Vanadate complexes bearing an imidazolidine-bridged bis(aryloxido) ligand: synthesis and solid state and solution structure

Abstract

A new imidazolidine-bridged bis(aryloxido) ligand precursor (H(2)L) [H(2)L = 2,2'-(imidazolidine-1,3-diylbis(methylene))bis(4-(1,1,3,3-tetramethylbutyl-2-yl)phenol)] was prepared in a relatively high yield (∼60%) via a single-step Mannich condensation of 4-(1,1,3,3-tetramethylbutyl)phenol, ethylenediamine and paraformaldehyde at 2:1:3 molar ratio and characterized by chemical and physical techniques including X-ray crystallography. Reactions of H(2)L with [VO(OEt)(3)] at 1:1 and 1:2 molar ratios in toluene afforded [V(L-κ(3)O,N,N,O)(O)(OEt)] (1) and [V(2)(μ-L-κ(4)O,N,N,O)(μ-OEt)(2)(O)(2)(OEt)(2)] (2), respectively. Alcoholysis of 1 with EtOH enables elimination of one molecule of H(2)L and the formation of 2. Compounds 1 and 2 were characterized by IR and NMR spectroscopy as well as ES-MS experiments. The definitive molecular structure of 2 was provided by a single-crystal analysis and revealed its dinuclear nature, featuring two octahedral vanadium centres bridged by both OEt groups and the L ligand. The (51)V, (1)H and (13)C NMR spectra as well as ES-MS showed that 2 does not stay intact in solution and undergoes dissociation to give 1 and [VO(OEt)(3)].

Vanadium complexes with multidentate amine bisphenols

“…18 The IR spectra show strong absorptions at 970 cm −1 for 2 and at 974 cm −1 for 3, corresponding to the VvO stretching frequencies. 6,10,19 The 1 H and 13 C NMR spectra of complexes 2 and 3 in CDCl 3 solution show the anticipated resonances for aminoalcohol bisphenolate ligands, once an apparent plane of symmetry in 3 is taken into account. The resonances could be assigned with the help of conventional 2D NMR correlation spectroscopy (COSY, NOESY, HSQC, HMBC), except for a couple of nearly-isochronous 13 C shifts from the tBu substituents of 2.…”

Crystal structure of the di-Mannich base 4,4′-dichloro-3,3′,5,5′-tetramethyl-2,2′-[imidazolidine-1,3-diylbis(methylene)]diphenol

“…As a continuation of our investigations of the Mannich reaction, we have synthesized a family of compounds of the type 2,2 0 -[imidazolidine-1,3-diylbis(methylene)]di(hydroxyaryl), from reactions between 1,3,6,8-tetrazatricyclo[4.4.1.1 3,8 ]dodecane (TATD) and phenols or naphthols (Rivera et al, 1993(Rivera et al, , 2005Rivera & Quevedo, 2013). Such compounds are known to be valuable in homogeneous catalysis (Kober et al, 2012) and for the preparation of tetrahydrosalens and heterocalixarenes . Mannich bases are also convenient models for studying the nature of hydrogen bonding and other weak non-covalent interactions, as they contain at least one phenolic or naphtholic hydroxy group as a proton donor, as well as an ortho-aminomethylgroup as a proton acceptor in the same molecule (Koll et al, 2006).…”

4,4′-Dimethyl-2,2′-{[2,3,3a,4,5,6,7,7a-octahydro-1H-benzimidazole-1,3-diyl]bis(methylene)}diphenol

“…For the structure of the original racemate, see: Rivera et al (2009). For the use of 1,3-diazaheterocyclic-bridged bis(phenols) in coordination chemistry, see: Kober et al (2012); Xu et al (2007). For the synthesis of the precursor, (2R,7R)- 1,8,10,12-tetraazatetracyclo[8.3.11 8,12 .0 2,7 ]pentadecane, see: Rivera et al (2012).…”

“…Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2008); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL2012. Chiral 1,3-diazaheterocyclic-bridged bis(phenols) form stable complexes with several metals and are of interest as ligands to metal complexes because they produce asymmetric coordination compounds (Xu et al, 2007;Kober et al, 2012) and therefore may be involved in enantioselective catalysis.…”