The syntheses of several cobalt diglyoximate complexes connected by one or two aluminum bridges are described. The aluminum centers are supported by tunable tetradentate diamine bisphenoxide ligands. Electrochemical investigations revealed that the number of aluminum bridges and the nature of the substituents on the phenoxide ligands significantly affect the cobalt reduction potentials. The present aluminum–cobalt compounds are electrocatalysts for proton reduction to hydrogen at potentials negative relative to those of the boron- and proton-bridged analogs. The reported synthetic strategies allow modulation of the reduction potentials and the secondary coordination sphere interactions by tuning the ancillary ligands bound to aluminum.