On Haptotropic Rearrangements of Diphosphene and Diarsene Ligands in Titanium Complexes.

Dipnictenes of the type RE=ER (E=P, As, Sb, Bi) are the isovalence electronic heavier analogs of alkenes. Although diphosphenes and dipnictenes in general show a variety of binding modes in metal complexes, little is known about haptotropic shift reactions involving these ligands. Herein, we report an unprecedented η to η rearrangement of the dipnictene ligands in titanocene complexes of the type CpTi(PnAr) (Pn=P, As; Ar=2,4,6-Me-CH, Mes; 2,6-iPr-CH, Dip; 2,4,6-iPr-CH, Tip), initiated by Lewis basic ligands (L=MeCN, PMe, AdNC, CO).

Curved graphene nanoribbons derived from tetrahydropyrene-based polyphenylenes one-pot K-region oxidation and Scholl cyclization.

Precise synthesis of graphene nanoribbons (GNRs) is of great interest to chemists and materials scientists because of their unique opto-electronic properties and potential applications in carbon-based nanoelectronics and spintronics. In addition to the tunable edge structure and width, introducing curvature in GNRs is a powerful structural feature for their chemi-physical property modification. Here, we report an efficient solution synthesis of the first pyrene-based GNR (PyGNR) with curved geometry one-pot K-region oxidation and Scholl cyclization of its corresponding well-soluble tetrahydropyrene-based polyphenylene precursor.

Highly Tunable 4-Phosphoryl Pyrazolone Receptors for Selective Rare-Earth Separation.

Highly selective rare-earth separation has become increasingly important due to the indispensable role of these elements in various cutting-edge technologies including clean energy. However, the similar physicochemical properties of rare-earth elements (REEs) render their separation very challenging, and the development of new selective receptors for these elements is potentially of very considerable economic and environmental importance. Herein, we report the development of a series of 4-phosphoryl pyrazolone receptors for the selective separation of trivalent lanthanum, europium, and ytterbium as the representatives of light, middle, and heavy REEs, respectively.

Direct conversion of white phosphorus to versatile phosphorus transfer reagents via oxidative onioation.

The main feedstock for the value-added phosphorus chemicals used in industry and research is white phosphorus (P), from which the key intermediate for forming P(III) compounds is PCl. Owing to its high reactivity, syntheses based on PCl are often accompanied by product mixtures and laborious work-up procedures, so an alternative process to form a viable P(III) transfer reagent is desirable. Our concept of oxidative onioation, where white phosphorus is selectively converted into triflate salts of versatile P transfer reagents such as [P(L)][OTf] (L is a cationic, N-based substituent; that is, 4-dimethylaminopyridinio), provides a convenient alternative for the implementation of P-O, P-N and P-C bonds while circumventing the use of PCl.

Insights at the molecular level into the formation of oxo-bridged trinuclear uranyl complexes.

Reaction of 1,3,4,6-tetra--acetyl--(2-hydroxy)-naphthylidene glucosamine (HL(Ac)) with uranyl acetate in ethanol leads to formation of dinuclear [(UO)(L)] (1). In a second step 1 is quantitatively transferred into the trinuclear oxo-bridged complex [(UO)(μ-O)(L)] (2) deprotonation and coordination of a water molecule. This transformation was followed by NMR and UV/Vis spectroscopy and it proved possible to selectively introduce O into the μ-bridge.

4-Phosphoryl Pyrazolones for Highly Selective Lithium Separation from Alkali Metal Ions.

Effective receptors for the separation of Li from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, HL -HL , in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process.

Bifunctional Fluorophosphonium Triflates as Intramolecular Frustrated Lewis Pairs: Reversible CO Sequestration and Binding of Carbonyls, Nitriles and Acetylenes.

Electrophilic fluorophosphonium triflates bearing pyridyl (3[OTf]) or imidazolyl (4[OTf])-substituents act as intramolecular frustrated Lewis pairs (FLPs) and reversibly form 1 : 1 adducts with CO (5 and 6 ). An unusual and labile spirocyclic tetrahedral intermediate (7 ) is observed in CO -pressurized (0.5-2.

Polymorphic Phosphorescence from Separable Aggregates with Unique Photophysical Properties.

Platinum complexes aggregate into polymorphs with different intermolecular interactions leading to different photophysical properties. Strong intermolecular interactions stabilize the aggregate to such an extent that the polymorphs can be separated directly by column chromatography. Solid-state structures as well as quantum-chemical calculations confirmed the effect of the interactions on the photophysical properties.

Saccharified Uranyl Ions: Self-Assembly of UO into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases.

The reaction of UO (OAc)  ⋅ 2H O with the biologically inspired ligand 2-salicylidene glucosamine (H L ) results in the formation of the anionic trinuclear uranyl complex [(UO ) (μ -O)(L ) ] (1 ), which was isolated in good yield as its Cs-salt, [Cs] 1. Recrystallization of [Cs] 1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)] 1, which was also obtained for the alkali metal ions Rb and K (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H L ) in a similar procedure with Cs gave the corresponding complex [Cs(18-crown-6)] [(UO ) (μ -O)(L ) ([Cs(18-crown-6)] 2).

Coordination of trivalent lanthanum and cerium, and tetravalent cerium and actinides (An = Th(IV), U(IV), Np(IV)) by a 4-phosphoryl 1-pyrazol-5-olate ligand in solution and the solid state.

Structural investigations of three actinide(iv) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(iv), U(iv), Np(iv)) and their cerium(iv) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(iv) complex shows that dependent on the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(iv) metal centre to bi-capped trigonal prismatic.

Coordination Chemistry and Methylation of Mixed-Substituted Tetraphosphetanes (RP-PtBu) (R=Ph, Py).

Invited for the cover of this issue is the group of Jan J. Weigand at Technische Universität Dresden. The image depicts a puzzle illustrating the coinage metal cations and the methyl group, from which the three-dimensional structure of a multiply methylated tetraphosphetane arises.

Iron-Gallium and Cobalt-Gallium Tetraphosphido Complexes.

The synthesis and characterization of two heterobimetallic complexes [K([18]crown-6){(η-CH)Fe(μ-η:η-P)Ga(nacnac)}] () (CH = anthracene) and [K(dme){(η-CH)Co(μ-η:η-P)Ga(nacnac)}] () with strongly reduced P units is reported. Compounds and are prepared by reaction of the gallium(III) complex [(nacnac)Ga(η-P)] (nacnac = CH[CMeN(2,6-PrCH)]) with bis(anthracene)ferrate(1-) and -cobaltate(1-) salts. The molecular structures of and were determined by X-ray crystallography and feature a P chain which binds to the transition metal atom via all four P atoms and to the gallium atom via the terminal P atoms.

Coordination Chemistry and Methylation of Mixed-Substituted Tetraphosphetanes (RP-PtBu) (R=Ph, Py).

Synthesis of mixed-substituted tetraphosphetanes (RP-PtBu) (R=Ph (4), Py (5); Py=2-pyridyl) is achieved from the condensation of dipyrazolylphosphanes RPpyr (R=Py (1), Ph (3); pyr=3,5-dimethylpyrazolyl) as P -building block (R-P) and tBuPH in an equimolar ratio. Compound 5 is of special interest since the presence of two pyridyl-substituents as well as the P -core allows for a rich coordination chemistry with coinage metal salts [Cu(MeCN) ][OTf], Ag[OTf] and in situ formed [Au(tht)][OTf] (tht=tetrahydrothiophene). Both tetraphosphetanes undergo alkylation reaction with MeOTf to give a series of tetraphosphetanium and tetraphosphetanediium triflate salts with additional methylation of the pyridyl-moiety in case of 5 resulting in interesting novel cyclic trications.

Toward N,P-Doped π-Extended PAHs: A One-Pot Synthesis to Diannulated 1,4,2-Diazaphospholium Triflate Salts.

A novel method for the one-pot synthesis of diannulated 1,4,2-diazaphospholium triflate salts by a MeSiOTf-mediated self-condensation of dichlorophosphaneyl aza-(poly)cyclic aromatic hydrocarbons (aza-(P)AHs; namely, pyridine, quinoline, phenanthridine, and benzo[]thiazole) is reported. The diannulated 1,4,2-diazaphospholium triflate salts are characterized by multinuclear NMR spectroscopy, X-ray analysis, as well as their calculated NICS values, underlining their aromatic character. Quantum mechanical calculations shed light on the intermolecular reaction mechanism.

Controlled scrambling reactions to polyphosphanes bond metathesis reactions.

Triphosphanes R'PP(R)PR' (: R = Py; R = BTz), 1,3-diphenyl-2-pyridyl-triphospholane and pentaphospholanes (RP) (: R = Py; : R = BTz) are obtained in high yield of up to 98% from the reaction of dipyrazolylphosphanes RPpyr (: R = Py; : R = BTz; pyr = 1,3-dimethylpyrazolyl) and the respective secondary phosphane (R'PH, R' = Cy (), Bu (); PhPH(CH)PHPh ()). The formation of derivatives proceeds a condensation reaction while the formation of and can only be explained by a selective scrambling reaction. We realized that the reaction outcome is strongly solvent dependent as outlined by the controlled scrambling reaction pathway towards pentaphospholane .

Helical Nanographenes Containing an Azulene Unit: Synthesis, Crystal Structures, and Properties.

Three unprecedented helical nanographenes (1, 2, and 3) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X-ray crystallographic analysis. The embedded azulene unit in 2 possesses a record-high twisting degree (16.

P-P Condensation and P-N/P-P Bond Metathesis: Facile Synthesis of Cationic Tri- and Tetraphosphanes.

[L P((PhP) C H )][OTf] (4 a,b[OTf]) and [L P(PPh ) ][OTf] (5 b[OTf]) were prepared from the reaction of imidazoliumyl-substituted dipyrazolylphosphane triflate salts [L P(pyr) ][OTf] (3 a,b[OTf]; a: R=Me, b=iPr; L =1,3-dialkyl-4,5-dimethylimidazol-2-yl; pyr=3,5-dimethylpyrazol-1-yl) with the secondary phosphanes PhP(H)C H P(H)Ph) and Ph PH. A stepwise double P-N/P-P bond metathesis to catena-tetraphosphane-2,3-diium triflate salt [(Ph P) (L P) ][OTf] (7 a[OTf] ) is observed when reacting 3 a[OTf] with diphosphane P Ph . The coordination ability of 5 b[OTf] was probed with selected coinage metal salts [Cu(CH CN) ]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene).

Formation of an imidazoliumyl-substituted [(L)P] tetracation and transition metal mediated fragmentation and insertion reaction (L = NHC).

Tetracationic cyclo-tetraphosphane [(L)P] as triflate salt ([OTf]) (L = 4,5-dimethyl-1,3-diisopropyl-imidazol-2-yl) is obtained in high yield from the reduction of [LPCl] ([OTf]) with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine () and represents the first salt of the cationic cyclo-phosphane series with the general formula [L P ] . Theoretical calculations reveal the electrophilic nature of the P atoms within the P-ring due to the influence of the imidazoliumyl-substituents. Further reduction of [OTf] with affords the unexpected formation of the notricyclane P-type cation [(L)P] ([OTf]).

Wave-shaped polycyclic hydrocarbons with controlled aromaticity.

Controlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) and with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of is unambiguously revealed by single-crystal X-ray crystallography analysis.

Construction of alkyl-substituted pentaphosphido ligands in the coordination sphere of cobalt.

Rare mono- and diorganopentaphosphido cobalt complexes are accessible by P-P condensation using the unprecedented, reactive cobalt-gallium tetraphosphido complex [K(dme){(BIAN)Co(μ-η:η-P)Ga(nacnac)}] (). Compound was prepared in good yield by reaction of [K(EtO){(BIAN)Co(η-1,5-cod)}] [, BIAN = bis(mesitylimino)acenaphthene diimine, cod = 1,5-cyclooctadiene] with [Ga(nacnac)(η-P)] (nacnac = CH[CMeN(2,6-iPrCH)]). Reactions with RPCl (R = iPr, Bu, and Cy) selectively afford [(BIAN)Co(-PR)] (), which feature η-coordinated 1,1-diorganopentaphosphido ligands.

Exploration of Thiazolo[5,4-d]thiazole Linkages in Conjugated Porous Organic Polymers for Chemoselective Molecular Sieving.

Porous organic polymers (POPs) have attracted significant attention towards molecular adsorption in recent years due to their high porosity, diverse functionality and excellent chemical stability. In this work, we present a systematic case study on the formation of thiazolo[5,4-d]thiazole (TzTz) linkages through model compounds and its integration to synthesize a set of three novel, thermo-chemically stable TzTz-linked POPs, namely TzTz-POP-3, TzTz-POP-4, and TzTz-POP-5 with triphenylbenzene, tetraphenylpyrene and tetra(hydroxyphenyl)methane cores, respectively. Interestingly, the integrated TzTz moiety of the represented TzTz-POP-3 renders chemoselective removal of organic dye fluorescein (FL) from a mixture with parafuchsine (FU) in aqueous solution.

Toward Full Zigzag-Edged Nanographenes: peri-Tetracene and Its Corresponding Circumanthracene.

Zigzag-edged nanographene with two rows of fused linear acenes, called as n- peri-acene (n-PA), is considered as a potential building unit in the arena of organic electronics. n-PAs with four ( peri-tetracene, 4-PA), five ( peri-pentacene, 5-PA) or more benzene rings in a row have been predicted to show open-shell character, which would be attractive for the development of unprecedented molecular spintronics. However, solution-based synthesis of open-shell n-PA has thus far not been successful because of the poor chemical stability.

Exploration of pyrazine-embedded antiaromatic polycyclic hydrocarbons generated by solution and on-surface azomethine ylide homocoupling.

Nanographenes, namely polycyclic aromatic hydrocarbons (PAHs) with nanoscale dimensions (>1 nm), are atomically precise cutouts from graphene. They represent prime models to enhance the scope of chemical and physical properties of graphene through structural modulation and functionalization. Defined nitrogen doping in nanographenes is particularly attractive due to its potential for increasing the number of π-electrons, with the possibility of introducing localized antiaromatic ring elements.

Cationic Nitrogen-Doped Helical Nanographenes.

Herein, we report the design and synthesis of a series of novel cationic nitrogen-doped nanographenes (CNDNs) with nonplanar geometry and axial chirality. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the frontier orbitals of the CNDNs are energetically lower lying, with a reduced optical energy gap and greater electron-accepting behavior.

Selective Derivatization of a Hexaphosphane from Functionalization of White Phosphorus.

The reaction of LGa (L = Dipp(4-(Dipp-imino)pent-2-en-2-yl)amide; Dipp: 2,6-diisopropylphenyl) and white phosphorus was revisited. A plethora of unprecedented polyphosphanes in addition to the known monoinserted product LGaP (1) are observed. An optimized synthesis of the hitherto unknown hexaphosphane (LGa)P (3) is presented, and its subsequent selective derivatization with Brønsted acids, MeOTf, PhECl (E = P, As), and NaOCP provides access to a wealth of functionalized hexa- and heptaphosphanes.