Synthesis and structures of tris(2-pyridyl)aluminate sandwich compounds [{RAl(2-py')2}2M] (py' = 2-pyridyl, M = Ca, Mn, Fe).

Reactions of the lithium salts [{RAl(2-py')3Li·THF] [2-py' = 2-py (2-pyridyl), R = (n)Bu (1), R = (sec)Bu (2); py' = 5-Me-2-py (5-methyl-2-pyridyl), R = Me (3); 6-Me-2-py (6-methyl-2-pyridyl), R = Et (4b)] with the corresponding metal(ii) halides give the new heterobimetallic sandwich compounds [{RAl(2-py)3}2M] [R = (n)Bu, M = Ca (5), Mn (6), Fe (7); R = (sec)Bu, M = Ca (8), Mn (9)], [{MeAl(5-Me-2-py)3}2Ca] (10) and [{EtAl(6-Me-2-py)3}2Ca] (11) and the co-complex [{EtAl(6-Me-2-py)3}Mn(μ-Cl)Li{(6-Me-2-py)3AlEt}] (12). While neither the bridgehead group (R) nor remote ring Me-groups have any impact on metal coordination in 5-10, the introduction of Me groups into the pyridyl substituent at the 6-position (i.e., adjacent to the donor pyridyl-N atoms) has a marked effect on the ability of the ligands to form sandwich arrangements, as seen in the distorted structure of the sandwich compound 11 and in the formation of the co-complex 12, consisting of a two half-sandwich arrangement linked by a μ-Cl ion. The syntheses and solid-state structures of the new precursor 4b and the new compounds 5-12 are reported.