The interaction of ((MeSiBu)-Bu-t)(2)((NBuLi)-Bu-t)(2) with MCl4 in hot toluene produces {((MeSiNBu)-Bu-t)(2)((NBu)-Bu-t)(2)}MCl2, M = Zr (1), Hf (2), in good yields. The light-yellow and colorless solids are isostructural and crystallize in the monoclinic crystal system, space group P2(1)/n, with four molecules in the unit cell. The unit cell dimensions for 1 (293 K) are a = 9.174(6) Angstrom, b = 18.027(13) Angstrom, c = 16.515 Angstrom, beta = 98.81(6)degrees, and those for 2 (213 K) are a = 9.1871(1) Angstrom, b = 17.8553(2) Angstrom, c = 16.4770(3) Angstrom, beta = 99.339(1)degrees. The metal atoms are pseudotetrahedrally coordinated by cyclodisilazane and chloride ligands but have one additional weak bonding interaction with a cyclodisilazane ring-nitrogen atom. Treatment of 1 or 2 with 2 equiv of MeMgCl in ether affords the corresponding dimethyl species ({(MeSiNBu)-Bu-t)2((NBu)-Bu-t)(2)}MMe2, M = Zr (3), Hf(4). These isostructural, colorless organometallic compounds are remarkably stable to atmospheric oxygen and moisture. They crystallize in the monoclinic space group C2/c, Z = 4. The cell parameters for 3 (298 K) are a = 18.867(2) Angstrom, b = 9.361(1) Angstrom, c = 18.059(3) Angstrom, beta = 119.49-(1)degrees, and those for 4 (212 K) are a 18.8066(4) Angstrom, b = 9.3208(2) Angstrom, c = 17.8725(3) Angstrom, beta = 119.508(1)degrees. The dimethyl species are structurally very similar to the dichloro complexes 1 and 2, with the notable exception that the metal centers in these organometallic compounds are truly four-coordinate.