Reaction of TiCl4 with the reagents RN(SiMe3)(2) in dichloromethane precipitates red to black powders (R = 1-adamantyl, phenyl. pentafluorophenyl, 3,5-bis(trifluoromethyl)phenyl), which on treatment with tetrahydrofuran gives the new THF adducts [Ti(NR)Cl(mu-Cl)(THF)(2)](2). The complexes are dimeric in the solid state with bridging chloride and terminal imido ligands. Activation with MAO (methylaluminoxane) gives ethene polymerisation catalysts with productivities of up to 31 kg PE [(mol complex) h bar](-1). (C) 2004 Elsevier Ltd. All rights reserved.