Mono-, di- and tetra-zinc complexes derived from an amino-benzotriazole phenolate ligand containing a bulkier N-alkyl pendant arm: synthesis, structure and catalysis for ring-opening polymerization of cyclic esters.

Zinc complexes constructed from the amino-modified benzotriazole phenol pro-ligand, 2-(2H-benzotriazol-2-yl)-6-((diisopropylamino)methyl)-4-(2,4,4-trimethylpentan-2-yl)phenol ((C8DIA)BTP-H, 1), were synthesized stepwise and structurally characterized. The reaction of (C8DIA)BTP-H (1) with one equivalent of diethyl zinc (ZnEt2) generates a dimeric and four-coordinated zinc complex, [(µ-(C8DIA)BTP)ZnEt]2 (2), which is doubly bridged by two phenolate groups of C8DIABTP ligands. Further reaction of 2 with benzyl alcohol (BnOH) in stoichiometric proportions affords a tetranuclear zinc benzylalkoxide complex [(µ-OBn)((C8DIA)BTP)Zn]4 (3) that possesses a saddle-shaped core with four µ2-bridging benzylalkoxy groups upon four Zn centres. Interestingly, the di-nuclear Zn alkoxide [(µ-OBn)((C8DIA)BTP)Zn(DMAP)]2 (4) could be prepared by treatment of 3 with a stoichiometric amount of 4-(dimethylamino)pyridine (DMAP). ZnEt2 reacts with two equivalents of 1 in the presence of DMAP (1.0 mol equiv.) to yield a five-coordinated mononuclear zinc complex, [((C8DIA)BTP)2Zn(DMAP)] (5). All complexes adopt an N,O-bidentate coordination mode from the phenoxy oxygen atom and benzotriazole nitrogen atom, in which the nitrogen atom of the pendent arm substituent is not coordinated to the zinc centre. Ring-opening polymerization of ε-caprolactone and ß-butyrolactone catalysed by 2 and 3 was investigated.

Zinc and magnesium complexes incorporated by bis(amine) benzotriazole phenoxide ligand: synthesis, characterization, photoluminescent properties and catalysis for ring-opening polymerization of lactide.

A new bis(amine) benzotriazole phenoxide ligand, (C8NN)BTP-H (1) was prepared from the Mannich condensation of 2-(2H-benzotriazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)phenol with the mixtures of excess paraformaldehyde and N,N,N-trimethylethylenediamine under reflux conditions. Zinc and magnesium complexes bearing the N,N,O-tridentate (C8NN)BTP ligand were synthesized and fully characterized. The reaction of (C8NN)BTP-H with ZnEt(2) (1.2 molar equiv.) in toluene gives the monomeric tetra-coordinated zinc complex [((C8NN)BTP)ZnEt] (2). The homoleptic and monomeric complexes [((C8NN)BTP)(2)M] (M = Zn (3) and M = Mg (4)) result from treatment of ZnEt(2) or Mg(n)Bu(2) with (C8NN)BTP-H (two equiv.), in which the metal center is hexa-coordinated by two tridentate (C8NN)BTP ligands. Luminescent properties and catalysis for lactide (LA) polymerizations of complexes 2-4 are studied. Complexes 2-4 produce bright green fluorescence with emission maxima ranging from 510 to 520 nm in the solid state. Experimental results indicate that complex 2 catalyzes the ring-opening polymerization of LA in the presence of 9-anthracenemethanol (9-AnOH) with efficient catalytic activities in a controlled fashion, yielding poly(rac-lactide) with a slight isotactic predominance (P(m) = 0.59).

Bis[2-(2H-benzotriazol-2-yl)-4-methyl-6-(phenyl-imino-methyl-κN)phenolato-κO]palladium(II).

In the title complex, [Pd(C(20)H(15)N(4)O)(2)], the Pd(II) atom is tetra-coordinated by two N atoms and two O atoms from two bidentate imine-benzotriazole phenolate ligands, forming a square-planar environment. The asymmetric unit contains two half-mol-ecules in both of which the Pd(II) atom lies on a centre of symmetry. The average distances between the Pd(II) atom and the coordinated O and N atoms are 1.9831 (12) and 2.012 (2) Å, respectively.

(E)-2-(2H-Benzotriazol-2-yl)-4-methyl-6-(phenyl-imino-meth-yl)phenol.

In the title compound, C(20)H(16)N(4)O, the non-H atoms of the benzotriazole ring system and those of the methyl-phenol group are essentially coplanar, with an r.m.s. deviation of 0.004 (2) Å. The mean plane of these atoms forms a dihedral angle of 60.9 (2)° with the phenyl ring. There is an intra-molecular O-H⋯N hydrogen bond between the phenol and benzotriazole groups.