Synthesis of Intramolecularly Coordinated Aluminum and Gallium Compounds for the Preparation of [1]Ferrocenophanes

Two different ligands equipped with pyridine donor moieties, (2-H4C5N)(Me3Si)2C (R′) and (2-H4C5N)(Me3Si)(Me)C (R″), were applied in the preparation of aluminum and gallium dihalides that could be employed in salt metathesis reactions with 1,1′-dilithioferrocene. R′GaCl2 (1) was accessible from LiR′ and GaCl3 (21%), whereas the respective aluminum compound R′AlCl2 (3Cl) and its bromine analogue R′AlBr2 (3Br) could only be prepared through the intermediate species R′AlMe2 (2) by the addition of Me3SnCl and Br2, respectively. An improved synthesis of the ligand precursor R″H, (2-H4C5N)(Me3Si)(Me)CH), is described. Attempted syntheses of R″AlX2 starting from LiR″ and AlCl3 or ClAlMe2 gave the bis-ligand compounds R″2AlCl (4) and R″2AlMe (6), respectively. As deduced from proton NMR spectroscopy, the formation of 6 proceeded through the intermediate R″AlMe2 (5) and was facilitated in the presence of tmeda. The formation of 4 and 6, respectively, is diastereospecific, as only rac isomers were formed (R,R-Λ and...