Titanium and zirconium complexes of the N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-butadiene ligand: syntheses, structures and uses in catalytic hydrosilylation reactionsElectronic supplementary information (ESI) available: X-ray crystallographic files for 2, 3 and 5-8 in CIF format and Table S1. CCDC 1011649-1011654. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt02013h

We report here a number of dianionic 1,4-diaza-1,3-butadiene complexes of titanium and zirconium synthesised by a salt metathesis reaction. The reaction of either CpTiCl 3 or Cp 2 TiCl 2 with the dilithium salt of N , N ′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene [ 1 ; abbreviated (Dipp) 2 DADLi 2 ] afforded the mono-cyclopentadienyl titanium complex [η 5 -CpTi((Dipp) 2 DAD)Cl] ( 2 ) bearing a dianionic ene-diamide ligand, while the analogous reaction of zirconocene dichloride (Cp 2 ZrCl 2 ) with the dilithium salt 1 gave the bis-cyclopentadienyl zirconium complex [Cp 2 Zr{(Dipp) 2 DAD}] ( 3 ). The metal dichloride complexes [Ti((Dipp) 2 DAD)Cl 2 ] ( 4 ) and [{(Dipp) 2 DADZrCl(μ-Cl)} 2 (κ 3 -Cl)(Li)(OEt 2 ) 2 ] ( 5 ) were obtained by the reaction of 1 and anhydrous metal tetrachloride in a 1 : 1 molar ratio in diethyl ether at room temperature. Meanwhile, the homoleptic titanium complex [Ti{((Dipp) 2 DAD)} 2 ] ( 6 ) was isolated in good yield by the treatment of 1 with TiCl 4 in a 1 : 2 molar ratio in diethyl ether. The complexes 2 and 5 were further reacted with neosilyl lithium to afford mono- and bis-alkyl complexes of titanium [η 5 -CpTi{(Dipp) 2 DAD}(CH 2 SiMe 3 )] ( 7 ) and zirconium [Zr{(Dipp) 2 DAD}(CH 2 SiMe 3 ) 2 ] ( 8 ) respectively. Molecular structures of the complexes 2 , 3 , and 5-8 in the solid states were confirmed by single crystal X-ray diffraction analysis. The solid state structures of all the complexes reveal that the metal ions are chelated through the amido-nitrogen atoms and the olefinic carbons of the [(Dipp) 2 DAD] 2− moiety, satisfying the σ 2 ,π coordination mode. Compound 8 was used as a catalyst for the intermolecular hydrosilylation reaction of a number of olefins, and moderate activity of catalyst 8 was observed. Various Ti and Zr complexes with Dipp 2 DAD ligand and their alkyl derivatives are obtained via salt metathesis reaction and catalytic hydrosilylation reactions by Zr alkyl complex are reported.