Structures, Redox and Spectroscopic Properties of Pd^II and Pt^II Complexes Containing an Azo Functionality

Abstract

The complexes [PdCl 2 (pap)] (1) and [PtCl 2 (pap)] (2; pap = 2-phenylazopyridine) were synthesized by treating PdCl 2 or K 2 PtCl 4 , respectively, with pap and characterized by 1 H NMR spectroscopy and elemental analysis. Both these complexes, together with the previously reported complex [(az)Pd(µ-Cl) 2 -Pd(az)] (3; az = azobenzene), were also characterized by Xray crystallography. The structures of 1, 2, and 3 show a slightly elongated N-N azo double bond due to back-donation from the metal centers and a twisting of the uncoordinated part of the ligands with respect to the rest of the molecule. Cyclic voltammetry of 1, 2, 3, and the related complex

Isomeric separation in donor–acceptor systems of Pd(ii) and Pt(ii) and a combined structural, electrochemical and spectroelectrochemical study

“…Just like the oxidation processes, the reduction potentials for the palladium complexes 1a (E 1/2 red1 = -1.12 V) and 3a (E 1/2 red1 = -1.07 V) are cathodically shifted compared to their platinum analogues 2a (E 1/2 red1 = -0.90 V) and 4a (E 1/2 red1 = -0.82 V); the shift, however, is less compared to that for the oxidation potentials ( Table 2). The trend in the reduction potentials observed here is the opposite of what was observed for the precursor complexes [Pd(pap)Cl 2 ] and [Pt(pap)Cl 2 ], 44 where the Pd(II) complex (E 1/2 = -0.56 V) has a lower negative reduction potential compared to that of the Pt(II) analogue (E 1/2 = -0.79 V). Pd(II) is normally capable of a better s-polarization effect compared to Pt(II) and this phenomenon is responsible for the lower negative reduction potential of [Pd(pap)Cl 2 ] compared to [Pt(pap)Cl 2 ].…”

Structures, Redox and Spectroscopic Properties of PdII and PtII Complexes Containing an Azo Functionality

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During the galley correction stage of this paper, [1] 2 Cl 2 ] and the X-ray crystal structure of [Pd 2 (az) 2 Cl 2 ] had not been reported previously, and the studies in our paper corroborate the original conclusions on the structure. [3] The authors express their regret for any inconvenience that might have arisen, and apologise to the original authors and the editors of Eur.

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Computational study of the cyclopalladation mechanism of azobenzene with PdCl2 in N,N-dimethylformamide

“…For example, the crystal structure of the double cyclopalladated azobenzene obtained in dmf [13,15] displays monomeric molecules with Pd atoms coordinated by dmf molecules as ancillary ligands. On the other hand, the crystal structure of the monocyclopalladated product obtained in a mixture of dioxan and water has a dimeric structure [24] analogous to 3a,b, with two monomer units bridged by a pair of chlorine atoms. The calculated free energy difference between the monomer and dimer structures in dmf is 0.8 kcal/mol per mononuclear unit in favor of the dimer.…”

“…Interestingly, although the cyclopalladation product of azobenzene was isolated more than 40 years ago, its crystallographic structure has been only recently determined [24]. It has a dimeric structure with two cyclopalladated ligands bridged by two chlorine atoms in the centrosymmetric arrangement.…”