Bis[2-(2H-benzotriazol-2-yl)-4-methylphenolato]palladium(II)

In the title complex, [Pd(C13H10N3O)2], the PdII atom is tetracoordinated by two N atoms and two O atoms from two bidentate 2-(2H-benzotriazol-2-yl)-4-methylphenolate ligands, forming a square-planar environment. The asymmetric unit contains one half molecule in which the Pd atom lies on a centre of symmetry.

In the title complex, [Pd(C 13 H 10 N 3 O) 2 ], the Pd II atom is tetracoordinated by two N atoms and two O atoms from two bidentate 2-(2H-benzotriazol-2-yl)-4-methylphenolate ligands, forming a square-planar environment. The asymmetric unit contains one half molecule in which the Pd atom lies on a centre of symmetry.

Experimental
Crystal data [Pd(C 13

Comment
During the last 2 decades, the synthesis and characterization of polypeptides is an interesting research field that received considerable attentions. The chemical synthesis of high molecular weight poly(α-peptides) can be accomplished by the ring-opening polymerization of α-amino acid N-carboxyanhydride (α-NCA) initiated by suitable initiators/catalysts. Among these initiators/catalysts, the Ni, Co, Fe, Pd, Pt, Ru, Ir, and Al complexes modified by adequate ligands have been shown to be active initiators/catalysts for NCA polymerization (Kricheldorf, 2006). In particular, Deming, (1997), reported that Schiff base ligand containing primary amine complexes of Co, Ni, Pd, and Cu metal ion could efficiently catalyze polymerizations of γ-benzyl L-glutamate N-carboxyanhydride (Glu-NCA) to achieve poly(γ-benzyl L-glutamate). Recently, Peng et al., 2008, has also reported the Pt complex supported by amido-sulfonamidate ligand and this complex has been demonstrated as efficient initiators for living ROP of α-NCA. Most recently, we have successfully synthesized and structural characterized a N,N',O-tridentate Schiff base of Cu(II) complex (Lin et al., 2008). We report herein the synthesis and crystal structure of N,O-bidentate benzotriazol-phenolate ligands incorporated Pd II complex (I), a potential catalyst for chemical synthesis of poly(peptides) (Scheme 1).
The solid structure of (I) reveals a monomeric Pd II complex ( Fig. 1) containing two six-member rings coordinated from these two N,O-bidentate benzotriazol-phenolate ligands. It was found that the asymmetric unit has one half of molecule in which the Pd atom lies on a centre of symmetry. The Pd atom is tetra-coordinated with a normal square planar environment in which two N atoms and two O atoms are coplanar. The two N atoms and two O atoms around Pd atom are trans to each other with bond angle of O-Pd-N1 of 91.74 (7)°. The distances between the Pd atom and O and N1 are 1.9676 (15)Å, 1.9986 (18)Å, respectively. These bond distances of Pd-O and Pd-N1 are around 0.1 Å shorter to those found in the other Schiff base Pd II complexes (Yang et al.,1993). The bond distance of imine bond, C7-N1 of the benzotriazol group is 1.359 (3)Å and is 0.01Å longer than the other imine bond, C12-N3 (1.348 (3)Å). This is probably due to the existing coordination bond of the former nitrogen, N1.

Refinement
The H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C-H = 0.93 and 0.96Å with U iso (H) = 1.2 and 1.5U eq (C).  Fig. 1. A view of the title molecule I with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius. Symmetry code: (i) 2-x, -y, 1-z.