Condensation of phthalodinitrile and 2-amino-5,6,7,8-tetrahydroquinoline gave the bis(2-pyridylimino)isoindole protioligand 1 (thqbpiH) in high yield. Deprotonation of thqbpiH (1) using LDA in THF at -78 °C yields the corresponding lithium complex [Li(THF)(thqbpi)] (2) in which the lithium atom enforces almost planar arrangement of the tridentate ligand, with an additional molecule of THF coordinated to Li. Reaction of cobalt(II) chloride or iron(II) chloride with one equivalent of the lithium complex 2 in THF led to formation of the metal complexes [CoCl(THF)(thqbpi)] (3a) and [FeCl(THF)(thqbpi)] (3b). The paramagnetic susceptibility of 3a,b in solution was measured by the Evans method (3a: μ(eff) = 4.17 μ(B); 3b: μ(eff) = 5.57 μ(B)). Stirring a solution of 1 and cobalt(II) acetate tetrahydrate in methanol yielded the cobalt(II) complex 4 which was also accessible by treatment of 3a with one equivalent of silver or thallium acetate in DMSO. Whereas 3a,b were found to be mononuclear in the solid state, the acetate complex 4 was found to be dinuclear, the two metal centres being linked by an almost symmetrically bridging acetate. For all transition metal complexes paramagnetic (1)H as well as (13)C NMR spectra were recorded at variable temperatures. The complete assignment of the paramagnetic NMR spectra was achieved by computation of the spin densities within the complexes using DFT. The proton NMR spectra of 3a and 3b displayed dynamic behaviour. This was attributed to the exchange of coordinating solvent molecules by an associative mechanism which was analysed using lineshape analysis (ΔS(≠)= -154 ± 25 J mol(-1) K(-1) for 3a and ΔS(≠) = -168 ± 15 J mol(-1) K(-1) for 3b).

The synthesis of a new family of chiral tridentate monoanionic NNN-pincer ligands based on the 1,3-bis(2-pyridylimino)isoindoline (BPI) framework is reported. Ligands with substituents of varying steric demand were prepared starting from achiral and low priced materials. A kinetic enzymatic resolution was used as a key step for the preparation of enantiomerically pure ligands. In this way, both enantiomers of a given ligand could be produced enantioselectively (>99.5% ee). The corresponding cobalt alkyl complexes were obtained using a pyridine alkyl cobalt precursor complex and were applied in asymmetric hydrosilylation of several prochiral alkylaryl ketones with high yields (up to 100%) and enantioselectivity (up to 91% ee) to give the chiral alcohols after hydrolysis.

Since the first report in the early 1950s, 1,3‐bis(2‐pyridylimino)isoindolines (BPIs) have found widespread applications in organic, inorganic and materials chemistry. This microreview focuses on recent progress towards chiral BPI derivatives as ligands for enantioselective catalysis as well as developments in the use of BPI complexes in materials science, focusing on luminescent and birefringent materials.

Iron(II) and cobalt(II) alkyl complexes using tridentate bis(pyridylimino)isoindolates as ancillary ligands have been synthesized from the pyridine alkyl precursor complexes [(py) 2 Fe(CH 2 SiMe 3 ) 2 ] and [(py) 2 Co-(CH 2 SiMe 3 ) 2 ]. The extremely air-and moisture-sensitive compounds were structurally characterized in the solid state by X-ray diffraction as well as in solution by paramagnetic NMR spectroscopy. It is demonstrated that the paramagnetic shifts in the 13 C NMR spectra are dominated by strong Fermicontact interactions. All 13 C NMR signals can be assigned by correlation with DFT-calculated spin-density distributions.

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