Titanium and zirconium complexes of the N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-butadiene ligand: syntheses, structures and uses in catalytic hydrosilylation reactions

Abstract

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 CpTiCl3 or Cp2TiCl2 with the dilithium salt of N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene [; abbreviated (Dipp)2DADLi2] afforded the mono-cyclopentadienyl titanium complex [η(5)-CpTi((Dipp)2DAD)Cl] () bearing a dianionic ene-diamide ligand, while the analogous reaction of zirconocene dichloride (Cp2ZrCl2) with the dilithium salt gave the bis-cyclopentadienyl zirconium complex [Cp2Zr{(Dipp)2DAD}] (). The metal dichloride complexes [Ti((Dipp)2DAD)Cl2] () and [{(Dipp)2DADZrCl(μ-Cl)}2(κ(3)-Cl)(Li)(OEt2)2] () were obtained by the reaction of and anhydrous metal tetrachloride in a 1 : 1 molar ratio in diethyl ether at room temperature. Meanwhile, the homoleptic titanium complex [Ti{((Dipp)2DAD)}2] () was isolated in good yield by the treatment of with TiCl4 in a 1 : 2 molar ratio in diethyl ether. The complexes and were further reacted with neosilyl lithium to afford mono- and bis-alkyl complexes of titanium [η(5)-CpTi{(Dipp)2DAD}(CH2SiMe3)] () and zirconium [Zr{(Dipp)2DAD}(CH2SiMe3)2] () respectively. Molecular structures of the complexes , , and 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)2DAD](2-) moiety, satisfying the σ(2),π coordination mode. Compound was used as a catalyst for the intermolecular hydrosilylation reaction of a number of olefins, and moderate activity of catalyst was observed.

Balance between Metal and Ligand Reduction in Diiminepyridine Complexes of Ti

“…The authors do not appear to have considered the possible noninnocence of the DIP ligand in these formally Ti­(III) and Ti­(II) complexes. In contrast, recent work by the group of Panda on Ti complexes of the potentially redox active α-diimine (ADI) ligand indicates that in (ADI)­TiCl 2 , (ADI)­Ti­(Cp)­Cl, and (ADI)­Ti­(Cp)­CH 2 SiMe 3 the σ 2 ,π-bound ADI ligand is in the doubly reduced state. In the present work, we report the synthesis and characterization of ( Et DIP)Ti halide and alkyl complexes and probe the spectroscopic oxidation state of the metal using NMR, EPR, XRD, XPS, and computational methods.…”

Four‐ and Five‐Coordinate Titanium(IV) Complexes Supported by the dpp‐bian Ligand in ROP of L‐Lactide

“…The Ti atoms in 2 and 3 are, respectively, 1.2729(3) Å and 1.1914(9) Å away from the bisamidoacenaphthylene plane that is caused by π‐type interaction between the C=C fragment and the metal center . The observed values are slightly higher than those in the starting complex 1 (1.0576(3) Å) as well as in the similar alkoxide (dpp‐bian)Ti(O t Bu) 2 (1.1665(3) Å) …”

“…The Ti atoms in 2 and 3 are, respectively, 1.2729(3) Å and 1.1914(9) Å away from the bisamidoacenaphthylene plane that is caused by π-type interaction between the C=C fragment and the metal center. [20] The observed values are slightly higher than those in the starting complex 1 (1.0576(3) Å) as well as in the similar alkoxide (dpp-bian)Ti(OtBu) 2 (1.1665(3) Å). [9] By contrast, the titanium atom in 4 ( Figure 5), which has a square pyramidal environment (τ 5 = 0.07), is nearly in the ligand plane (0.2737(5) Å away), which points to a considerable decrease of π-d interaction.…”

Electronic and Geometric Structures of Paramagnetic Diazadiene Complexes of Lithium and Sodium

“…The list of stable DAD complexes encompasses main‐group metals, early and late transition metals, as well as the lanthanides and actinides . Important practical applications of metal diazadiene complexes include homogeneous catalysis, C−H bond activation, materials science, and the synthesis of single‐molecule magnets . A unique electronic property of 1,4‐diaza‐1,3‐dienes is that they are redox non‐innocent and can undergo one‐ and two‐electron reduction steps to afford the corresponding radical anions and the enediamide dianions, respectively, as shown in Scheme …”

“…This electronic flexibility in addition to the possibility of tuning the steric properties of DADs by using various substituents at both the C and N atoms account for the high versatility of DAD ligands in coordination chemistry. Scheme shows the different coordination modes of DAD ligands that have been reported in the literature …”