Catalyst systems useful for olefin polymerization are disclosed. The catalysts include a bimetallic complex that incorporates two linked indenoindolyl groups, each of which is pi-bonded through its cyclopentadienyl ring to one of the metals. Compared with conventional indenoindolyl complexes, the bimetallic complexes of the invention have enhanced ability to give polyolefins with desirably low melt indices. Certain bimetallic indenoindolyl complexes also provide a way to broaden polymer molecular weight distribution and thereby improve processability simply by regulating the amounts of comonomer and activator used in the polymerization.