New Insights into Cinchonine–Aluminium Complexes and Their Application as Chiral Building Blocks: Unprecedented Ligand‐Exchange Processes in the Presence of ZnR2 Compounds

Previous studies have demonstrated that [(CN)₂AlCl] and [R₂Al(μ‐CN)]₂ (CN=deprotonated cinchonine) complexes can effectively act as chiral, semirigid, N,N‐ditopic metalloligands for Zn‐containing nodes, and provide viable means for constructing new, homochiral, heterometallic, coordination polymers of zigzag and helical topologies. These findings have prompted further investigations on the organometallic analogues of the formula [(CN)₂AlR], anticipating their utility as N,N‐metalloligands for ZnR₂ units. Surprisingly, reactions of [(CN)₂AlMe]‐type metalloligands with ZnR₂ compounds (R=Me or Et) revealed unprecedented ligand‐exchange processes, including zinc‐to‐aluminium and aluminium‐to‐zinc transmetalations of alkyl groups. The molecular and crystal structure of the resulting compounds was determined by X‐ray diffraction analysis. From the reaction of [(CN)₂AlMe] with ZnMe₂ a new pseudopolymorphic form of a noncovalent porous material based on [Me₂Al(μ‐CN)]₂ molecules was isolated. Strikingly, the analogous reaction involving ZnEt₂ led to the generation of a new chiral 4N‐tetratopic heterometalloligand [(CN)EtAl(μ‐CN)₂ZnEt]. The latter unit was successfully connected by alkyl‐exchanged ZnMe₂ nodes to give an original homochiral heterometallic {[(CN)EtAl(μ‐CN)₂ZnEt]ZnMe₂}_n coordination polymer adopting a snake 1D motif. The outcome of the revealed reactions indicates the complicated multistep reaction route that involves redistribution of cinchonine and alkyl ligands among the Al and Zn centers, and a general reaction scheme is proposed. The results are in strong contrast with the previously studied inorganic–organic [(CN)₂AlCl/ZnCl₂] system, which exclusively affords a helical coordination polymer based on ZnCl₂ nodes and (CN)₂AlCl metalloligands and lacks the exchange of CN ligands.