was found in the (13)C NMR spectrum for the metalated carbon atom because of coupling between carbon and lithium, indicating a fixed lithium carbon contact at room temperature. After reaction of (R,S)-2 x quinuclidine with trimethylchlorostannane, the trapped product (S,S)-4 was obtained with a dr > or = 98:2 with inversion of the configuration at the metalated carbon. Multipole refinement against high-resolution diffraction data and subsequent topological analysis of the benchmark system (R,S)-2 x quinuclidine provide insight in the electronic situation and thus the observed stereochemical course of the transformations. Surprisingly, the negative charge generated at the carbanion hardly couples into the phenyl ring. The neighboring silicon atom counterbalances this charge by a pronounced positive charge. Therefore, the alpha-effect of the silicon atom is caused not just by a polarization of the electron density but also by an electrostatic bond reinforcement. Furthermore, the experimentally determined electrostatic potential unequivocally explains the observed back side attack of an electrophile under inversion of the stereogenic center with high diastereomeric ratios.

The crystal structures of aggregates between MeLi and PhLi and a (+)-sparteine surrogate ((+)-2) have been determined. The MeLi adduct 4 reveals a 2:2 dimer, while the PhLi adduct 6 forms a rare example of a 4:2 ladder structure, each capped by two of the diamine ligands. The observation that (+)-2 is equally effective as (-)-sparteine in s-BuLi-mediated asymmetric deprotonations, but leading to the opposite sense of stereoselectivity, is explained on the basis of the crystal structures and a computational study. Moreover, the crystal structure of the 2;2 dimer between MeLi and (-)-sparteine has been redetermined with advanced accuracy.

The crystal structures of the two chiral alkyllithium bases [n-BuLi.(-)-sparteine]2 (1) and [Et2O.(i-PrLi)2.(-)-sparteine] (2) have been determined. For compound 1, a symmetric dimer is observed in the solid state, with two (-)-sparteine ligands coordinating to the lithium centers. Because of steric reasons, compound 2 crystallizes as an unsymmetric dimer with the four methyl groups pointing away from the sterically demanding (-)-sparteine ligand. Compound 2 contains one four-coordinate lithium center [coordinated to (-)-sparteine] and one three-coordinate lithium center (coordinated to Et2O). As a result of this arrangement, significantly different Li-C distances are found in the central four-membered ring of compound 2.