The preparation and structural characterization of a series of group 4 complexes supported by 2,2'-phenylphosphinobis(4,6-di-tert-butylphenolate) ([OPO](2-)) are described. The reaction of either H-2[OPO] with Ti(OR)(4) (R = Et, Pr-i) or Li-2[OPO] with TiCl4(THF)(2) produced yellowish-orange crystals of Ti[OPO](2), regardless of the stoichiometry of the starting materials employed. Comproportionation of the bis-ligand complex Ti[OPO](2) with 1 equiv of TiCl4(THF)(2) led to the formation of [OPO]TiCl2(THF) as brownish-red crystals. Surprisingly, treatment of H-2[OPO] with [(Me3Si)(2)N](2)MCl2 (M = Zr, Hf), irrespective of the molar ratio, generated colorless crystals of the corresponding bis-ligand complex [OPO](2)M(OH2) as an aqua adduct. The solution and solid-state structures of these group 4 complexes were all characterized by multinuclear NMR spectroscopy and X-ray crystallography, respectively.