A high-temperature solution process for polymerizing ethylene is disclosed. The polymerization is performed in the presence of a preassembled bimetallic Ziegler-Natta catalyst and an aluminum compound. Molecular modeling calculations predict that the bimetallic Ziegler-Natta catalyst will have good activity and improved stability versus traditional Ziegler-Natta catalysts. This makes the catalyst especially suitable for solution polymerization processes, which require a thermally robust catalyst.