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Sterically restricted tin phosphines, stabilized by weak intramolecular donor-acceptor interactions

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.PostprintPeer reviewe

Bridging (thionylimido)metal complexes

L.J.R.M. is grateful to EPSRC for a provision of Ph.D. funding. M.B. thanks the School of Chemistry and EaStCHEM for support.We report the first examples of the thionylimido ligand acting as a μ2-bridging ligand between two transition-metal centers; using Cp2Ti(NSO)2, we describe bi- and tetrametallic systems.Publisher PDFPeer reviewe

Rhodium(III) and iridium(III) half-sandwich complexes with tertiary arsine and stibine ligands

This work was financially supported by the EPSRC and the EPSRC National Mass Spectrometry Service Centre (NMSSC) Swansea.The syntheses of rhodium(III) and iridium(III) half sandwich complexes containing tertiary arsine and stibine ligands of the form [Cp*M(L)Cl2] (M = Rh, Ir; L = AsEt3, AsPh3, SbPh3) are reported. These compounds represent infrequent examples of rhodium and iridium metal complexes bearing arsenic or antimony ligands. All new compounds were fully characterised using 1H and 13C NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction. DFT calculations show the formation of the complexes from (Cp*MCl2)2 and EPh3 (E = P, As, Sb) to be highly exothermic, although the enthalpic driving force is decreasing in the expected sequence P > As > Sb.PostprintPeer reviewe

Reactivity profile of a peri-substitution-stabilized phosphanylidene-phosphorane : synthetic, structural, and computational studies

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.PostprintPostprintPeer reviewe

Thionylimido complexes

An improved route to d-block and main group NSO complexes is presented including the synthesis of the first antimony(V) complexes, (Ar3Sb(NSO)2), and copper examples (CuBipy(PPh3)NSO). The structures of eight complexes are reported. The observed variation in M-N-S bond angles is due to the combination of orbital overlap (ligand-to-metal bonding) and the degree of ionicity of the bonding.Publisher PDFPeer reviewe

Phosphorus‒bismuth peri-substituted acenaphthenes : a synthetic, structural and computational study

This work was financially supported by the Engineering and Physical Sciences Research Council (EPSRC). This included PhD studentship to TEC (Centre for Doctoral Training in Critical Resource Catalysis (CRITICAT), Grant code: EP/L016419/1) and to PN (Grant code EP/L505079/1). The authors would like to thank COST action SM1302 SIPs; the EPSRC UK National Mass Spectrometry Facility at Swansea University for the acquisition and processing of Mass Spectrometry Data and to EaStCHEM and the School of Chemistry for support.A series of acenaphthene species with a diisopropylphosphino group and a variety of bismuth functionalities in the peri-positions were synthesised and fully characterised, including single crystal X–ray diffraction. The majority of the reported species feature a relatively rare interpnictogen P−Bi bond. The series includes the phosphine¬−bismuthine, Acenap(PiPr2)(BiPh2) 2 (Acenap = acenaphthene-5,6-diyl), which was subjected to a fluorodearylation reaction to produce Acenap(PiPr2)(BiPhX) 5−8 and 10 (X = BF4-, Cl, Br, I, SPh), displaying varying degrees of ionicity. The geminally bis(acenaphthyl) substituted [Acenap(PiPr2)2]BiPh 3 shows a large through-space coupling of 17.8 Hz, formally 8TSJPP. Coupling deformation density (CDD) calculations confirm the double through-space coupling pathway, in which the P and Bi lone pairs mediate communication between the two 31P nuclei. Several synthetic routes towards the phosphine−diiodobismuthine Acenap(PiPr2)(BiI2) 9 have been investigated, however the purity of this, surprisingly thermally stable potential synthon, remains poor.PostprintPostprintPeer reviewe

Strategia graduale integrata in undici fasi: un approccio mimetico al processo di trasferimento nella didattica della traduzione

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.PostprintPeer reviewe

Ligand electronic fine-tuning and its repercussion on the photocatalytic activity and mechanistic pathways of the copper-photocatalysed aza-Henry Reaction

C.Li thanks the Prof. & Mrs Purdie Bequests Scholarship and AstraZeneca PhD Studentship.A family of six structurally related heteroleptic copper(I) complexes of the form of [Cu(N^N)(P^P)]+ bearing a 2,9-dimethyl-1,10-phenanthroline diimine (N^N) ligand and a series of electronically tunable xantphos (P^P) ligands have been synthesized and their optoelectronic properties characterized. The reactivity of these complexes in the copper-photocatalyzed Aza-Henry reaction of N-Phenyltetrahydroisoquinoline was evaluated, while the related excited state kinetics were comprehensively studied. By subtlety changing the electron-donating properties of the P^P ligands with neglegible structural differences, we could tailor the photoredox properties and relate it to their reactivity. Moreover, depending on the exited-state redox potential of the catalysts, the preferred mechanism can shift between reductive quenching, energy transfer and oxidative quenching pathways. A combined study of structural modulation of copper(I) photocatalysts, optoelectronic properties and photocatalytic reactivity resulted in a clearer understanding of both the rational design of the photocatalyst and the complexity of competing photoinduced electron and energy transfer mechanisms.Publisher PDFPeer reviewe

OSCA: a comprehensive open-access system of analysis of posterior capsular opacification

BACKGROUND: This paper presents and tests a comprehensive computerised system of analysis of digital images of posterior capsule opacification (PCO). It updates and expands significantly on a previous presentation to include facilities for selecting user defined central areas and for registering and subsequent merging of images for artefact removal. Also, the program is compiled and thus eliminates the need for specialised additional software. The system is referred to in this paper as the open-access systematic capsule assessment (OSCA). The system is designed to be evidence based, objective and openly available, improving on current systems of analysis. METHODS: Principal features of the OSCA system of analysis are discussed. Flash artefacts are automatically located in two PCO images and the images merged to produce a composite free from these artefacts. For this to be possible the second image has to be manipulated with a registration technique to bring it into alignment with the first. Further image processing and analysis steps use a location-sensitive entropy based texture analysis of PCO. Validity of measuring PCO progression of the whole new system is assessed along with visual significance of scores. Reliability of the system is assessed. RESULTS: Analysis of PCO by the system shows ability to detect early progression of PCO, as well as detection of more visually significant PCO. Images with no clinical PCO produce very low scores in the analysis. Reliability of the system of analysis is demonstrated. CONCLUSION: This system of PCO analysis is evidence-based, objective and clinically useful. It incorporates flash detection and removal as well as location sensitive texture analysis. It provides features and benefits not previously available to most researchers or clinicians. Substantial evidence is provided for this system's validity and reliability