TRIMETHYLPHOSPHINE HALIDE-COMPLEXES OF TITANIUM, ZIRCONIUM AND HAFNIUM IN OXIDATION-STATE-IV, OXIDATION-STATE-III AND OXIDATION-STATE-II - CRYSTAL-STRUCTURE OF MI4(PME3)(N) (M=ZR, N=3 M=HF, N=2.5), M2X6(PME3)(4) (M=HF, TI, X=1 M=ZR, X=BR) AND -ETA(6),ETA(6)-C6H6)HF2I4-(PME3)(4)CENTER-DOT-C6H6

The reaction of MI4 (M=Zr, Hf) with trimethylphosphine in benzene solu tion leads to different compounds. ZrI4(PMe3)(3) (1) and Hfl(4)(PMe3)( 2.5) (2). According to the single-crystal X-ray diffraction study, Zr in 1 has a capped trigonal antiprismatic coordination by four I and th ree P atoms. Superposition of two molecules, HfI4(PMe3)(3) and Hfl(4)( PMe3)(2) in 1:1 ratio has been found in 2. The reduction of MX4 with 1 equiv. of Na/Hg amalgam in the presence of PMe3 afforded bioctahedral Mi (III) complexes Hf2I6(PMe3)(4) (3), Zr2Br6(PhMe3)(4) (4) and Ti2I6 (PMe3)(4) (5). The compounds 3 and 4 are characterized by a cis-cis ar rangement of phosphine ligands with respect to two M centres with dire ct M..M bonds at distances of 3.33 Angstrom (3) and 3.20 Angstrom (4). There is no Ti-Ti bond in the cis-trans complex 5 with the Ti...Ti di stance of 4.30 Angstrom. The reduction of HfI4 with 2 equiv. of Na/Hg amalgam in the presence of PMe3 resulted in the isolation of Hf(II) co mplex, (mu-eta(6),eta(6)-C6H6)Hf2I4(PMe3)(4) . C6H6 (6). The complex 6 contains dinuclear molecules with two-sided coordination of benzene b y two Hf atoms. The strong deformation of coordinated benzene in the f orm of a twisted boat (C-C 1.45-1.46 Angstrom) is explained by steric repulsion from the neighbouring PMe3 ligands. (C) 1998 Elsevier Scienc e S.A.