Bis(μ-phenylmethanolato)bis({4-[(E)-(4-tert-butylphenyl)(2-pyridylmethylimino)methyl]-3-methyl-1-phenyl-1H-pyrazol-5-olato}zinc(II))

In the title centrosymmetric dimeric ZnII complex, [Zn2(C27H27N4O)2(C7H7O)2], the ZnII center is coordinated by two N atoms and one O atom of the ketiminate ligand and two bridging O atoms of the benzylalkoxy groups. The geometry around the ZnII ions is distorted trigonal-bipyramidal.

In the title centrosymmetric dimeric Zn II complex, [Zn 2 (C 27 H 27 N 4 O) 2 (C 7 H 7 O) 2 ], the Zn II center is coordinated by two N atoms and one O atom of the ketiminate ligand and two bridging O atoms of the benzylalkoxy groups. The geometry around the Zn II ions is distorted trigonal-bipyramidal.

S1. Comment
Polyesters such as poly(ε-caprolactone) (PCL) and poly(lactide) (PLA) and their copolymers have attracted intensive attention due to their potential applications in many fields (Gref et al.,1994;Jeong et al., 1997). The major polymerization methods for these polymers are the ring-opening polymerization (ROP) of cyclic esters. Many zinc complexes with various ligands were effective initiator/catalyst for the ROP of cyclic esters (Chamberlain et al., 2001;Williams et al., 2003;Dechy-Cabaret et al. 2004, Chen, et al., 2005Wu, et al., 2006;Hung et al., 2008Hung et al., , 2009. Tripodal tridentate ligand supported zinc complexes have been synthesized and used for the polymerization of lactides and the polymerization is living with relatively low polydispersities (Chisholm et al., 2000). Recently, a series of zinc alkoxides (Yu, et al., 2002;Lee, et al., 2007) coordinated with simple NNO-tridentate ketiminate ligands has been synthesized and these derivatives showed highly catalytic activity with regard to the ROP of lactides. However, these complexes had no (or little) stereoselectivities for the polymerization of rac-lactides. In order to obtain catalytic activity as well as enhance stereoselectivity of the corresponding metal alkoxides, we (Huang, et al., 2009) have developed a unsymmetric NNOketiminate system derived from 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one. In the presence of pyrazole fused a chelating arm, the metal derivatives can be stabilized by an extensive π-conjugate system. In this study, we reported the

S2. Experimental
The ml), and then benzyl alcohol (0.21 ml, 2.0 mmol) was added at 0°C. Continuously stirring at 0°C for another 3 h, the mixture initially turned colorless and then into white turbid. After filtration and washing with cooled toluene three times, a white powder was obtained. The resulting powder was recrystallized with a mixted dichloromathane and hexane solution to yield white crystals.

S3. Refinement
The methyl H atoms were constrained to an ideal geometry with C-H distances of 0.96 Å and U iso (H) = 1.5U eq (C), but each group was allowed to rotate freely about its C-C bond. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H distances in the range 0.95-1.00 Å and U iso (H) =1.2U eq (C).

Figure 1
A view of the molecular structure of the title compound with displacement ellipsoids shown at the 20% probability level.

Bis(µ-phenylmethanolato)bis({4-[(E)-(4-tert-butylphenyl)(2-pyridylmethylimino)methyl]-3-methyl-1-phenyl-1Hpyrazol-5-olato}zinc(II))
Crystal data  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.