Molecular structures of tris(1‐ tert ‐butyl‐2‐mercaptoimidazolyl)hydroborate complexes of titanium, zirconium and hafnium

Cyclopentadienyl and tris(pyrazolyl)hydroborate have found much use as supporting ligands in the chemistry of titanium, zirconium and hafnium, especially with respect to applications involving olefin polymerization catalysis. In contrast, closely related tris(1‐alkyl‐2‐mercaptoimidazolyl)hydroborate, [Tm R ], ligands have so far found little application to the chemistry of these elements, despite the fact that such ligands are currently used extensively in coordination chemistry. In view of the fact that a substituent in the 2‐position exerts a direct influence on the steric environment of the metal center, we report here the application of the sterically demanding tris(1‐ tert ‐butyl‐2‐mercaptoimidazolyl)hydroborate [Tm] ligand to these metals. Dichlorido(η 5 ‐cyclopentadienyl)[tris(1‐ tert ‐butyl‐2‐sulfanylidene‐2,3‐dihydro‐1 H ‐imidazol‐3‐yl)borato‐κ 3 S , S ′, H ]zirconium(IV) benzene hemisolvate, [Zr(C 21 H 34 BN 6 S 3 )(C 5 H 5 )Cl 2 ]·0.5C 6 H 6 , (I), dichlorido(η 5 ‐cyclopentadienyl)[tris(1‐ tert ‐butyl‐2‐sulfanylidene‐2,3‐dihydro‐1 H ‐imidazol‐3‐yl)borato‐κ 3 S , S ′, H ]titanium(IV) benzene hemisolvate, [Ti(C 21 H 34 BN 6 S 3 )(C 5 H 5 )Cl 2 ]·0.5C 6 H 6 , (II), [bis(1‐ tert ‐butyl‐2‐sulfanylidene‐2,3‐dihydro‐1 H ‐imidazol‐3‐yl)borato‐κ 3 S , S ′, H ]dichlorido(η 5 ‐cyclopentadienyl)zirconium(IV), [Zr(C 14 H 24 BN 4 S 2 )(C 5 H 5 )Cl 2 ], (III), (1‐ tert ‐butyl‐2,3‐dihydro‐1 H ‐imidazole‐2‐thione‐κ S )(1‐ tert ‐butyl‐2‐sulfanylidene‐1 H ‐imidazol‐3‐ido‐κ 2 N 3 , S )dichlorido(η 5 ‐cyclopentadienyl)zirconium(IV) benzene monosolvate, [Zr(C 7 H 11 N 2 S)(C 7 H 12 N 2 S)(C 5 H 5 )Cl 2 ]·C 6 H 6 , (IV), and tribenzyl[tris(1‐ tert ‐butyl‐2‐sulfanylidene‐2,3‐dihydro‐1 H ‐imidazol‐3‐yl)borato‐κ 3 S , S ′, S ′′]hafnium(IV) benzene tetrasolvate, [Hf(C 7 H 7 ) 3 (C 21 H 34 BN 6 S 3 )]·4C 6 H 6 , (V), have been structurally characterized by X‐ray diffraction. The [Tm] ligand coordinates to Ti and Zr in Cp[κ 3 S 2 , H ‐Tm]MCl 2 [M = Zr, (I), and Ti, (II)] in a κ 3 S 2 , H mode, while the benzyl compounds [Tm]M(CH 2 Ph) 3 [M = Zr and Hf, (V)] exhibit κ 3 S 3 coordination.