Synthesis and structures of complexes with axially chiral isoquinolinyl-naphtholate ligands

The synthesis of axially chiral ligands 1-(3',6'-di-t-butyl-2'-hydroxy-1'-naphthyl)-3-R-isoquinoline (R = H, Pr-i, Bu-t) (L-R-H) is described. Ligands with unsubstituted isoquinolinyl rings tend to give 1:2 metal complexes. The syntheses and crystal structures of Li-2(LH)(2)(THF)(2) (9), (L-H)(2)Ti(OPri)(2) (12), Zn(L-H)(2) (13) and [Mg(L-H)(2)](2) (14) are reported. Complex formation is highly stereoselective; the ligands in 1:2 complexes have the same stereochemistry (i.e. R,R and S,S but not R,S), whereas in the binuclear magnesium compound 14 the bridging and non-bridging ligands L-H have opposite stereochemistry. The reaction of L-H-H with Pd(acac)(2) afforded the N,O chelate Pd(acac)(L-H) (10), whereas towards K2PtCl4 the same ligand acts as an N-donor only, to give trans-PtCl2(L-H- H)(2) (11) in which the OH groups are hydrogen-bonded to one of the two chloride ligands. The more bulky ligand with a t-butyl substituent in the 3-position of the isoquinolinyl ring reacts with zinc and magnesium bis(amides) to give the mixed-ligand species (L-Bu)ZnN(SiMe3)(2) and (L-Bu)MgN(SiMe3)(2), respectively, which catalyse the ring-opening polymerisation of e-caprolactone (CL) and rac-lactide (LA).