A homonuclear π-system with a singlet carbene-type α and a nucleophilic β phosphorus – the first use in P-heterocyclic synthesis

Abstract

Reactions of a μ2-(η1,η2)-dinuclear diphosphene tungsten(0) complex with DMAD, PTAD and DEAD was applied to P-heterocyclic synthesis, thus combining a singlet carbene-type and a nucleophilic reactivity of a homonuclear π-system.

On Haptotropic Rearrangements of Diphosphene and Diarsene Ligands in Titanium Complexes

“…These can both be attributed to complete dissociation of the diphosphene ligand. An asymmetrical coordination at titanium is also indicated in the 1 H and 13 C{ 1 H} NMR spectra by two singlets (δ( 1 H) = 5.21, 5.30 ppm; δ( 13 C{ 1 H}) = 102.8, 104.0 ppm) for two inequivalent Cp ligands. The combined NMR spectroscopic data suggested the formation of the complex Cp 2 Ti-(NCMe)(P 2 Tip 2 ) (2 a), with an η 1 -diphosphene ligand.…”

“…While haptotropic rearrangements in diazene systems were the subject of numerous studies, [12] these are surprisingly rare in the coordination chemistry of their heavier congeners. [13] Photochemically induced η 2 to η 1 rearrangements in cationic diphosphene complexes of iron and molybdenum were recently studied by Tonner-Zech, Wolf, Weigand and co-workers (Scheme 2, top). [14] Interestingly, these reactions could be reversed when irradiated at a different wave length.…”

Elimination reactions in 1,4-diphosphinine chemistry: mixed-valence intermediates and 1,1- vs. 1,4-elimination pathways

“…[8][9][10] Research on phosphinines remains very active, 11,12 14 the first isolation of a 1,4-diphosphinine was not achieved until 2017 when Streubel et al synthesised a tricyclic, imidazole-2-thione-fused derivative (IX, Chart 2). 15 Since then, the scope of fused five-membered heterocycles has expanded, i.e., incorporating 1,3-thiazole-and 1,3-dithiole-2thiones 16,17 as well as different substitutions in C 2 -position, i.e., selones, 18 TTF-motifs 19 and a 2-phenylimidazolium-fused example, the latter was reported by Ghadwal et al 20 Several different reactivity studies on 1,4-diphosphinines IX have been performed, such as [4 + 2]-cycloaddition [21][22][23] and 1,4-addition reactions, 16,22 the latter yielding σ 3 λ 3 -1,4-dihydro-1,4-diphosphinine structural motifs. In the same vein, a σ 4 λ 5 -1,4-dihydro-1,4-diphosphinine could be achieved by oxidation with H 2 O 2 in the presence of BaCl 2 .…”