Synthesis of 3a,6a-diaza-1,4-diphosphapentalenes and their halogen derivatives. Specific features of the structure and behavior in solutions

Abstract

Such ketazines as azines of acetophenone and its substituted derivatives (p-F, m-Cl, p-I, p-Me, p-OMe), acetone, dibenzyl ketone, propiophenone, and indan-2-one were studied in the reaction with phosphorus(III) chloride. The possibility of the formation of 1,4-dichloro-3a,6a-diaza-1,4-diphosphapentalenes is largely determined by the nature of the starting ketazine. Diazadiphosphapentalene dichlorides exist in solution as a mixture of cisand trans-isomers, but crystallize exclusively as 1,4-trans-isomers. Reduction of 3a,6a-diaza-1,4-diphosphapentalene dichlorides with manganese in tetrahydrofuran gives the corresponding diazadiphosphapentalenes in 52-63% yield. The electrochemical properties of the obtained compounds were studied by cyclic voltammetry. Two dichlorides of 3a,6a-diaza-1,4-diphosphapentalenes were found to have anomalous oxidation potentials of 0.29 and 0.13 V related to the formation of free diazadiphosphapentalenes in solution as a result of disproportionation under the infl uence of the donor solvent, which was confi rmed by 31 P NMR spectroscopy, electronic absorption spectroscopy, and independent syntheses.

3 a,6 a‐Diaza‐1,4‐Diphosphapentalenes: Synthesis and Complexation with the Organic π‐Acceptor 1,2,4,5‐Tetracyanobenzene

“…Data from the single crystal X‐ray analysis indicate that the asymmetric unit cell contains half of the molecule. Compound 5 , like the vast majority of DDP‐dichlorides, [13] crystallizes as the trans isomer. The heteropentalene framework has a geometry close to planar, with the deviation of atoms from the averaged plane in the range of 0.008–0.068 Å.…”

A New Class of Two‐Deck Dicationic Heteropentalenes Existing by the Balance between Interdeck Aromaticity and Covalent P−P Bonding

“…Numbers and brief formulas of the obtained compounds are presented in Table 1, crystallographic characteristics -in Table S1 (Supporting Information). When considering this reaction, it is important to note the high mobility of chlorine atoms in dichlorides (DDPCl 2 ) [31] due to aromatic 6π stabilization (Schemes S1, S2 in the Supporting Information), which is similar to the formation of 1,3,2-and 1,2,3-diazaphosphenium cations from the corresponding Phalo-substituted diazaphosphols. [2,32] It is also worth noting the high activity of DDP in the dehalogenation reactions of some chlorophosphines.…”

“…In particular, cHexDDP is capable of converting Ph 2 PCl to Ph 2 P-PPh 2 and PCl 3 to red phosphorus in hexane at 20 °C). [31] The main structural feature of the two-deck dications is a "face-to-face" arrangement of the DDP-frames, in which the phosphorus atoms of neighboring decks are located opposite each other and form short contacts exceeding the length of the covalent bond PÀ P (> 2.22 Å). [33] In this case, the NÀ N bonds intersect in the projection.…”

“…General Remarks: The starting diazadiphosphapentalenes and their dichlorides (DDP and DDPCl 2 , Scheme 3) were obtained by previously developed procedures. [20,31,34] TMSOTf and Me 2 S•BCl 3 were purchased from Sigma Aldrich Chemical Co. All the compounds were synthesized under evacuation conditions or in an argon atmosphere of high purity. Solvents were purified following standard methods.…”

“…Since two-deck compounds (DDP) 2 X 2 contain charged fragments, a strong influence of the medium on the 31 P NMR spectra is unavoidable. In some solvents, many compounds have no 31 P signals at room temperature or represent a set of broad lines. For example, the 31 P{ 1 H} NMR spectrum for (EtMeDDP) 2 (OTf) 2 (3) shows no signal in THF, wide bands in CDCl 3 , and a singlet in CD 2 Cl 2 and acetonitrile, indicating the equivalence of all four phosphorus atoms in the two-deck DDP ditriflate.…”