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Trimethylphosphine halide complexes of titanium, zirconium and hafnium in oxidation states IV, III and II. Crystal structure of MI 4 (PMe 3 ) n (M = Zr, n = 3; M = Hf, n = 2.5), M 2 X 6 (PMe 3 ) 4 (M = Hf, Ti, X = I; M = Zr, X = Br) and (μ-η 6 ,η 6 -C 6 H 6 )Hf 2 I 4 (PMe 3 ) 4 C 6 H 6
The reaction of MI 4 (M = Zr, Hf) with trimethylphosphine in benzene solution leads to different compounds, ZrI 4 (PMe 3 ) 3 (1) and HfI 4 (PMe 3 ) 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 three P atoms. Superposition of two molecules, HfI 4 (PMe 3 ) 3 and HfI 4 (PMe 3 ) 2 in 1:1 ratio has been found in 2. The reduction of MX 4 with 1 equiv. of Na/Hg amalgam in the presence of PMe 3 afforded bioctahedral M(III) complexes Hf 2 I 6 (PMe 3 ) 4 (3), Zr 2 Br 6 (PMe 3 ) 4 (4) and Ti 2 I 6 (PMe 3 ) 4 (5). The compounds 3 and 4 are characterized by a cis-cis arrangement of phosphine ligands with respect to two M centres with direct M M bonds at distances of 3.33 9 (3) and 3.20 9 (4). There is no Ti-Ti bond in the cis-trans complex 5 with the Ti Ti distance of 4.30 9. The reduction of HfI 4 with 2 equiv. of Na/Hg amalgam in the presence of PMe 3 resulted in the isolation of Hf(II) complex, (μ-η 6 ,η 6 -C 6 H 6 )Hf 2 I 4 (PMe 3 ) 4 C 6 H 6 (6). The complex 6 contains dinuclear molecules with two-sided coordination of benzene by two Hf atoms. The strong deformation of coordinated benzene in the form of a twisted boat (C-C 1.45-1.46 9) is explained by steric repulsion from the neighbouring PMe 3 ligands.