Synthesis and characterisation of neutral and cationic alkyl aluminium complexes bearing N,O-Schiff base chelates with pendant donor arms

Abstract

The Schiff base ligands [3,5-Bu t 2 -2-(OH)C 6 H 2 CH᎐ ᎐ NL] [L = CH 2 CH 2 NMe 2 (1a), 2-(PhO)C 6 H 4 (1b), 2-CH 2 C 5 H 3 N (1c), 8-C 9 H 6 N (quinoline) (1d) and 2-(PPh 2 )C 6 H 4 (1e)] are accessed in good yields (>85%) via standard imine condensation reactions. Reaction of 1a-e with Me 3 Al at room temperature affords the corresponding complexes [(3,5-Bu t 2 -2-(O)C 6 H 2 CH᎐ ᎐ NL)AlMe 2 ] (2a-e); in the case of L = 8-quinoline, the same reaction conducted in refluxing toluene affords binuclear {[3,5-Bu t 2 -2-(O)C 6 H 2 CHMeN-8-C 9 H 6 N]AlMe} 2 (3) by methyl migration from metal to ligand. Further reaction of the dimethyl compounds with B(C 6 F 5 ) 3 in CD 2 Cl 2 or C 6 D 6 affords the cationic systems [The crystal structures of 2a, 2c, 2e and 3 have been determined. In 2a and 2c the respective ligands bind to the metal centre via all three heteroatoms, the aluminium having a trigonal bipyramidal geometry, whereas in 2e coordination is via nitrogen and oxygen only, and the aluminium is tetrahedral. Complex 3 has a dimeric structure with the ligand adopting both tridentate and binucleating roles; the aluminium centres are trigonal bipyramidal.

Pseudo‐Octahedral Schiff Base Nickel(II) Complexes: Does Single Oxidation Always Lead to the Nickel(III) Valence Tautomer?

“…HL 2 , [8,9] HL 3 , [9,10] and HL 5[8a] have been described previously. Treatment of 2-tert-butyl-6-formyl-4-methoxyphenol with 8-aminoquinoline affords HL 4 .…”

“…of a tridentate ligand to coordinate a single metal ion. [5,[8][9][10] The prototypical asymmetric Schiff base ligand HL 1 ( Figure 1) coordinates with two nitrogen atoms (from one pivotal imine and one terminal pyridine group) as well as an oxygen atom (from the redox-active phenolate group). Modifications realized on HL 1 concern the electronic properties of the phenol para substituent (HL 2 ), the hybridization of the pivotal nitrogen atom (HL 3 ), and the N-donor properties of the pyridine group (HL [4][5] ).…”

An Unusual N‐Bridged (Amido)(hydrido)(phenoxido)aluminium Dinuclear Compound – The Role of Nitrogen Substituents in Determining Nuclearity: A Combined Experimental and Theoretical Study

“…As previously stated, complexes containing Schiff base ligands usually present mononuclear structures. [32,34,38] However, dinuclear geometries are also described [22] in which the phenolic oxygen atoms of the ligands bridge adjacent aluminium centres. [40,46] Surprisingly, in 5 the two aluminium centres are linked by µ 2 -N(amido) atoms to form a central planar Al 2 N 2 ring in a clearly preferential disposition compared with the most common Al 2 O 2 ring.…”

“…This structural behaviour contrasts with that found in the literature: O-bridging structures are generally observed in polynuclear aluminium derivatives supported by bridging phenoxido-imino and related ligands. [22,25,39,40] …”

Synthesis and Structure of Ion-Pairs Ytterbium Chloride Bearing Tridentate [O,N,N] Schiff-Base Ligand

“…(Scheme 2) [13] , 文献也曾报道用稀土烷基化合物和席夫 碱进行质解反应时, 往往会发生烷基加成亚胺键的现 象 [14] . 用锂盐与稀土氯化物反应时, 由于氯化锂在有机 溶剂中溶解性比较大, 较难除去, 所以在结晶产物中往 往会夹杂锂盐, 形成离子型配合物(Eq.…”