Pal, Chandan Kumar ; Chattopadhyay, Surajit ; Sinha, Chittaranjan ; Chakravorty, Animesh (1996) A bis(azo-imine)palladium(II) system with 10 ligand π electrons. Synthesis, structure, serial redox, and relationship to bis(azooximates) and other species Inorganic Chemistry, 35 (9). pp. 2442-2447. ISSN 0020-1669
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic950361t
Related URL: http://dx.doi.org/10.1021/ic950361t
Abstract
The first azo-imine chelate system, Pd(N(H)C(R)NNPh)2 (Pd(RA)2), has been isolated in the form of diamagnetic solids by the 6e--6H+ reduction of bis(phenylazooximato)palladium(II), Pd(N(O)C(R)NNPh)2 (abbreviated Pd(RB)2), with ascorbic acid in a mixed solvent (R = Ph, α-naphthyl). Selected spectral features are described. The X-ray structures of Pd(PhA)2 and Pd(PhB)2 have revealed trans-planar geometry consistent with metal oxidation state of +2. Bond length trends within the chelate rings are rationalized in terms of steric and electronic factors. In Pd(PhA)2 a total of 10 ligand π electrons are present, each formally monoanionic ligand contributing five. Model EHMO studies have revealed that the filled HOMO (au) in Pd(RA)2 is a bonding combination of two ligand π∗ orbitals with large azo contributions. The LUMO (bg) is roughly the corresponding antibonding combination. The outer p-electron configuration of Pd(RA)2 is (au)2(bg)0. Four successive voltammetric responses, two oxidative and two reductive, are observed. The E1/2 range is -1.3 to +0.8 V vs SCE for Pd(PhA)2 in a 1:9 MeCN-CH2Cl2 mixture (Pt electrode). EPR and electronic spectra of the electrogenerated one-electron-oxidized complex Pd(PhA)2+ are described. The azo-imine system is compared with imine-imine and azo-azo systems. Crystal data for the complexes are as follows. Pd(PhA)2: crystal system monoclinic; space group C2/c; a = 18.167(5) Å, b = 7.420(3)Å, c = 16.527(6) Å; β = 92.70(3)°; V = 2225(1) Å3; Z = 4; R = 2.61%, Rw = 3.58%. Pd(PhB)2: crystal system monoclinic; space group P21/n; a = 5.735(5) Å, b = 10.797(6) Å, c = 18.022(11) Å; β = 97.73(6) Å; V = 1105(1) Å3; Z = 2; R = 3.37%; Rw = 3.40%.
| Item Type: | Article |
|---|---|
| Source: | Copyright of this article belongs to American Chemical Society. |
| ID Code: | 6787 |
| Deposited On: | 22 Oct 2010 06:48 |
| Last Modified: | 31 Jan 2011 07:02 |
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