The zirconium and hafnium imido metalloporphyrin complexes (TTP)M=NAr(i(Pr)) (TTP = meso-5,10,15,20-tetra-p-tolylporphyrinato dianion; M = Zr (1), Hf; Ar(i(Pr)) = 2,6-diisopropylphenyl) were used to mediate addition reactions of carbonyl species and metathesis of nitroso compounds. The imido complexes react in a stepwise manner in the presence of 2 equiv of pinacolone to form the enediolate products (TTP)M[OC(1Bu)CHC(1Bu)(Me)O] (M = Zr (2), Hf (3)), with elimination of H2NAr(i(Pr)). The bis(μ-oxo) complex [(TTP)ZrO]2 (4) is formed upon reaction of (TTP)Zr=NAr(i(Pr)) with PhNO. Treatment of compound 4 with water or treatment of compound 2 with acetone produced the (μ-oxo)bis(μ-hydroxo)-bridged dimer [(TTP)Zr]2(μ-O)(μ-OH)2 (5). Compounds 2, 4, and 5 were structurally characterized by single-crystal X-ray diffraction.