Bis Amido Ligand Research Articles

A Structurally Rigid Bis(amido) Ligand Framework in Low-Coordinate Ni(I), Ni(II), and Ni(III) Analogues Provides Access to a Ni(III) Methyl Complex via Oxidative Addition

A structurally persistent bis-amido ligand framework capable of supporting nickel compounds in three different oxidation states has been identified. A highly unusual, isolable Ni(III) alkyl species has been prepared and characterized via a rare example of a two-electron oxidative addition of MeI to Ni(I).

Early and Late Transition Metal Complexes Stabilised by Imidazopyridazine‐Substituted Bisamido Ligands

AbstractThe preparation of a series of new imidazo[1,5‐b]pyridazine‐substituted diamines (5) is reported. They can be synthesised by the nucleophilic ring transformation of 2‐amino‐5‐methyl‐1,3,4‐oxadiazolium halogenides (1) with diaminoalkanes followed by condensation reactions with 1,3‐diketones. After deprotonation they were then used as bisamido ligands. These ligands stabilise early and late transition metal complexes as five‐membered chelates. The reaction with selected group 4 metals (titanium and zirconium) leads via amine elimination to unusual dark blue and purple mononuclear amido complexes. Deprotonation of the bisamido ligands using BuLi and further reaction with group 6 metals like chromium results in a dinuclear octahedral CrIII complex, where the different coordinated metal centres are bridged by two of the amido N atoms. The double deprotonation of 5 followed by reaction with the group 9 metals rhodium and iridium led to dinuclear complexes in a trans binding mode. The X‐ray structures of one of the novel bisamido ligands (protonated) and all complexes are reported and discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis and characterisation of novel zirconium(iv) derivatives containing the bis-amido ligand SiMe2(NRR′)2

The silicon compounds SiMe2(NRR′)2 [NRR′ = NMe2 (1), NEt2 (2), NC4H8 (3), NHEt (4), NHiPr (5), NHtBu (6), NMeBu (7)] have been synthesised via aminolysis of the dichloro species SiMe2Cl2 and their ligating ability has been investigated towards zirconium(IV). The dimer zirconium compound {Zr[(NiPr)2SiMe2]2}2 (8) has been synthesised by reacting ZrCl4 with the lithium salt Li2[(NiPr)2SiMe2] and its molecular structure has been determined in the solid state by X-ray diffraction analysis. The reaction of ZrCl4 with SiMe2(NRR′)2 yields the Lewis adducts ZrCl4[(NRR′)2SiMe2] [NRR′ = NMe2 (10), NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu (15)]. On the other hand, the mixed amido derivative Zr(NMe2)3(NHMe)[(NtBu)SiMe2(NHtBu)] (9) has been obtained from the reaction of Zr(NMe2)4 with SiMe2(NHtBu)2. The solution molecular structure and dynamics of the zirconium derivatives have been elucidated by 1D and 2D multinuclear NMR spectroscopy.

Synthesis, characterization and reactivity of amido titanium and zirconium complexes

The polymerization of ethylene and propylene was studied by using a series of mono- and spirocyclic coordinatively unsaturated early transition metal amides as pre-catalysts. Amino complexes were prepared either by metathesis reaction of Cp 2ZrCl 2 and the dilithium salt of the bisamido ligand (Me 3SiN(CH 2) 2NSiMe 3) 2−, by transamination reaction of Zr(NMe 2) 4 with two equivalents of the diamine ligand (Me 3SiNH(CH 2) 2NHSiMe 3), and by metathesis reaction of ZrCl 4 · 2THF or TiCl 4 with equimolar amounts of the dilithium salt (Me 3SiN(CH 2) 2NSiMe 3) 2. The complexes obtained were characterized by standard spectroscopic techniques. ‘Cationic’ polymerization catalysts were generated from the early transition-metal amides with methylalumoxane. Polymerization activity is dependent on catalyst and co-catalyst concentrations.

Amides Nonplanar Solely by CN Bond Rotation

Dunitz parametrization of the distortion of the bisamido ligands in the octahedrally coordinated Co-complex 1 indicated that the CN bond in both amide groups is strongly twisted (15 and 17°, resp.). Surprisingly, however, no pyramidalization takes place at the amide C and N atoms.