Vanadium(V) Complexes of a Chelating Dianionic [ONNO]-Type Amine Bis(Phenolate) Ligand:  Synthesis and Solid State and Solution Structures

Abstract

The reaction between VO(OR)(3) (R = (i)()Pr, (t)()Bu, CH(2)CF(3)) and the chelating dianionic bis(phenoxy)amine ligand [ONNO]H(2) affords a mixture of two isomers (A and B in a ratio A:B approximately 3:1) formulated as VO(OR)[ONNO] (1a-c) (R = (i)()Pr (1a), (t)Bu (1b), CH(2)CF(3) (1c)). Multinuclear and NOESY NMR spectroscopy experiments were able to determine the structure in solution of the complexes. Both isomers have the symmetry-related phenolate groups in a trans configuration, the difference arising from the different configuration of the oxo and alkoxo ligands being located either cis (in isomer A) or trans (in isomer B) to the tripodal amino nitrogen donor atom and the (dimethylamino)ethyl sidearm respectively for the oxo and the alkoxo ligands. Crystals of isomer A (cis-1a) were obtained, and the structure determination confirms the arrangement of the ligands around the vanadium center. Analogue complexes VO(X)[ONNO] (X = Cl (2); X = N(3) (3)) were prepared by reacting equimolar amount of [ONNO]H(2) and VO(X)(n)(OR)(3-n) (X = Cl, R = Et, n = 1; X = N(3), R = (i)Pr, n = 2) at ambient temperature. Compounds 2 and 3 were further characterized by NMR spectroscopy experiments and X-ray structure determination. For both 2 and 3, a single isomer is obtained, having a trans-(O,O) configuration for the phenolate groups and a trans configuration of the oxo ligand in respect to the tripodal amino nitrogen donor atom. Finally, complex 2 could also be obtained by chlorination of 1a or 3 using a large excess of ClSiMe(3) in refluxing toluene.

Paramagnetic Chloro‐, Alkoxo‐, or Azidovanadium(IV) Complexes Supported by an [ONNO]‐Type Amine Bis(phenolate) Ligand

“…was necessary, in dilute refluxing toluene solution, followed by slow cooling of the solution to room temperature, to afford dark blue crystals of the dichloro complex [VCl 2 {ONNO}] (4) (yield: 96%) (Scheme 2). Addition of pyridine or PMe 3 to complex 2 did not affect its EPR spectrum (in particular, no coupling with the 31 P phosphorus nucleus of PMe 3 was observed) or the color of the solution, suggesting that the sidearm NMe 2 group is sufficiently tightly bound to the metal not to be displaced by strong donors (as in our vanadium()[ONNO] complexes [12] ).…”

“…[9b,20] We showed previously that Me 3 SiCl could replace an azido group by a chlorine atom in oxo-vanadium() complexes, [12] and thus it was interesting to react the bis-azido complex 1 with Me 3 SiCl. Unfortunately, the reaction did not proceed to completion even under forcing conditions in refluxing toluene.…”

“…[5a] As our interest lies strongly in vanadium chemistry with various supporting ligand environments, [9] in particular those that could help stabilize the formal oxidation state (ϩ or ϩ) of the vanadium center (and thus avoid the reduction to inactive V II species by the alkylaluminum cocatalyst) during the vanadium-catalyzed polymerization of olefins, [10,11] we have recently described the synthesis of a series of oxovanadium() complexes with the ancillary amine bis(phenolate) [ONNO]-type ligand (Figure 1), [12] and demonstrated interesting features in the solution and the solid-state structure of these complexes. In the present article, we wish to report on the synthesis, structure, EPR spectroscopy, and magnetism of [ONNO] ligand that has phenolate groups in a trans configuration, with both amino-nitrogen donor atoms of the ligand coordinated to the octahedral vanadium center.…”

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

“…Copolymer structure characterization Unsaturated end group analysis was carried out on poly(ethylene-co-1-octene) samples with different 1-octene content produced with VCl 2 (salenCl 2 )/EtAlCl 2 (Table 1, run 8, 11, and 15) and TiCl 2 (salenCl 2 )/MAO (Table 3, run 19,20). The exemplary spectra are presented in Fig.…”

“…Their specific catalytic properties made them applicable in the production of poly(ethylene-co-propylene) and poly(ethyleneco-propylene-co-diene) elastomers [8,14,15]. Hence, much interest was attracted by postmetallocene complexes which had vanadium as the central metal, both for homoand copolymerization of olefins [5][6][7][15][16][17][18][19][20][21]. Nomura and Wang [7] used (arylimino)(aryloxo)vanadium(V) complexes in ethylene/1-hexene copolymerization.…”