Zwitterionic d⁰ Metal Complexes [(Cy₂N)₃M]⁺[(μ-Me)B(C₆F₅)₃]⁻ (M = Ti, Zr, Hf) Derived from Tris(dicyclohexylamido)methyl Metal Precursors

Abstract

The synthesis and characterization of tris(dicyclohexyl)amido hafnium complexes ClHf(NCy 2 ) 3 (1-Hf) and MeHf(NCy 2 ) 3 (2-Hf) are presented. The reactions of the group 4 derivatives of this compound class (MeM(NCy 2 ) 3 ; M = Ti (2-Ti), Zr (2-Zr), Hf (2-Hf)) with B(C 6 F 5 ) 3 are investigated. Their reactions with strong Lewis acids lead to the first examples of zwitterionic group 4 complexes employing three amido ligands at the electrophilic metal center ([(Cy 2 N) 3 M] + [(μ-Me)B(C 6 F 5 ) 3 ] − ). The solid-state structures of all of the betaines (3-Ti, 3-Zr, 3-Hf) are presented and compared. In all homologues the methyl group is abstracted by the Lewis acid but remains in interaction with the electron-deficient metal center, resulting in a linearly bridging methyl group. The M•••C distances of 3-M are elongated by 0.25 Å (av) in comparison to 2-M.

Crystal structure of a zwitterionic azaallyl zirconiumamide complex bearing a Zr+-μ-CH3—B− moiety and one equivalent of n-hexane as a solvent

“…The Zr1Á Á ÁC37 bond length of 2.6616 (10) Å is considerably elongated in comparison with a Zr-C single bond of 2.286 (3) Å (Adler et al, 2014), and a new C37-B1 single bond of 1.6788 (14) Å is formed (Pyykkö & Atsumi, 2009). In contrast to our recently published results (Adler et al, 2016), the formation of a C C bond under abstraction of H 2 in one ligand was observed, giving rise to an azaallyl zirconium complex. The corresponding C31-C36 bond is significantly shortened to 1.3991 (14) Å compared to 1.5273 (85) Å (Adler et al, 2016).…”

“…In contrast to our recently published results (Adler et al, 2016), the formation of a C C bond under abstraction of H 2 in one ligand was observed, giving rise to an azaallyl zirconium complex. The corresponding C31-C36 bond is significantly shortened to 1.3991 (14) Å compared to 1.5273 (85) Å (Adler et al, 2016). The bond lengths Zr1-C36 of 2.5013 (10) Å and Zr1-N3 of 2.1524 (8) Å are similar to those found in other azaallyl zirconium complexes (Yuan et al, 2017).…”

“…The bond lengths Zr1-C36 of 2.5013 (10) Å and Zr1-N3 of 2.1524 (8) Å are similar to those found in other azaallyl zirconium complexes (Yuan et al, 2017). Additionally, the Zr1-N3-C31 bond angle is significantly narrowed to 91.97 (6) compared to 103.8 (3) (Adler et al, 2016), which underlines the coordination mode as an azaallyl ligand. The bond lengths to the N atoms of the di-cyclohexylamido ligands [Zr1-N1 = 2.0321 (8), Zr1-N2 = 2.0242 (8) Å ] lie within the range of comparable compounds (Adler et al, 2016) but are slightly shortened in comparison to the starting material [Zr1-N1 = 2.048 (2), Zr1-N2 = 2.054 (2) Å ; Adler et al, 2014].…”

Convenient Synthesis of Cationic Titanium Complexes with Tridentate Cp,N,P-Ligand Framework: FLP-Like Reactivity at the Ti–N Bond and Unexpected Ligand Hydrogenation Reaction

“…The 31 P­{ 1 H} NMR spectrum of 3a contains one resonance at δ 31 P­{ 1 H} 1.1 ppm, which is in the same range as for the free L2 (δ 31 P­{ 1 H} 6.7 ppm), indicating the same chemical environment at the phosphorus atom. The 1 H and 13 C­{ 1 H} NMR signals of the terminal titanium methyl groups of 3a , b are in the range for terminal monomethylated complexes of titanium. ,, …”

“…The 31 P{ 1 H} NMR spectrum of 3a contains one resonance at the terminal titanium methyl groups of 3a,b are in the range for terminal monomethylated complexes of titanium. 29,39,40 The abstraction of the methyl groups of 3a,b with the highly Lewis acidic borane B(C 6 F 5 ) 3 in toluene at room temperature resulted in the clean formation of the corresponding cationic complexes 4a,b in isolated yields of 88% each as air-and moisture-sensitive pale yellow (4a) or pale orange (4b) solids (Scheme 2). The targeted tridentate Cp,N,P-ligand framework is directly introduced in the coordination sphere of the metal.…”