Triple dehydrofluorination as a route to amidine-functionalized, aromatic phosphorus heterocycles.

An unexpected route to hitherto unknown amidine-functionalized phosphinines has been developed that is rapid and simple. Starting from primary amines and CF3-substituted λ3,σ2-phosphinines, a cascade of dehydrofluorination reactions leads selectively to ortho-amidinephosphinines. DFT calculations reveal that this unusual transformation can take place via a series of nucleophilic attacks at the electrophilic, low-coordinate phosphorus atom.

Highly flexible phosphabenzenes: a missing coordination mode of 2,4,6-triaryl-λ3-phosphinines.

The reaction of 2,4,6-triaryl-λ3-phosphinine-Cr(CO)3-π-complexes with [Rh(COD)2]BF4 leads to unusual diamagnetic Rh0-dimers, which contain two phosphinine-π-complexes acting as a bridging 2e--ligand towards the Rh2(CO)2 core. These compounds represent a missing coordination mode for the aromatic 6-membered phosphorus heterocycle.

Photochemical C(sp)-C(sp2) Bond Activation in Phosphaalkynes: A New Route to Reactive Terminal Cyaphido Complexes LnM-C≡P.

The photochemical activation of the C(sp)-C(sp2) bond in Pt(0)-η2-aryl-phosphaalkyne complexes leads selectively to coordination compounds of the type LnPt(aryl)(C≡P). The oxidative addition reaction is a novel, clean, and atom-economic route for the synthesis of reactive terminal Pt(II)-cyaphido complexes, which can undergo [3 + 2] cycloaddition reactions with organic azides, yielding the corresponding Pt(II)-triazaphospholato complexes. The C-C bond cleavage reaction is thermodynamically uphill. Upon heating, the reverse and quantitative reductive elimination toward the Pt(0)-phosphaalkyne-π-complex is observed.

Making Aromatic Phosphorus Heterocycles More Basic and Nucleophilic: Synthesis, Characterization and Reactivity of the First Phosphinine Selenide.

The synthesis and isolation of a phosphinine selenide was achieved for the first time by reacting red selenium with 2,6-bis(trimethylsilyl)phosphinine. The rather large coupling constant of 1 JP,Se =883 Hz is in line with a P-Se bond of high s-character. The σ-electron donating Me3 Si-substituents significantly increase the energy of the phosphorus lone pair and hence its basicity, making the heterocycle considerably more basic and nucleophilic than the unsubstituted phosphinine C5 H5 P, as confirmed by the calculated gas phase basicities. NBO calculations further reveal that the lone pairs of the selenium atom are stabilized through donor-acceptor interactions with antibonding orbitals of the aromatic ring. The novel phosphinine selenide shows a distinct reactivity towards hexafluoro-2-butyne, Au(I)Cl as well as i PrOH. Our results pave the way for new perspectives in the chemistry of phosphorus in low coordination.

2-(Dimethylamino)phosphinine: A Phosphorus-Containing Aniline Derivative.

The yet unknown 2-amino-substituted λ3 ,σ2 -phosphinines are phosphorus-containing aniline derivatives. Calculations show that the strong interaction of the π-donating NR2  group with the aromatic system results in a high π-density at the phosphorus atom. We could now synthesize 2-N(CH3 )2 -functionalized phosphinines, starting from a 3-N(CH3 )2 -substituted 2-pyrone and (CH3 )3 Si-C≡P. Their reaction with CuBr⋅S(CH3 )2 affords CuI  complexes with the first example of a neutral phosphinine acting as a rare bridging µ2 -P-4e donor-ligand between two CuI  centers. Our experimental and theoretical investigations show that 2-aminophosphinines are missing links in the series of known 2-donor-functionalized phosphinines.