Structure and magnetic behaviour of mono- and bimetallic chromium(iii) complexes of amine-bis(phenolate) ligands

Abstract

Two lithium amine-bis(phenolate) and four chromium(III) amine-bis(phenolate) complexes have been prepared. The diprotonated tripodal tetradentate ligand precursors 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)[O(2)NO](BuMe); 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4,6-tert-butylphenol), H(2)[O(2)NO](BuBu); 2-pyridylamino-N,N-bis(2-methylene-4,6-methylphenol), H(2)[O(2)NN'](MeMe); and 2-pyridylamino-N,N-bis(2-methylene-4,6-tert-butylphenol), H(2)[O(2)NN'](BuBu); can be lithiated using n-butyllithium. Isolation of the Li(2)[O(2)NO](RR') compounds generates dimeric {Li(2)[O(2)NO](RR')}(2) (R = t-Bu, R' = Me in 1 and R = R' = t-Bu in 2) in the solid state as shown by single-crystal X-ray diffraction. The lithiated ligands were used to prepare a series of Cr(III) complexes. Monometallic complexes are obtained when prepared and purified under strictly anhydrous conditions, giving CrCl(THF)[O(2)NO](RR') (R = t-Bu, R' = Me in 3 and R = R' = t-Bu in 4). However, bimetallic Cr complexes are obtained upon recrystallization in air, where adventitious water reacts with the complex resulting in protonation of one of the phenolate groups of the ligand and generating hydroxide, which bridges two Cr(III) centres. Solid-state single-crystal X-ray diffraction studies of {CrCl[O(2)NN'](MeMe)}(mu-HO){CrCl[HO(2)NN'](MeMe)}, 5, and {CrCl[O(2)NN'](BuBu)}(mu-HO){CrCl[HO(2)NN'](BuBu)}, 6, were performed. The paramagnetic Cr(III) complexes were also characterized by UV-vis spectroscopy, mass spectrometry and magnetic measurements.

Organic–inorganic hybrid supermicroporous chromium oxophenylphosphate with magnetic and catalytic properties

“…The best fitting curve corresponds to the g and J values from 2.012 70.04 to 1.98 70.01 and À2.3370.17 cm À 1 to À 2.17 7 0.17 cm À 1 , respectively with x values from 0.042 to 0.044 and TIP¼12 Â 10 À 3 emu/f.u. The g value is comparable to that commonly observed for Cr(III) [43] and the J value is significantly lower but compares well with that obtained for carbonato bridge Cr(III)…”

Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(ii) complexes

“…117- 121 The bridging acetate O-Co bond distances in 4-6 2 are caused by p → p* transitions involving the phenolate unitsabsorptions in this region are also observed in the spectra of the unmetallated ligand precursors. 33 Intense bands are also observed in the region between 300 and 450 nm, which are assigned to charge transfer transitions from the p p orbital (HOMO) of the phenolate oxygen to the d orbitals of Co II . The broad charge transfer bands obscure the high-energy visible region where ligand field transitions would be expected, particularly in donor solvents such as methanol.…”

Synthesis, Structure, and C–C Cross‐Coupling Activity of (Amine)bis(phenolato)iron(acac) Complexes

“…Absorptions around 240 nm are observed in the spectra of unmetalated ligand precursors but the absorptions around 280 nm are also observed in (amine)bis(phenolato) complexes not containing acac ligands. [17,78,85] Two absorptions between 340-550 nm are assigned as charge-transfer transitions from the ligand-to-metal (LMCT). The high energy bands around 340 nm arise from the transitions between the p π orbital of the phenolato oxygen and the half-filled d 3 .…”