1,4-Dihydro-1,4-diarsinine-Bridged Dinuclear trans-Dihaloplatinum(II) Complexes: Synthesis and Controlled Pt−Pt Interaction by Halogen Substitution Induced Conformational Change

Abstract

Mono- and dinuclear trans-dichloroplatinum(II) complexes, i.e., trans-PtCl2(cis-DHDAtBu)2 and trans,trans-Pt2Cl4(cis-DHDAtBu)2, respectively, using cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(tert-butoxycarbonyl)-1,4-diarsinine (cis-DHDAtBu), which was prepared by the radical reaction of pentamethylcyclopentaarsine (cyclo-(MeAs)5) and di-tert-butyl acetylenedicarboxylate, were obtained individually as only products by stoichiometric addition of cis-bis(benzonitrile)dichloroplatinum to cis-DHDAtBu. Replacement of chloride with iodide by adding KI into acetone solutions of trans-PtCl2(cis-DHDAtBu)2 and trans,trans-Pt2Cl4(cis-DHDAtBu)2 gave trans-PtI2(cis-DHDAtBu)2 and trans,trans-Pt2I4(cis-DHDAtBu)2, respectively. The structures of all the obtained compounds were confirmed by 1H and 13C NMR spectra, X-ray crystallography, and elemental analysis. The interior angles around the arsenic and the As−CC bond angle were significantly varied in a series of the present platinum(II) complexes. These observations suggest that the flexibility of the bond angles around the arsenic center is an inherent property in the present organoarsenic compounds. The intermetallic interaction was induced in the dinuclear platinum(II) “face-to-face” complex using cis-DHDAtBu by the replacement of chloride with iodide. The distance of the Pt−Pt of trans,trans-Pt2I4(cis-DHDAtBu)2 was shortened compared with that of trans,trans-Pt2Cl4(cis-DHDAtBu)2, and the new broad absorption band at around 562 nm was observed in the solution of trans,trans-Pt2I4(cis-DHDAtBu)2. Density functional theory calculations indicate that the frontier molecular orbitals in trans,trans-Pt2Cl4(cis-DHDAOH)2, in which H atom surrogates were used in place of the tBu group, show no d−d interaction orbitals. On the other hand, the HOMO level in trans,trans-Pt2I4(cis-DHDAOH)2 has mainly d xz contributions in the π*-antibonding MO.

Organic Vapor Triggered Repeatable On–Off Crystalline-State Luminescence Switching

“…During the course of our studies on the synthesis of a number of different complexation structures of 1,4-dihydro-1,4-diarsinines as cyclic ditopic organoarsenic ligands to transition metals, we have found that flexibility of the bond angles around the arsenic center is an inherent property of the organoarsenic compounds. 10 The flexibility of the arsenic ligands might be a main reason for the nonluminescent properties of most of these organoarsenic complexes at room temperature, in contrast to their phosphorus analogues. We found, as described herein, that a nonporous crystalline solid of an organoarsenic platinum(II) complex shows on−off solid-state luminescence switching through reversible and guest-selective uptake and escape.…”

Structural diversity in the coordination of 1,4‐dihydro‐1,4‐diarsinine as a cyclic ditopic organoarsenic ligand to metal ions

“…The reasons for the quantitative formations of these complexes are the structural advantage of the ligands and properties of the arsenic donor. The interior angles at around the arsenic and the As C C bond angles were significantly varied in a series of the platinum(II) complexes [19]. These observations suggest that the flexibility of the bond angles at around the arsenic center is inherent property in the present cyclic ditopic organoarsenic ligands and the flexibility might be the main reason for stabilization of the strained complexes and enable synthesis of the unique structured complexes.…”

“…The 1 H NMR spectrum of PtAu 2 Cl 4 (cisDHDAtBu) 2 in CDCl 3 at room temperature shows the sharp two peaks at δ 1.97 ppm and 1.94 ppm corresponding to the protons of the methyl groups on the arsenic atoms; each peak is attributed to the coordinated methylarsine group to Pt and Au, respectively. In the 1 H NMR spectrum of transPtCl 2 (cis-DHDAtBu) 2 in CDCl 3 at room temperature, the sharp two peaks are observed at δ 1.99 ppm and 1.37 ppm corresponding to the protons of the methyl groups on the arsenic atoms; each peak is attributed to the coordinated methylarsine group and the uncoordinated one, respectively [19]. The later peak is shifted to a downfield by the complexation with Au.…”

“…We have previously reported that a mononuclear platinum(II) complex (trans-PtCl 2 (cis-DHDAtBu) 2 ) was obtained by complexation of cis-DHDAtBu with a half-equimolar amount of PtCl 2 (PhCN) 2 (Scheme 1) [19]. The ORTEP drawing of the mononuclear platinum(II) complex shows that the two molecules of cis-DHDAtBu were bridged with the platinum ion.…”

“…However, complexes using them had poor solubility, and they have not been used as ligands. Recently, we have reported stoichiometric synthesis of mono-and dinuclear trans-dichloropalladium(II) and transdichloroplatinum(II) complexes [18,19], which are usually unstable to convert to cis-complexes when conventional ligands are used [20]. The reasons for the quantitative formations of these complexes are the structural advantage of the ligands and properties of the arsenic donor.…”