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A series of phosphorus-arsenic peri-substituted acenaphthene species have been isolated and fully characterised, including single crystal X-ray diffraction. Reactions of EBr3 (E = P, As) with iPr2PAcenapLi (Acenap = acenaphthene-5,6-diyl) afforded the thermally stable peri-substitution supported donor–acceptor complexes, iPr2PAcenapEBr23 and 4. Both complexes show a strong P→E dative interaction, as observed by X-ray crystallography and 31P NMR spectroscopy. DFT calculations indicated the unusual As∙∙∙As contact (3.50 Å) observed in the solid state structure of 4 results from dispersion forces rather than metallic interactions. Incorporation of the excess AsBr3 in the crystal structure of 3 promotes the formation of the ion separated species [iPr2PAcenapAsBr]+Br− 5. A decomposition product 6 containing the rare [As6Br8]2– heterocubane dianion was isolated and characterised crystallographically. The reaction between iPr2PAcenapLi and EtAsI2 afforded tertiary arsine (BrAcenap)2AsEt 7, which was subsequently lithiated and reacted with PhPCl2 and Ph2PCl to afford cyclic PhP(Acenap)2AsEt 8 and acyclic EtAs(AcenapPPh2)2 9.

We would like to thank the ERC (EU FP7 Consolidator Grant 614290 “EXONMR”) and EPSRC for computational support through the Collaborative Computational Project on NMR Crystallography (CCP-NC), via EP/M022501/1 and EP/J010510/1. SEA would like to thank the Royal Society and the Wolfson Foundation for a merit award. The research data (and/or materials) supporting this publication can be accessed at DOI: 10.17630/d0b365a1-b647-4556-b6f8-24d99d0c7a8a. A series of P−E‐containing heterocycles (E=chalcogen) with aromatic backbones were synthesised and characterised by single‐crystal and powder XRD, microanalysis and mass spectrometry. Solution‐ and solid‐state 31P and 77Se NMR spectroscopy revealed significant differences between the NMR parameters in solution and in the solid state, related to conformational changes in the molecules. Many compounds were shown to exhibit a number of different polymorphic structures (identified by single‐crystal XRD), although the bulk material studied by solid‐state NMR spectroscopy often contained just one major polymorph. For the unoxidised heterocycles, the presence of weak intermolecular J couplings was also investigated by DFT calculations. Publisher PDF

All 21 [n]-azacubanes are proposed by theoreticians to be stable, however, to-date only the synthesis of 1,4-diazacubane has been reported - as a Ni2+ templated Kagome metal organic framework (MOF). Described herein is the structural reassignment of this Kagome MOF on the basis of deducing the precise experimental procedure, and demonstrating that rather than the formation of 1,4-diazacubane, charge is balanced by disordered piperazinium cations across a twelve-fold symmetry site. Furthermore, quantum chemical calculations reveal that 1,4-diazacubane is unlikely to form under the reported conditions due to unfavorable enthalpies for select hypothetical reactions leading to such a product. This significant structure correction upholds the unconquered synthesis status quo of azacubane.

A mononuclear iron(II) complex that displays a gradual two-step spin-crossover (SCO) transition is reported. The intermediate plateau (IP) occurs between HS0.40LS0.60 and HS0.30LS0.70 (HS = high spin; LS = low spin) ratios over the region of ca. 190–170 K. A phase change occurs at the IP, breaking the symmetry, resulting in six independent SCO sites compared to one at the 100% HS and LS plateau regions, respectively. Variable-temperature X-ray photoelectron spectroscopy shows that the SCO behavior is completely reversible among the HS, IP, and LS regions. The results both confirm and extend the related results for the above system described by Halcrow et al. (KulmaczewskiR.; CespedesO.; HalcrowM. A.Gradual Thermal Spin-Crossover Mediated By a Reentrant Z′ = 1 → Z′ = 6 → Z′ = 1 Phase Transition, Inorg. Chem. 2017, 56, 3144−314828244751) in a recent report.

A series of new selenium-containing heteroatom compounds were synthesized in good yields by the reactions of Woollins’ reagent with various organic substrates such as cyclohexanamine, N-benzoylbenzamide, benzoic anhydride, 4-fluoro-N-(2-oxo-2-phenylethyl)benzamide, N-benzoylbenzamide, benzoic anhydride, 3-(bromomethyl)benzonitrile, 1,2-diphenylethane-1,2-diol and sodium alcoholate. Three representative X-ray structures are described. Postprint Postprint

Correction for ‘Straightening out halogen bonds’ by Caitlin J. Setter et al., CrystEngComm, 2020, 22, 1687–1690, DOI: 10.1039/D0CE00176G.

We gratefully acknowledge funding support from The Leverhulme Trust (RPG-2013-343) and EPSRC (EP/K005499/1). The ionothermal synthesis, structure, and magnetic susceptibility of a novel inorganic–organic hybrid material, imidazolium vanadium(III,IV) oxyfluoride [C3H5N2][V9O6F24(H2O)2] (ImVOF) are presented. The structure consists of inorganic vanadium oxyfluoride slabs with kagome layers of V4+ S = 1/2 equation image ions separated by a mixed valence layer. These inorganic slabs are intercalated with imidazolium cations. Quinuclidinium (Q) and pyrazinium (Pyz) cations can also be incorporated into the hybrid structure type to give QVOF and PyzVOF analogues, respectively. The highly frustrated topology of the inorganic slabs, along with the quantum nature of the magnetism associated with V4+, means that these materials are excellent candidates to host exotic magnetic ground states, such as the highly sought quantum spin liquid. Magnetic susceptibility measurements of all samples suggest an absence of conventional long-range magnetic order down to 2 K despite considerable antiferromagnetic exchange. Postprint Postprint

The ionothermal synthesis, structure, and magnetic susceptibility of a novel inorganic-organic hybrid material, imidazolium vanadium(III,IV) oxyfluoride [CHN][VOF(HO)] (ImVOF) are presented. The structure consists of inorganic vanadium oxyfluoride slabs with kagome layers of V S=${{ 1/2 }}$ ions separated by a mixed valence layer. These inorganic slabs are intercalated with imidazolium cations. Quinuclidinium (Q) and pyrazinium (Pyz) cations can also be incorporated into the hybrid structure type to give QVOF and PyzVOF analogues, respectively. The highly frustrated topology of the inorganic slabs, along with the quantum nature of the magnetism associated with V, means that these materials are excellent candidates to host exotic magnetic ground states, such as the highly sought quantum spin liquid. Magnetic susceptibility measurements of all samples suggest an absence of conventional long-range magnetic order down to 2 K despite considerable antiferromagnetic exchange. All in a spin: Antiferromagnetic crystalline solids with a kagome network of ions are desired as realizations of two-dimensional quantum spin liquids. Until recently, the few examples of these materials were all based on Cu ions. Now, the ionothermal synthesis, structure, and magnetic properties of a family of inorganic-organic hybrid solids that contain antiferromagnetic kagome layers of V ions is presented.

The authors gratefully acknowledge the Royal Society (University Research Fellowship to CSJC) and the DOE (DE-FG02-13ER16370) for financial support. The synthesis and characterization of abnormal N-heterocyclic carbene, cyclic (alkyl)(amino)carbene, and mesoionic carbene copper(I) complexes are reported. These organometallic species are obtained via a versatile and inexpensive synthetic pathway using readily available reactants, namely copper oxide and iminium salts. The catalytic activity of this series of complexes was evaluated in the [3+2] cycloaddition of alkynes with azides (CuAAC). Outstanding catalytic properties were observed for the abnormal NHC- and triazolylidene-based copper(I) complexes. Postprint

The authors are grateful to EPSRC for financial support (EP/J010510/1, EP/J501542/1, EP/F018096/1) and the award of a studentship. Solid-state NMR spectra of new P–Se heterocycles based on peri-substituted naphthalene motifs show the presence of unusual J couplings between Se and P. These couplings are between atoms in adjacent molecules and occur “through space”, rather than through conventional covalent bonds. Experimental measurements are supported by relativistic DFT calculations, which confirm the presence of couplings between nonbonded atoms, and provide information on the pathway of the interaction. This observation improves the understanding of J couplings and offers insight into the factors that affect crystal packing in solids, for future synthetic exploitation. Postprint

The authors are thankful to the EPSRC, the EPSRC National Mass Spectrometry Service Centre (NMSSC) Swansea, the School of Chemistry St. Andrews, and EaStCHEM for support. A series of peri-substituted phosphorus-tellurium systems R’Te–Acenap–PR2 (R’ = Ph, p-An, Nap, Mes, Tip; R = iPr, Ph) exhibiting large “through space” spin-spin coupling constants and the “onset” of three-centre four-electron type interactions are presented. The influence of the substituents at the phosphorus and tellurium atoms as well as their behavior upon oxidation (with S, Se) or metal-coordination (Pt, Au) is discussed using NMR spectroscopy, single crystal X-ray diffraction, and advanced DFT studies including NBO, AIM and ELI-D analyses. Postprint

The synthesis of a range of rhodium(III) and iridium(III) half sandwich complexes with aryl dithiolato ligands of varying geometry and flexibility is reported. These include dinuclear [Cp*M(S‒R‒S)]2 complexes 3b and 4b, M = Rh, Ir; S‒R‒S = naphthalene-1,8-dithiolate (b) and four dinuclear complexes bearing bridging dithiolate ligands [(Cp*M)2(μ2-Cl)(μ2-S‒R‒S)]Cl 3c, 4c, 5b, 6b, M = Rh, Ir; S‒R‒S = naphthalene-1,8-dithiolate (b) or acenaphthene-5,6-dithiolate (c). The introduction of a less rigid biphenyl dithiolate backbone resulted in the tetranuclear dicationic complex [(Cp*Rh)4(S-R-S)3]Cl2 (3d), S‒R‒S = biphenyl-2,2’-dithiolate (d) with dithiolate ligands in two different bridging modes. All new complexes were fully characterised by multinuclear NMR, IR, Raman and MS spectroscopy and single crystal X-ray diffraction. Postprint Postprint

The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC). M.B. wishes to thank EaStCHEM and the University of St Andrews for support. Three related series of peri‐substituted bis(tellurides) bearing naphthalene, acenaphthene and acenaphthylene backbones (Nap/Acenap/Aceyl(TeY)2 (Nap=naphthalene‐1,8‐diyl N ; Acenap=acenaphthene‐5,6‐diyl A ; Aceyl=acenaphthylene‐5,6‐diyl Ay ; Y=Ph 1 ; Fp 2 ; Tol 3 ; An‐p­ 4 ; An‐o­ 5 ; Tp 6 ; Mes 7 ; Tip 8 ) have been synthesised and their solid‐state structures determined by X‐ray crystallography. Molecular conformations were classified as a function of the two C9‐C‐Te‐C(Y) dihedral angles (θ); in the solid all members adopt AB or CCt configurations, with larger Te(aryl) moieties exclusively imposing the CCt variant. Exceptionally large J(125Te,125Te) spin–spin coupling constants between 3289–3848 Hz were obtained for compounds substituted by bulky Te(aryl) groups, implying these species are locked in a CCt‐type conformation. In contrast, compounds incorporating smaller Te(aryl) moieties are predicted to be rather dynamic in solution and afford much smaller J values (2050–2676 Hz), characteristic of greater populations of AB conformers with lower couplings. This conformational dependence of through‐space coupling is supported by DFT calculations. Postprint

The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC), EaStCHEM and the University of St Andrews. A group of sterically encumbered peri-substituted acenaphthenes have been prepared, containing tin moieties at the 5,6-positions in 1 – 3 ([Acenap(SnR3)2], Acenap = acenaphthene-5,6-diyl; R3 = Ph3 ( 1 ), Me3 ( 2 ); [(Acenap)2(SnMe2)2] ( 3 )) and phosphorus functional groups at the proximal peri-positions in 4 and 5 ([Acenap(PR2)(PiPr2)] R2 = Ph2 ( 4 ), Ph(iPr) ( 5 )). Bis(stannane) structures 1 – 3 are dominated by repulsive interactions between the bulky tin groups, leading to peri-distances approaching the sum of van der Waals radii. Conversely, the quasi-linear CPh-P···P three-body fragments found in bis(phosphine) 4 suggest the presence of a lp(P)−σ*(P–C) donor–acceptor 3c-4e type interaction, supported by a notably short intramolecular P···P distance and notably large JPP through-space coupling (180 Hz). Severely strained bis(sulfides) 4-S and 5-S , experiencing pronounced in-plane and out-of-plane displacements of the exocyclic peri-bonds, have also been isolated following treatment of 4 and 5 with sulfur. The resulting nonbonded intramolecular P···P distances, ∼4.05 Å and ∼12% longer than twice the van der Waals radii of P (3.60 Å), are among the largest ever reported peri-separations, independent of the heteroatoms involved, and comparable to the distance found in 1 containing the larger Sn atoms (4.07 Å). In addition we report two metal complexes with square planar [( 4 )PtCl2] ( 4-Pt ) and octahedral cis-[( 4 )Mo(CO)4] ( 4-Mo ) geometries. In both complexes the bis(phosphine) backbone is distorted, but notably less so than in bis(sulfide) 4-S . All compounds were fully characterized, and except for bis(phosphine) 5 , crystal structures were determined. Postprint Postprint

This work is supported by funding from the EPSRC UK A series of peri-substituted acenaphthylenes that contain mixed halogen-chalcogen functionalities at the 5,6-positions in 1-6 [Acenapyl[X](EPh) (Acenapyl = acenaphthylene-5,6-diyl; X = Br, I; E = S, Se, Te)] and chalcogen-chalcogen moieties in 7-11 [Acenap(EPh)(EPh) (Acenap = acenaphthene-5,6-diyl; E/E = S, Se, Te)] have been prepared from their corresponding acenaphthene analogues A1-A11 by utilising 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) for the dehydrogenation of the ethane backbone. The related dihalide compounds 13 and 14 Acenapyl[XX] (XX = BrBr, II) have also been prepared by following a similar procedure, and 1,2,5,6-tetrabromo-1,2-dihydroacenaphthylene A0 was prepared as an intermediate by following an alternative route to 13. The series of acenaphthylene compounds have remarkably similar molecular structures to their acenaphthene counterparts; they exhibit an expected increase in peri separation as heavier congeners occupy the close peri positions. The presence of the ethene bridge, however, naturally compresses the nearest bay angle as it increases the splay of the exocyclic peri atoms, thereby resulting in a minor increase in separation relative to equivalent acenaphthenes. The structures of 1-11, 13 and 14 are discussed and compared with previously reported analogous naphthalene and acenaphthene compounds. Similar to acenaphthene derivatives, aromatic ring conformations and the location of p-type lone pairs influences the geometry of the peri region. Under appropriate geometric conditions, quasi-linear three-body C-Ph-EZ (E = Te, Se, S; Z = Br/E) fragments provide an attractive component for the EZ interaction. DFT studies confirm the onset of formation of three-center, four-electron bonding, similar in extent to that observed in analogous acenaphthenes, despite an increase in the peri distances. Postprint

Reaction of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (Woollins' reagent) with four equivalents of primary/secondary amines led to a series of ammonium phenylphosphonamido-diselenoates or phenylphosphonamido- diselenoic diamides 1a-n, the latter further reacted in situ with either two equivalents of haloalkanes or an equimolar amount of dihaloalkane, resulting in formation of the corresponding Se-alkylphenyl-Se-alkylphenyl- phosphonamidodiselenoates 2a-n and alkane bis(N-alkyl-P-phenylphosphonamido- diselenoate) derivatives 3a-n in good to excellent yields. All new compounds have been characterized spectroscopically including multinuclear NMR ( H, C, P and Se), IR and mass spectroscopy. Two representative X-ray structures are also described. Woollins' reagent has been applied as a highly efficient building block for the synthesis of organo selenium-phosphorus heteroatom compounds.

This work was financially supported by the Engineering and Physical Sciences Research Council (EPSRC) and by COST action (grant CM1302, SIPs). A new synthetic route to FcPH2 and FcPCl2 (Fc = Ferrocenyl) is presented. This method avoids the challenging monolithiation of ferrocene, as well as any tedious purification steps. All reactions are high yielding and easily conducted on a relatively large scale, using economical and commercially available synthetic precursors. Postprint Postprint

This work was financially supported by the EPSRC and COST actions CM0802 PhoSciNet and CM1302 SIPs. A series of phosphine–stibine and phosphine–stiborane peri–substituted acenaphthenes containing all permutations of pentavalent groups –SbClnPh4-n (5–9), as well as trivalent groups –SbCl2, –Sb(R)Cl, and –SbPh2 (2–4, R = Ph, Mes), were synthesised and fully characterised including single crystal diffraction and multinuclear NMR. In addition, the bonding in these species was studied by DFT computational methods. The P–Sb dative interactions in both series range from strongly bonding to non-bonding as the Lewis acidity of the Sb acceptor is decreased. In the pentavalent antimony series, a significant change in the P–Sb distance is observed between –SbClPh3 and –SbCl2Ph2 derivatives 6 and 7, consistent with a change from a bonding to a non-bonding interaction in a response to relatively small change in Lewis acidity of the acceptor. In the SbIII series, two geometric forms are observed. The P–Sb bond length in the SbCl2 derivative 2 is as expected for a normal (rather than a dative) bond. Rather unexpectedly, the phosphine–stiborane complexes 5–9 represent the first examples of σ4P→σ6Sb structural motif. Postprint

The authors are grateful to the EPSRC, the EPSRC National Mass Spectrometry Service Centre (NMSSC) Swansea, the School of Chemistry St. Andrews, EaStCHEM, and NSERC Canada for financial support. A comprehensive investigation of reactions of alkali-metal derivatives of the ditelluro dianion [TePV(NtBu)(μ-NtBu)]22– (L2–, E = Te) with p-block element halides produced a series of novel heterocycles incorporating P2VN2 rings, tellurium, and group 13–16 elements. The dianion engages in Te,Te′-chelation to the metal center in Ph2Ge and R2Sn (R = tBu, nBu, Ph) derivatives; similar behavior was noted for group 14 derivatives of L2– (E = S, Se). In the case of group 13 trihalides MCl3 (M = Ga, In), neutral spirocyclic complexes (L)M[NtBu(Te)PV(μ-NtBu)2PIIIN(H)tBu)] (M = Ga, In) comprised of a Te,Te′-chelated ligand L2– and a N,Te-bonded ligand resulting from loss of Te and monoprotonation were obtained. In reactions with RPCl2 (R = tBu, Ad, iPr2N) a significant difference was observed between Se- and S-containing systems. In the former case, Se,Se′-chelated derivatives were formed in high yields, whereas the N,S-chelated isomers predominated for sulfur. All complexes were characterized by multinuclear (1H, 31P, 77Se, 119Sn, and 125Te) NMR spectroscopy; this technique was especially useful in the analysis of the mixture of (L)(Se) and (L)(SeSe) obtained from the reaction of Se2Cl2 with L2– (E = Te). Single-crystal X-ray structures were obtained for the spirocyclic In complex (9), (L)GePh2 (E = Te, 10), (L)SntBu2 (E = Te, 12a); E = Se, 12aSe, E = S, 12aS) and (L)(μ-SeSe) (E = Te, 16). Postprint Postprint

Financial support from the EPSRC and NSERC (Canada) is acknowledged. Metathetical reactions of alkali–metal derivatives of the dianion [tBuN(Se)P(μ-NtBu)2P(Se)NtBu]2− (2Se2−) with Ag(NHC)Cl, Ag[BF4], AuCl(THT) and HgCl2, as well as the reaction of 2S2− with AuCl(THT) were investigated. The observed products all incorporate the monoprotonated ligands 2SeH− or 2SH− in a variety of structural arrangements around the metal centres, including tetrameric and trimeric macrocycles [Ag and Au (E = Se)], a ladder (Au, E = S) and a spirocycle (Hg); the ladder contains both the dianion 2S2− and the monoanion 2SH− as ligands linking three Au2 units. All complexes have been characterised in the solid state by single crystal X-ray analyses and in solution by multinuclear (1H, 31P and 77Se) NMR spectra. Postprint

The authors thank EPSRC and NSERC (Canada) for financial support. Reactions of the dianion [Te(tBuN)P(μ-NtBu)2P(NtBu)Te]2− with I2 or [Cp*RhCl2]2 unexpectedly produced complexes of the novel spirocyclic Te5 dianion [{tBuN(Te)P(μ-NtBu)2P(Te)NtBu}2μ-Te]2−, which is N,N′-coordinated to two Na+ ions in the disodium derivative and adopts a Te,Te′,Te′′-bonding mode in the Cp*Rh complex. Postprint

A number of four-component condensation adducts, which were readily obtained from one-pot reaction of aryl carboxylic acids, arylaldehydes, arylamines and c-hexylisocyanide, were treated with two equivalents of Woollins’ reagent leading to the formation of a series of novel selenoamides with one or two C=Se groups, or heterocyclic compounds such as 1,3-selenazole and 1,3-selenazolidin-5-one Postprint

The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC) and EaStCHEM. A series of sterically encumbered peri-substituted acenaphthenes have been prepared containing chalcogen and tin moieties at the close 5,6-positions (Acenap[SnPh3][ER], Acenap = acenaphthene-5,6-diyl, ER = SPh (1), SePh (2), TePh (3), SEt (4); Acenap[SnPh2Cl][EPh], E = S (5), Se (6); Acenap[SnBu2Cl][ER], ER = SPh(7), SePh (8), SEt (9)). Two geminally bis(peri-substituted) derivatives ({Acenap[SPh2]}2SnX2, X = Cl (10), Ph (11)) have also been prepared, along with the bromo–sulfur derivative Acenap(Br)(SEt) (15). All 11 chalcogen–tin compounds align a Sn–CPh/Sn–Cl bond along the mean acenaphthene plane and position a chalcogen lone pair in close proximity to the electropositive tin center, promoting the formation of a weakly attractive intramolecular donor–acceptor E···Sn–CPh/E···Sn–Cl 3c-4e type interaction. The extent of E→Sn bonding was investigated by X-ray crystallography and solution-state NMR and was found to be more prevalent in triorganotin chlorides 5–9 in comparison with triphenyltin derivatives 1–4. The increased Lewis acidity of the tin center resulting from coordination of a highly electronegative chlorine atom was found to greatly enhance the lp(E)−σ*(Sn–Y) donor–acceptor 3c-4e type interaction, with substantially shorter E–Sn peri distances observed in the solid state for triorganotin chlorides 5–9 (∼75% ∑rvdW) and significant 1J(119Sn,77Se) spin–spin coupling constants (SSCCs) observed for 6 (163 Hz) and 8 (143 Hz) in comparison to that for the triphenyltin derivative 2 (68 Hz). Similar observations were observed for geminally bis(peri-substituted) derivatives 10 and 11. Postprint

S.V. is supported by an EPSRC Doctoral Training Grant; B.E.B. acknowledges an EaStCHEM Hirst Academic Fellowship by the School of Chemistry, St Andrews and funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (REA 334496) The synthesis of rigid symmetric polyradical model systems with inter-spin distances between 1.4 and 4 nm and their room temperature continuous wave (CW) EPR spectra are reported. Conditions for attachment of the spin-label via esterification have been optimized on the direct synthesis of polyradicals from commercially available polyphenols and the carboxylic acid functionalized nitroxide TPC. A common synthetic protocol utilizing 4-hydroxy-4′-iodobiphenyl as a key building block has been used to synthesize an equilateral biradical and a triradical in only two steps from commercially available starting materials. The first synthesis of a tetraradical based upon an adamantane core bearing six equivalent nitroxide–nitroxide distances is also reported. These systems are very promising candidates for studying multi-spin effects in pulsed EPR distance measurements. Publisher PDF

The authors thank the EaStChem, EPSRC, and the COST actions CM0802 PhoSciNet and CM1302 SIPs for financial support. The reactions of peri-substitution-stabilized phosphanylidene-phosphorane 1 with [AuCl(tht)] or [PtCl2(cod)] afford binuclear complexes [((1)(AuCl)2)2] 2 and [((1)(PtCl2))2] 3, in which four electrons of the ligand are used in bonding to two metal atoms in the bridging arrangement. Reactions of 1 with [Mo(CO)4(nbd)] or (RhCl2Cp*)2 afford mononuclear complexes [(1)2Mo(CO)4] 4 and [(1)RhCl2Cp*] 5, in which two electrons of the ligand are used to form terminal complexes. Formation of these complexes disrupts the negative hyperconjugation at the P–P bond to various extents, which is mirrored by variations in their P–P bond distances (2.179(4)–2.246(4) Å). The P–P bond is ruptured upon formation of Pd diphosphene complex 6, which is likely to proceed through a phosphinidene intermediate. In air, 1 is fully oxidized to phosphonic acid 7. Reactions of 1 with chalcogens under mild conditions generally afford mixtures of products, from which the trithionated 8, dithionated 9, diselenated 10, and monotellurated 11 species were isolated. The bonding in the chalcogeno derivatives is discussed using DFT (B3LYP) and natural bond orbital analysis, which indicate a contribution from dative bonding in 8–10. The buttressing effect of the peri backbone is shown to be an essential factor in the formation of the single push–double-pull bis(borane) 13. This is demonstrated experimentally through a synthesis parallel to that used to make 13, but lacking the backbone, which leads to different products. The P–P bond distances in the reported products, as well as additional species, are correlated with Wiberg bond indices, showing very good agreement for a variety of bonding modes, including the negative hyperconjugation. Postprint Postprint

Funding: Engineering and Physical Sciences Research Council (EPSRC) Four related sterically restricted pen-substituted acenaphthenes have been prepared containing mixed tin phosphorus moieties in the proximal 5,6-positions (Acenap[SnR3][(PPr2)-Pr-i]; Acenap = acenaphthene-5,6-diyl; R-3 = Ph-3 (1), Ph2Cl (2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P-Sn bonding within the series was investigated by X-ray crystallography, solution and solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM) calculations. All members of the series adopt a conformation such that the phosphorus lone pair is located directly opposite the tin center, promoting an intramolecular donor acceptor P -> Sn type interaction. The extent of covalent bonding between Sn and P is found to be much greater in triorganotin chlorides 2-4 in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atom naturally increases the Lewis acidity of the tin center, enhancing the Ip(P)-sigma*(Sn-Y) donor acceptor 3c-4e type interaction, as indicated by conspicuously short Sn-P peri distances and significant (1)J(P-31,Sn-119) spin spin coupling constants (SSCCs) in the range 740-754 Hz. Evidence supporting the presence of this interaction was also found in solid-state NMR spectra of some of the compounds which exhibit an indirect spin spin coupling on the same order of magnitude as observed in solution. DFT calculations confirm the increased covalent bonding between P and Sn in 2-4, with notable WBIs of ca. 0.35 obtained, in comparison to 0.1 in 1. Postprint

The authors are thankful to the School of Chemistry and EaStCHEM for support. Woollins' reagent (WR, (PhPSe2)2) plays an essential role in the selenation of organic compounds. Reaction of WR with pyridine gives the P(V) species PhPSe2 stabilised by pyridine coordination which is the first crystallographically characterised mononuclear RPSe2 system stabilised by an external molecule and has potential as a selenation reagent for reactions under mild conditions. Publisher PDF

This work was made open access through funds from the RCUK open access block grant. A proximate Lewis basic group facilitates the mild dehydrogenative P–As intramolecular coupling in the phosphine-arsine peri-substituted acenaphthene 3 , affording thermally and hydrolytically stable arsanylidine-phosphorane 4 with a sterically accessible two-coordinate arsenic atom. The formation of 4 is thermoneutral due to the dehydrogenation being concerted with the donor coordination. Reaction of 4 with a limited amount of oxygen reveals arsinidene-like reactivity via formation of cyclooligoarsines, supporting the formulation of the bonding in 4 as base-stabilized arsinidene R3P→AsR. Publisher PDF

There are only limited reports on vanadium(IV) oxyfluorides (VOFs) with extended crystal structures. Here we expand and enrich the list of existing VOFs with a series of 14 new materials "VOF-n (n = 1-14)" prepared using ionothermal and solvothermal synthesis methods. All of these materials arise from the condensation of a dimeric structural motif. These VOFs can be classified into three groups depending on their key structural features; layer structures: VOF-1 "[HN2C7H6][V2O2F5]", VOF-2 "[HN2C4H4][V2O2F5]", VOF-3 "[HN2C3H4][V2O2F5]" and VOF-4 "V-2(N2C4H4)O2F4", ladder like structures: VOF-5 "[NH4(HN2C3H4)][V2O2F6]", VOF-6 "[K(HN2C3H4)][V2O2F6]", VOF-7 "[HNH2CH2CH3][VOF3]", VOF-8 "[HN2C7H6][VOF3]", VOF-9 "[H2N2C4H6][V2O2F6]", VOF-10 "beta-RbVOF3", VOF-11 "alpha-KVOF3", VOF-12 "beta-KVOF3", VOF-13 "[H-2(NH2)(2)(CH2)(2)][V2O2F6]", and a chain structure: VOF-14 "[H2N2C6H12][V2O2F7]". The crystal structures of VOF-n are presented, and their synthetic and structural relationships are discussed. Postprint

The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC). M.B. wishes to thank EaStCHEM and the University of St. Andrews for support. Twelve related monocation chalconium salts [{Nap(EPh)(E'Ph)Me}(+){CF3SO3}(-)] 2-4, [{Acenap(Br)(EPh)Me}{CF3SO3}(-)] 5-7, and [{Acenap(EPh)(E'Ph)Me}(+){CF3SO3}(-)] 8-13 have been prepared and structurally characterized. For their synthesis naphthalene compounds [Nap(EPh)(E'Ph)] (Nap = naphthalene-1,8-diyl; E/E' = S, Se, Te) N2-N4 and associated acenaphthene derivatives [Acenap(X)(EPh)]/[Acenap(EPh)(E'Ph)] (Acenap = acenaphthene-5,6-diyl; E/E' = S, Se, Te; X = Br) A5-A13 were independently treated with a single molar equivalent of methyl trifluoromethanesulfonate (MeOTf). In addition, reaction of bis-tellurium compound A10 with 2 equiv of MeOTf afforded the doubly methylated dication salt [{Acenap(TePhMe)(2)}(2+){(CF3SO3)(2)}(2-)}] 14. The distortion of the rigid naphthalene and acenaphthene backbone away from ideal was investigated in each case and correlated in general with the steric bulk of the interacting atoms located at the proximal peri positions. Naturally, introduction of the ethane linker in acenaphthene compounds increased the splay of the bay region compared with equivalent naphthalene derivatives resulting in greater peri distances. The conformation of the aromatic rings and subsequent location of p-type lone pairs has a significant impact on the geometry of the peri region, with anomalies in peri separations correlated to the ability of the frontier orbitals to take part in attractive or repulsive interactions. In all but one of the monocations a quasi-linear three-body C-Me-E center dot center dot center dot Z (E = Te, Se, S; Z = Br/E) fragment provides an attractive component for the E center dot center dot center dot Z interaction. Density functional studies confirmed these interactions and suggested the onset of formation of three-center, four-electron bonding under appropriate geometric conditions, becoming more prevalent as heavier congeners are introduced along the series, The increasingly large J values for Se-Se, Te-Se, and Te-Te coupling observed in the Se-77 and Te-125 NMR spectra for 1, 3, 4, 9, 10, and 13 give further evidence for the existence of a weakly attractive through-space interaction. Postprint