A versatile, high-yielding synthesis of NHC-stabilized [PCl(2)](+) and [PCl](2+) phosphorus synthons has been achieved by using an "onio-substituent transfer" reagent. Subsequent functionalization yields access to cationic cyano- and azido-substituted derivatives which represent first examples of a displacement reaction on NHC-stabilized phosphorus(III)-centered cations. The new salts have been fully characterized by NMR spectroscopy and X-ray crystallography.

Herein we report on reactions of "imidazoliumyl-transfer" reagents [L((R/R'))SiMe3][OTf] (4((R/R'))[OTf]); L = imidazolium-2-yl, R/R': Me/Me, (i)Pr/Me, Dipp/H, Dipp/Cl) with pnictogen trichlorides PnCl3 (Pn = P, As, Sb) in various stoichiometries. In the case of the 1:1 reaction of [L((R/R'))SiMe3][OTf] with PCl3 the corresponding cationic imidazoliumyl-substituted dichlorophosphanes [L((R/R'))PCl2](+) (1P((R/R')))(+) are obtained as triflate salts on a multigram scale. We found that the reactions using various stoichiometries of [L((R/R'))SiMe3][OTf] and PnCl3 are less selective in the case of the heavier congeners or by decreasing steric demand of the R-group attached to the N atoms of the heterocycle. An equilibrium between the monocation [L((Me/Me))PCl2](+) (1P((Me/Me)+)), the dication [L((Me/Me))2PCl](2+) (2P((Me/Me)2+)), and the trication [L((Me/Me))3P](3+) (5P((Me/Me)3+)) is observed in solution. Reactions of the monocationic derivatives [L((R/R'))PnCl2][OTf] (Pn = P, As) with Me3SiX (X = CN, N3) resulted in the exchange of the chloro groups for the respective pseudohalogen and yielded the dicyano [L((R/R'))Pn(CN)2][OTf] (6Pn((R/R'))[OTf]) and diazido-substituted pnictanes [L((R/R'))Pn(N3)2][OTf] (7Pn((R/R'))[OTf]), respectively. All new compounds are thoroughly characterized by multinuclear NMR, IR, and Raman spectroscopy. For most cases the molecular structure was confirmed by X-ray crystal structure analysis.

A bridging chloride anion between two electrophilic phosphorus centers was observed for the first time in the molecular structure of the novel P−P bonded cation [L Dipp 2 P 2 Cl 3 ] + (2 + ; L Dipp = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene). Cation 2 + is prepared by the reduction of the monophosphorus species [L Dipp PCl 2 ] + (1 + ) with sodium. DFT calculations, AIM and mechanochemical (compliance constants) analyses are used to examine the bonding situation of this unusual species. The monochloro-substituted cation [L Dipp 2 P 2 Cl] + (3 + ) was likewise observed as a reduction product of 1 + . ■ INTRODUCTIONPhosphorus has the highest homoatomic single bond energy (205 kJ/mol) of any group 15 element and therefore shows a high propensity to form P−P-bonded frameworks. 1 The chemistry of neutral and anionic polyphosphorus compounds has therefore been flourishing for decades. 2 Recently, this area has received fresh impetus from the use of stable N-heterocyclic carbenes (NHCs) for the preparation of P−P-bonded species that display P 2 , P 3 , P 4 , and P 12 frameworks. 3 Several novel types of P−P-bonded phosphorus cations have emerged in recent years. 4 One interesting challenge in this area is the synthesis of cationic polyphosphorus compounds that carry halide substituents. 5 Mono-, di-, and trichlorophosphanylphosphonium ions have been recently described. 6 Chloride substituents have also been incorporated into a few oligophosphonium cations through ion transfer. 7 We recently reported a convenient protocol for the synthesis of cations [L iPr PCl 2 ] + and [L iPr 2 PCl] 2+ (L iPr = 1,3-diisopropylimidazol-2-ylidene), using an imidazolium-transfer reagent [L iPr SiMe 3 ]- [OTf]. 8 The chlorine atoms in these reactive cations can be substituted by cyano and azido groups.Aiming at the synthesis of new polyphosphorus species, we initiated a study of the reaction behavior of our [LPCl 2 ] + cations toward low-valent transition metalates and strong reducing agents. Here, we describe the synthesis of the novel cationic diphosphane derivative [L Dipp 2 P 2 Cl 3 ] + (2 + ; L Dipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and the related cation [L Dipp 2 P 2 Cl] + (3 + ), which are obtained via the reduction of the novel dichloro-substituted cation [L Dipp PCl 2 ] + (1 + ). The molecular structure of cation 2 + shows an unprecedented arrangement where a chloride anion symmetrically bridges two phosphorus centers. The bonding situation in this unusual compound is analyzed by DFT calculations and compliance constant analysis. 9 ■ RESULTS AND DISCUSSION [L Dipp 2 P 2 Cl 3 ][OTf] (2[OTf]) and [L Dipp 2 P 2 Cl][OTf] (3[OTf]) were initially obtained as a product mixture by reacting the triflate salt [L Dipp PCl 2 ][OTf] (1[OTf]) with the recently reported low-valent iron(0) naphthalene complex [K(18-crown-6){Cp*Fe(η 4 -naphthalene)}] (K[Fe]) (Scheme 1). 10 K[Fe] acts as a two-electron reducing agent in this reaction. The cationic complex [Cp*Fe(η 6 -naphthalene)]Cl ([Fe]Cl) was identified as the oxida...

New acceptor-donor-acceptor (A-D-A) oligomers (1 and 2) containing a central dithieno[3,2-b:2',3'-d]pyrrole unit and end-capping thieno[2,3-c]pyrrole-4,6-dione groups have been synthesized and characterized. Bulk heterojunction solar cells were prepared together with PC61BM and PC71BM, and the best results were obtained for the latter acceptor using 1,8-diiodooctane as an additive. Photovoltaic devices containing these oligomers achieved high external quantum efficiencies up to 50%.

The synthesis and optoelectronic properties of novel S,N-heterotetracenes consisting of fused heterocyclic thiophene and pyrrole rings are presented. Tetracyclic and benzannulated derivatives with a varying number and sequence of sulfur and nitrogen heteroatoms were synthesized in multistep synthetic routes. A Buchwald–Hartwig amination of brominated precursors, thermolysis of azide precursors, and a Cadogan reaction of nitro-substituted precursors were successfully applied to eventually build-up pyrrole rings to stable and soluble fused systems. The various obtained heteroatom sequences ‘SSNS’ (SN4), ‘SNNS’ (SN4’’), and ‘NSSN’ (SN4’) allowed for evaluation of structure–property relationships relative to the sulfur analogue tetrathienoacene (‘SSSS’). In line with the results for the whole series of S,N-heteroacenes, we find that replacement of sulfur by nitrogen atoms in the tetra- and hexacyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the opposite effects.