Half-sandwich titanium and zirconium complexes with tridentate dianionic aryloxide or arylsulfide ligands [R-2-{(2-XC6H4)NCH}C6H2O]2- ([XNOR]2-, R = H, X = O (L1); R = 4-Me-6-Bu t (R‘), X = O (L2); R = H, X = S (L3); R = 4-Me-6-Bu t (R‘), X = S (L4)) have been prepared. Reactions of CpMCl3 (M = Ti, Zr) with sodium salts of the aryloxide or arylsulfide ligands (L1−L4) afford CpTi[XNOR]Cl [R = H, X = O (1); R = 4-Me-6-Bu t (R‘), X = O (2); R = H, X = S (3); R = 4-Me-6-Bu t (R‘), X = S (4)] and CpZr[ONOR]Cl [R = H (5)], respectively. Complexes 1−5 were characterized by IR and 1H NMR spectra and elemental analyses, and their molecular structures have been determined by X-ray diffraction methods. The coordination properties of these complexes have been investigated in the solid state and compared to related systems. When activated by excess methylaluminoxane (MAO), these complexes can be used as catalysts for ethylene polymerization and exhibited moderate activities. The activities of arylsulfide complexes 3 and 4 are higher than those of their analogues, aryloxide complexes 1 and 2, and zirconium complex 5 is much more active than titanium complexes 1−4.