The reaction of 4 equiv of LiNHAr (Ar = 2,6-06 3' 2) with a solution of ZrCl4(THF)2 in THF/pyridine yields Zr(=NAr)(NHAr)2(py)2 (1) in high yield. Zr(=NAr)(NHAr)2(py)2 reacts with 1 and 2 equiv of Me3SiCl in THF/pyridine to provide Zr(=NAr)(NHAr)Cl(py)2 (2) and Zr(=NAr)Cl2(py)3 (3), respectively. ZrCl4(THF)2 reacts with 4 equiv of LiNHAr, followed by 2 equiv of Me3SiCl (in THF), to afford Zr(=NAr)Cl2(THF)2 (4) in a high-yield, one-pot synthesis. Hf(=NAr)Cl2(THF)2 ( 5) is prepared similarly. Zr(=NAr)(NHAr)Cl(py)2 reacts with 1 equiv of K[N(SiMe3)2] in THF to provide Zr(=NAr)(NHAr) [N(SiMe3)2] (py)2 (6), which could not be converted into a bis(imido) species. Both Hf(=NAr)Cl2(THF)2 and Zr(=NAr)Cl2(THF)2 react with K2(C8H8) to provide [(?/8-C8H8)Zr(=NAr)]2 (7) and [(?;8-C8H8)Hf(=NAr)]2 (8) in high yield. Zr(=NAr)Cl2(THF)2 reacts with 1 equiv of Li(C3H4Me) in THF to provide [(r/5-C5H4Me)Zr(=NAr)Cl]2 (9) in moderate yield. An X-ray structural determination of this compound reveals a dimeric structure with bridging imido ligands. [(tj5-C5H4-

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Alkylation of tantalum(III) arene complexes affords stable dialkyl and monoalkyl halide species ( 6-C6Me6)Ta(DIPP)R2 (DIPP = 2,6-diisopropylphenoxkte) and (776-C6Mee)Ta(DI PP)RX. The alkyl hydride complexes (776-C6Me6)Ta(D I PP)R(H) are also prepared from { 6-C6Me6)Ta(DIPP)RX and UBEt3H. The arene ring in ( 6-C6Me6)Ta(DIPP)Et2 exhibits a structure consistent with a diene-diyl distortion. The first evidence for the formation of a d1 arene species is presented in cyclic voltammetry experiments on these compounds.