This invention is directed to new mono-cyclopentadienyl (“mono-Cp”) metallocene catalyst compounds useful for producing high viscosity PAOs with narrow molecular weight distribution and good shear stability. Specifically, this invention relates to a group of bridged mono-Cp catalysts wherein, in an embodiment of the invention, the aromatic ring structure is substituted with: 1) at least one phenyl group, 2) at least one alkyl group, and 3) at least one other group, such as a hydrocarbyl group, a heteroatom, or a heteroatom-containing group.