Zirconium Amide, Halide, and Alkyl Complexes Supported by Tripodal Amido Ligands Derived fromcis,cis-1,3,5-Triaminocyclohexane

Abstract

Zirconium complexes containing the chelating triamido ligands [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ] 3and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 } 3are reported. The dimethylamido complexes [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrNMe 2 (NHMe 2 ) (3) and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 }-ZrNMe 2 (NHMe 2 ) (4) were prepared from Zr(NMe 2 ) 4 and cis,cis-1,3,5-(C 6 F 5 NH) 3 C 6 H 9 (1) or cis, 3, ) 2 C 6 H 3 NH] 3 C 6 H 9 (2), respectively. As determined by X-ray crystallography, an ortho fluorine atom in the triamido ligand of complex 3 is coordinated to the zirconium center. The zirconium chloride complexes [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCl (5) and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 }ZrCl(THF) 2 (6) were prepared from Np 3 ZrCl and 1 or 2, respectively. Compound 5 reacts with MeMgBr, LiCH(SiMe 3 ) 2 , LiCH 2 SiMe 3 , and PhCH 2 -MgCl to give the corresponding alkyl derivatives [cis,cis-1,3,5-( 8), [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCH 2 SiMe 3 (9), and [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCH 2 Ph ( 10). An X-ray crystallographic study of 8 reveals the presence of an R-agostic interaction, as well as the coordination of two ortho fluorines to the metal center. These interactions persist in solution, as indicated by NMR studies. Compound 6 reacts with MeMgCl and LiCH(SiMe 3 ) 2 to give the corresponding alkyl derivatives {cis,- 12). The methyl derivative 7 reacts with 3 equiv of xylyl isocyanide to yield [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]Zr{N(2,6-Me 2 C 6 H 3 )dCMeC[dCdN(2,6-Me 2 C 6 H 3 )]N(2,6-Me 2 C 6 H 3 )} (15), which was structurally characterized. Complex 15 features three molecules of xylyl isocyanide that have been coupled to give a diazazirconacycle with an exocyclic ketenimine group. The alkyl derivatives 7-12 react with hydrogen at elevated temperatures to yield ZrF species derived from the activation of the fluorinated substituents on the triamido ligands, presumably via reactive hydride intermediates.

Reactivity of a functionalized trisamido ligand with Zr(NMe2)4 and GaMe3

“…Although the DFT is poor in taking in account the entropy term and no solvation effect was included in the computation, it can be observed that the difference in energy between the two models is marginal and within experimental error, with a DG and a DH respectively of À0.4 and À3.1 kcal mol À1 , favouring the coordination of the phosphine. The two structures minimized have ZreN bond lengths for the amido ligands of the tach between 2.065e2.085 Å and 2.078e2.105 Å for 4* and 4*eP, respectively, which compare well with the distances observed in the solid-state structures of known zirconium tach complexes (2.018e2.165 Å) [10]. The interaction between zirconium and triarylphosphines has been seldom structurally characterized and the bond lengths observed are between 2.644 and 3.019 Å [13].…”

“…No remaining amine proton is observed and the change in the coupling pattern of the protons on the cyclohexyl ring of 4 compared to 1 implies a change of conformation of the functionalized arms of the ligands from equatorial to the axial position. After comparison with the NMR spectra from Tilley's zirconium complexes [10], all the resonances on the 1 H NMR spectrum could be clearly assigned, with the broad peak at 4.56 ppm integrating for six protons belonging to the methylene protons on the functionalized arms. The resonance at 2.85 ppm is attributed to the remaining eNMe 2 moiety on the zirconium.…”

“…The ligand was initially designed to stabilize a Lewis acidic aluminum core using a trisamido tripodal interaction, in a manner already reported by Tilley and Turculet for zirconium analogues [10], to generate a novel family of ambiphilic ligands. The expected trisamido-coordination of aluminum was not observed, since the elimination of all alkyl groups from AlR 3 (R ¼ Me, iso-Bu) precursors was not possible (Scheme 1).…”

Cu(i) complexes based on cis, cis-1,3,5-tris(arylideneamino)cyclohexane ligands: synthesis, structure and CO binding

“…1-5 More generally, these ligands form a protected cavity around the metal centre which has been exploited in biomimetic and catalysis research. [6][7][8][9] Several synthetic routes for the generation of cis,cis-1,3,5-triaminocyclohexane (tach) ligands have been reported. [10][11][12] A general disadvantage of these methods is the undesirable generation of cis and trans isomers, which are difficult to separate.…”

Bridged Dinuclear Tripodal Tris(amido)phosphane Complexes of Titanium and Zirconium as Diligating Building Blocks for Organometallic Polymers

“…With metals in oxidation states greater than +3, these ligands preferentially form complexes where all three amido donors chelate to the metal, similar to other tripodal amido ligands. [14][15][16] Although the lone-pair of the phosphane donor is aimed away from the amido-chelated metal center, the minor lobe of this hybridized lone-pair orbital extends back towards the metal center. This through-space interaction [17] has been shown to influence the electronic param-afforded metal complexes of the type P(CH 2 NAr R ) 3 ZrNEt 2 (8a,b).…”