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Conventional X-ray mammography has low diagnostic sensitivity for women with dense breasts. As a result, alternative contrast-enhanced screening tools such as dual energy mammography (DEM), computed tomography (CT), magnetic resonance imaging (MRI), and near-infrared fluorescence (NIRF) imaging are being used or investigated for these women. However, currently available contrast agents are non-ideal, have safety issues, and each imaging technique requires a different contrast agent. We therefore sought to develop a multimodal contrast agent that is functional for each breast imaging modality to simplify the diagnosis process and address the issues of existing contrast agents. Herein, we present a novel “all-in-one” nanoparticle (AION) multimodal imaging probe that has potent DEM, CT, MRI, and NIRF contrast properties and improved biocompatibility. AION were formed by co-encapsulation of a near-infrared fluorophore (DiR), silver sulfide nanoparticles (Ag(2)S-NP), and iron oxide nanoparticles (IO-NP) in PEGylated micelles. AION showed negligible cytotoxicity, which was in agreement with its minimal silver ion release profiles. AION generated strong contrast with all imaging modalities as demonstrated in phantom imaging. AION allowed in vivo tumor imaging as evidenced by the increase in contrast after injection. This study indicates the potential of AION as an effective multimodal contrast agent for breast cancer diagnosis with a range of imaging methods.

Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.

Kinetic studies of the ring-opening and reclosure reactions of thiamine and three other thiazolium ions (Q+) in aqueous solution, in the pH range 0–13, have been carried out by stopped-flow and conventional UV–VIS spectrophotometry. At high pH, ring-opening of thiamine exhibits a temporary diversion to the well-known ‘yellow form’. Otherwise, the ring-opening reactions are simply first-order in [OH–], consistent with rate-limiting attack of hydroxide ion at C(2) of the Q+ ring, producing a pseudobase, T°, which rapidly consumes a second equivalent of hydroxide ion to form the ring-opened enethiolate, ETh–. In contrast, ring closure of the enethiol in acidic solution exhibits rather complex kinetic behaviour; two processes are observed for most enethiols, including that derived from thiamine. Both the fast process (a) and the slower process (b) produce the thiazolium ion Q+ and they exhibit pH- and buffer-independent rate plateaux at low pH. Rapid, repetitive UV spectral scans and NMR spectral studies show that the two processes arise from the independent formation of Q+ from the two amide rotamers of the enethiol which do not equilibrate under the reaction conditions. The major amide rotamer (∼75%) gives rise to the fast process (a) and the minor rotamer to the slow reaction (b). The pH–rate profile and buffer catalysis studies reveal that the reclosure reaction undergoes a change in rate-limiting step from uncatalysed formation of T° at low pH to its general acid catalysed breakdown at higher pH. The latter process is characterized by a Bronsted α value of 0.70. Additionally, for process (b), a general base catalysed pathway for formation of T° can be observed, for which the Bronsted β value is 0.74. The mechanistic details of the ring-opening and reclosure pathways are discussed.

The four- and five-co-ordinate iridium(I) cations [Ir(dppe)2]+ and [Ir(CO)(dppe)2]+ react with B10H14, B10H13(Cl-6), and [B10H13]– to give a number of ionic compounds. The reaction between [Ir(dppe)2]Cl and B10H13X (X = H or 6-Cl) yields [IrIIICl(dppe)2H][B10H12X]. The complex [Ir(CO)(dppe)2]Cl reacts with [B10H13]–, in methanol solution, to give [IrI(CO)(dppe)2][B10H13] and, as a product of methanolic degradation, [IrIII(dppe)2H2][B9H14]. The latter crystallizes as pale yellow needles in the orthorhombic space group Ccca with a= 15.456(4), b= 23.936(4), c= 28.529(7)A, and Z= 8. The [B9H14]– anion is grossly disordered, but it is possible to determine the structure of the cation.

The title compound has been isolated as an unexpected product of the reaction between [NMe4][B3H8] and PPh2Cl, and has been examined by 1H, 31P, and 11B n.m.r. spectroscopy and by single-crystal X-ray analysis. The compound crystallizes in colourless prisms in the triclinic space group P with a= 12.15(5), b= 12.151(7), c= 9.523(4)A, α= 92.60(4), β= 103.48(3), γ= 116.33(4)°, U= 1 207.4(9)A3, and Z= 2. The structure has been solved using diffractometer data on 2 028 independent reflections; all the atoms have been included in the refinement which gives a final R of 0.043 and R′of 0.053. Interatomic distances along the chain are Cl(1)–B(1) 1.877(7), B(l)–P(2) 1.953(6), P(2)–B(3) 1.959(6), B(3)–P(4) 1.907(6), and P(4)–Cl(4) 2.025(2)A. The angles Cl(1)–B(1)–P(2) 110.1(3), B(1)–P(2)–B(3) 113.6(3), P(2)–B(3)–P(4) 117.1(2), and B(3)–P(4)–Cl(4) 113.5(2)° are all somewhat larger than tetrahedral, presumably due to non-bonded steric interaction.

Treatment of But2P(CH2)5PBut2, with iridium trichloride gives a mixture of the 16-atom ring dihydride [lr2H2Cl4{But2P(CH2)5PBut2}2], a co-ordinatively saturated cyclometallated hydride, [[graphic omitted]But2)])(1b), which is non-fluxional, and an unidentified complex. A better route to the cyclometallated hydride (1b) is to treat [Ir2Cl2(C8H14)4](C8H14= cyclo-octene) with the diphosphine. Complex (1b) takes up carbon monoxide to give the six-co-ordinate [[graphic omitted]But2)] and loses dihydrogen on heating [ca. 200 °C (15 mmHg)] to give the very dark carbene/ylide complex [[graphic omitted]But2)](3)/(4). This carbene/ylide complex takes up dihydrogen at 20 °C (1 atm) to give back (1b). The diphosphine But2PCH2CH2CHMeCH2CH2PBut2 reacts with IrCl3 to give the 16-atom ring chelate [Ir2H2Cl4(But2PCH2CH2CHMeCH2CH2 PBut2)2], no cyclometallated product being detected. However, the complex [[graphic omitted]But2)], can be prepared from [Ir2Cl2(C8H14)4] and the diphosphine. Hydrogen-1, 13C, and 31P n.m.r. and i.r. data are reported. The crystal structures of (1b) and of the carbene/ylide (3)/(4) have been determined. Cell dimensions are, for (1b), a= 1 231.8(3), b= 1 435.9(3), c= 1 485.4(3) pm, and β= 104.82(2)° and for (3)/(4), a= 1 232.6(3), b= 1 436.2(3), c= 1 480.7(3) pm, and β= 104.87(2)°. The structures are isomorphous, with space group P21/c and Z= 4.

Treatment of [PdCl2(NCPh)2] with Me2N[CH2]nNMe2(n= 5, 7, or 10) gives binuclear complexes trans-[Pd2Cl4{Me2N(CH2)nNMe2}2] in good yield. The crystal structures of the 16-atom ring (n= 5) and 20-atom ring (n= 7) complexes were determined from 2577 and 1154 diffractometer data, respectively, and were refined to R of 0.034 and 0.057, respectively. They are compared with the structures of trans-[Pd2Cl4{But2P(CH2)nPBut2}2](n= 5 or 7). The rings in the amine complexes adopt an elongated-chair (‘sofa’) conformation whilst those of the phosphine complexes have an elongated-boat (‘barge’) conformation. Factors affecting the conformations and stabilities of these large chelate rings are discussed. Crystal data are: [Pd2Cl4{Me2N(CH2)5NMe2}2]·C6H6, space group P, Z= 1, a= 8.425(2), b= 12.624(2), c= 8.217(2)Aα= 105.16(2), β= 98.12(2), γ= 71.83(2)°; [Pd2Cl4{Me2N(CH2)7NMe2}2]·C6H6, space group Cmca, Z= 4, a= 29.387(4), b= 8.030(2), c= 15.177(3)A.

The cyclometallated complex [[graphic omitted]But2}](1a) reacts with CO, CNMe, or CNBut(Y) in the presence of NaBPh4 to give the salts [[graphic omitted]But2}][BPh4](2). The carbonyl complex when treated with NaOMe gives the hydride [[graphic omitted]But2}]. We have previously reported that [PtCl2(NCBut)2] reacts with But2P(CH2)5PBut2 to give a number of species, including (1 a) inseparably mixed with another complex. We have now separated this complex and identified it as [[graphic omitted]But2}](3). The compound Ph3C+BF4– converts (1a) into the olefin complex [[graphic omitted]But2}][BF4](5). Attempts to deprotonate (5) and other complexes with various bases, to give (3), were unsuccessful; various products were formed for which some structures are suggested. Crystals of (3) are monoclinic, space group P21/c, with a= 1.2319(3), b= 1.4370(4), c= 1.4693(3) nm, and β= 104.58(2)°. The structure was determined from 2 457 Fo and refined to R= 0.049. The molecule is disordered.

The detailed molecular structure of [(CO)(PPh3)2HIrB3H7] has been determined by X-ray diffraction analysis. The colourless crystals are monoclinic, space group P21/n with a= 1 182.0(3), b= 2 189.4(4), c= 1 355.7(3) pm, β= 104.27(2)°, and Z= 4. The molecular structure (R= 0.032 for 4 119 reflections) features a four-vertex butterfly cluster (IrB3) with Ir on a ‘hinge’ position. The structure is interpreted in terms of a ‘capped octahedral’ seven-orbital 18-electron d4 iridium(V) complex in which the metal–borane bonding occurs predominantly via three two-electron two-centre iridium–boron bonds. The cluster bonding implications are discussed with reference to the ‘π-allyl’ and ‘borallyl’ bonding modes.

An improved synthesis of the known compound [(PMe2Ph)2(PtB10H12)] has been developed by deprotonation of B10H14 with NNN′N′-tetramethylnaphthalene-1,8-diamine followed by treatment with cis-[PtCl2(PMe2Ph)2]. This reaction has been applied to the 2,2′, 2,6′, and 1,5′ isomers of (B10H13)2 to prepare various isomeric platinahenicosaborane clusters [(PMe2Ph)2(PtB10H11–B10H13)] which differ either in the position of the conjuncto-linkage or the site of the platinum atom in the cluster. Appropriate modification of the reaction stoicheiometry in the case of 2,2′-(B10H13)2 led to the isolation of cisoid and transoid diplatinadocosaboranes [{(PMe2Ph)2(PtB10H11)}2]. The X-ray crystal structure of [(PMe2Ph)2(PtB10H12)] showed it to contain a platinaundecaborane cluster in which the tetrahapto B10H12 group is twisted by ca. 20° with respect to the PtP2 plane. Similarly, the molecular structure of the isomer of [(PMe2Ph)2Pt(η4-B10H11–B10H13)] obtained from 2,2′-(B10H13)2 is distorted by a twist of ca. 8°. A detailed n.m.r. study of a number of these clusters has been made, using the resonances of 1H, 11B, 31P, and 195Pt. In addition to permitting structural assignments, the data reveal a novel mutual pseudo-rotation of the η4-B10H11X group (X = H or B10H13) and the (PMe2Ph)2 grouping about the central Pt atom. For [(PMe2Ph)2(PtB10H12)] the two sets of 1H-{31P} methyl resonances at 100 MHz coalesce at 71.5 °C with an implied activation energy ΔG‡ of 79 ± 5 kJ mol–1 for the fluxional process. Similar activation energies were deduced for the various isomers of [(PMe2Ph)2(PtB20H24)].

A 31P n.m.r. study of the system [Pt2Cl4(PMe2Ph)2]–allene shows that at low temperatures (e.g. 213 K)trans-[PtCl2(PMe2Ph)(C3H4)] forms rapidly and reversibly. At 20 °C [Pt2Cl4(PR3)2](PR3= PPrn3, PMe2Et, or PMe2Ph) react with allene to give colourless complexes cis-[PtCl2(PR3)(C3H4)], the crystal structures of the PPrn3 and PMe2Ph complexes were determined by X-ray diffraction. Crystal data are for [PtCl2(PPrn3)(C3H4)]a= 15.461 (2), b= 11.437(2), c= 9.606(2)A, space group Pna21, with Z= 4 and for [PtCl2(PMe2Ph)(C3H4)]a= 8.398(2), b= 10.209(3), c= 15.677(4)A, space group P212121, and Z= 4. Final R factors are R= 0.026 and 0.029 respectively. These cis complexes dissociate very slowly in solution, in contrast with cis-[PtCl2(PPh3)-(C3H4)], which was previously reported to be unstable. Treatment of cis-[PtCl2(PMe2Ph)(C3H4)] with [Pt2Cl4-(PMe2Ph)2] gives what is probably the µ-allene complex cis,cis-[(PhMe2P)Cl2Pt(C3 H4) PtCl2(PMe2Ph)] which was too insoluble to characterize fully. Treatment of [NBun4]2[Pt2X6](X = Cl, Br, or I) with an excess of allene gives the salts [NBun4][PtX3(C3H4)]. Treatment of [NBun4][PtX3(C3H4)] with [NBun4]2[Pt2X6](X = Cl or Br) gave the µ-allene complexes [NBun4]2[X3Pt(C3H4)PtX3]. The NPrn4 salt was also made. Proton, 13C, and 31P n.m.r. data and i.r. data are given and discussed.

Addition of NR3(R = Me or Et) to the allene complex cis-[PtCl2(PPrn3)(C3H4)] rapidly gives the zwitterionic alkenyl complexes [PtCl2(PPrn3){C(CH2)CH2NR3}]. Addition of NH2But to the allene complex at or below –20° C gives an analogous complex, viz.[PtCl2(PPrn3){C(CH2)CH2NH2But}], but this with base, i.e. an excess of NH2But or preferably Na[OPri], immediately cyclizes to give [[graphic omitted]HBut}](5) the crystal structure of which has been determined and shown to contain a four-membered ring. Treatment of the allene complex with an excess of methylamine gives [[graphic omitted]HMe}2](6a) the crystal structure of which has also been determined and shown to contain an eight-membered ring. Benzylamine gives an analogous complex. Proton, 31P, and 195Pt n.m.r. data are given and discussed, as are i.r. data. Crystals of (5) are monoclinic, space group C2/c, with a= 19.653(3), b= 11.538(2), c= 18.785(2)A, β= 107.10(1)°, and Z= 8; R= 0.036 for 2 300 independent reflections. The complex (6a) is monoclinic, space group P21/n, with a= 11.315(3), b= 13.782(2), c= 11.385(3)A, β= 100.76(2)°, and Z= 2; R= 0.032 for 2 083 independent reflections.

E-Methyl t-butyl ketoxime, with sodium acetate and Na2[PdCl4] in methanol, cyclopalladates regiospecifically on a t-butyl methyl to give the chloride-bridged complex [Pd2{CH2C(CH3)2C(NOH)CH3}2Cl2](1a), the crystal structure of which has been determined (see below). The corresponding bromide and iodide complexes have been made, as have several mononuclear species by bridge-splitting reactions, e.g. of type [[graphic omitted]OH)CH3}X(L)](X = Cl or Br; L = CO, PMe2Ph, PPh3, or pyridine). The salts [Pd(CH2C(CH3)2C(NOH)CH3}(Ph2PCH2CH2PPh2)](X = l or BPh4) have also been prepared. E-Ethyl t-butyl and E-phenyl t-butyl ketoximes are similarly cyclopalladated, but oximes of other carbonyl compounds, e.g. trimethylacetaldehyde, methyl isopropyl ketone, di-isopropyl ketone, ethyl methyl ketone, or 2-methylcyclohexanone, give dark intractable products. In contrast, methyl t-butyl NN-dimethylhydrazone with Na2[PdCl4] and Na[O2CMe] cyclometallates regiospecifically on the single methyl group to give [Pd2{CH2C(NNMe2)But}2Cl2]. The corresponding bromide or iodide complexes have been made as have bridge-split derivatives (with PMe2Ph, PPh3, or pyridine) and also an acetylacetonate, [[graphic omitted]Me2)But}(acac)](6), the crystal structure of which has been determined. NN-Dimethylhydrazones of acetaldehyde, acetone, cyclohexanone, or 4-t-butylcyclohexanone cause decomposition on attempted cyclopalladation. Acetophenone NN-dimethylhdrazone cyclopalladates specifically on the 2 position of the benzene ring (i.e. not on the C-methyl group). Methyl t-butylketazine cyclopalladates specifically on a t-butyl methyl giving [Pd2{CH2C(CH3)2C(NNCMeBut)CH3}2Cl2]: dimetallation could not be effected. Acetoxime O-allyl ether in methanol is cyclopalladated with concomitant attack by OMe to give [[graphic omitted]C-(CH3)2}2Cl2]. The corresponding ethoxy-compound is formed in ethanol; cyclohexanone oxime O-allyl ether is similarly palladated. Crystal data are: (1a), Monoclinic, space group P21/c, a= 7.312(1), b= 8.539(2), c=28.478(4)A, β= 91.74(1)°, and Z= 4; (6), Triclinic, space group P, a= 9.573(3), b= 10.714(3), c= 8.983(2)A, α= 94.41(2), β= 113.76(2), γ= 104.65(2)°, and Z= 2.

The arachno-anion [B9H14]– reacts with trans-[Ir(CO)CI(PPh3)2], trans-[Ir(CO)CI(PMe3)2], [{Ir(cod)CI}2], and [{Rh(cod)CI}2](cod = cyclo-octa-1,5-diene) to give low yields of the nido-6-metalladecaboranes [6-H-6,6-(PPh3)2-nido-6-lrB9H13], [6-H-6,6-(PMe3)2-nido-6-IrB9H13], [6-(η2:η2-cod)-6-Cl-nido-6-IrB9H13], and [6-(η2:η2-cod)-6-Cl-nido-6-RhB9H13] respectively. These products have been characterized by single- and multiple-resonance n.m.r. spectroscopy and by single-crystal X-ray diffraction analysis on [6-H-6,6-(PPh3)2-nido-6-IrB9H13]. This last compound crystallizes in the orthorhombic space group Pna21, with a = 1 942.7(4), b= 1 196.7(2), c= 1 552.2(3) pm, Z= 4, and the structure (R= 0.024 for 2 333 observed reflections) of the metallaborane unit is that of a ten-vertex nido-cluster similar to that of B10H14, with the metal atom in the 6-position in the open face. The geometry about the iridium(III) atom is essentially octahedral, the metal being incorporated in the cluster via a direct Ir–B(2) bond and two Ir–H–B bridge bonds which differ in that one is trans to Ir–H(terminal) and the other trans to Ir–P.

The spiro-dimer of α,α′-bis(methoxycarbonyl)-o-quinodimethane is allocated the stereochemistry (1) by comparison of its properties with those of the isomers (6a) and (6b) obtained from it by photolysis. Under acidic conditions the isomers (1) and (6a) give mainly epimeric products [the epimeric tosylates (9) with toluene-p-sulphonic acid, and the epimeric dibenzocycloheptenes (8a) and (8b) and lactones (11) with boron trifluoride–diethyl ether] showing that the isomers (1) and (6a) differ in configuration at the benzylic carbon adjacent to the spiro-centre. A single-crystal X-ray structure determination shows that the major thermal rearrangement product of compound (1) has structure (4) rather than the structure (2) previously proposed; the minor rearrangement product is compound (7). The thermal rearrangements of compounds (1) to (4), (6a) to (7), and (6b) to (2) are formal 1,3-shifts following the forbidden suprafacial-retention geometry; rearrangement by a radical dissociation-recombination mechanism is likely.

The compound PBut2[C6H3(OMe)2-2,6] reacts with iridium trichloride in propan-2-ol to give the purple five-co-ordinate hydride [[graphic omitted]But2-2)}2](1). This hydride in solution is converted by air into the red paramagnetic iridium(II) complex [[graphic omitted]But2-2)}2](3) which can be converted back to (1) when treated with Na[BH4]. The hydride (1) takes up small ligands (L) such as pyridine or carbon monoxide reversibly to give colourless adducts [[graphic omitted]But2-2)}2]. Complex (3) takes up dioxygen reversibly to give a purple complex, probably [[graphic omitted]But2-2)}2], reacts with NO to give brown diamagnetic [[graphic omitted]But2-2)}2] and with CO to give a pale green complex which in air becomes intensely blue, then red, and finally gives the colourless C-cyclometallated iridium(III) complex [[graphic omitted]}{OC6H3(OMe-3)(PBut2-2)}](7; L = CO). The dioxygen adduct is slowly converted into the purple, co-ordinatively unsaturated, C-cyclometallated complex [[graphic omitted]But2-2)}](8). Complex (8) takes up small ligands such as CO, pyridine, or MeNC more strongly than (1) to give six-co-ordinate species. The structure of the title complex (7; L = MeNC) has been determined by X-ray diffraction. The crystals are monoclinic, space group P21/c, with a= 13.471 (2), b= 16.043(3), c= 16.690(3)A, and β= 104.22(1)°. The complex has a five-membered IrPC2O chelate ring bound to a highly strained four-membered IrPC2 ring. Complex (8) also takes up PMe2Ph; this addition is reversed on heating and the 31P n.m.r. spectrum at 300 K shows that rapid PMe2Ph exchange occurs (at 233 K exchange does not occur). Treatment of iridium carbonyl chloride solution with PBut2[C6H3(OMe)2-2,6] and PBut2[C6H3(OMe)2-2,3] gives yellow complexes of the type [[graphic omitted]But2-2)}2], isomeric and much more stable than the one described above. Hydrogen-1, 13C, and 31P n.m.r. and i.r. data are given.

The new diphosphine But2PCH2CHMeCH2CH2CH2PBut2(L) is shown to have 13C n.m.r. shifts which can be calculated empirically from the 13C n.m.r. shifts of related diphosphines. It reacts with [PdCI2(NCPh)2] to give the cyclometallated complex [[graphic omitted]But2)](1c), with the 2-methyl group in a pseudo-equatorial position, as shown by the crystal structure. With [PtCl2(NCBut)2] it gives [Pt2Cl4L2] as a complex mixture of isomeric 16-atom ring chelates, which, on treatment with CF3COOH followed by LiCl, gives [[graphic omitted]But2)]; this was not isolated pure but probably has a structure similar to (1c). Compound L also reacts with [Ir2Cl2(C8H14)4](C8H14= cyclo-octene) to give the cyclometallated hydride complex [[graphic omitted]But2)](2c) with an equatorial methyl group. Some of the isomer with a pseudo-axial methyl group was also formed but it slowly, but completely, isomerises to (2c) in solution. Compound (2c) does not lose dihydrogen to give a carbene on heating, in contrast to [[graphic omitted]But2)]. Compound L reacts with [Rh2Cl2(C8H14)4] to give [[graphic omitted]But2)](2e), but with RhCl3·3H2O it also gives two other species, probably rhodium(I)–olefinic diphosphine complexes. Compound (2e) with sodium propan-2-oxide and CO gives [[graphic omitted]But2)]. Proton, 13C, and 31P n.m.r. and i.r. data are given. Cell dimensions: (1c)a= 1.1907(3), b= 1.6466(4), c= 1.3537(4) nm, and β= 103.99(2)°; (2c)a= 1.1954(4), b= 1.6509(5), c= 1.3665(5) nm, and β= 104.18(3)°.

N-methyl-N-nitrosobenzylamine (Q) is not cyclo-(ortho-)palladated by Na2[PdCl4] but gives a complex of type [PdCl2O2]. In contrast N-Methyl-N-nitrosobenzylamine is readily ortho palladated to give the chloro-bridged complex [[graphic omitted]6H4}CI2](4a). This was converted into a mononuclear acetylacetonate (5a) and into species [[graphic omitted]6H4}ClL], L = PPh3( crystal structure determined), PMe2Ph, or pyridine, (6a), (6b), or (6c) respectively. With two moles of PPh3 per palladium the Pd–NO bond is broken giving the σ-aryl species [Pd{C6H4N(NO)CH3}Cl(PPh3)2](7a), the crystal structure of which has also been determined. With 1,2-bis(diphenylphosphino)ethane (dppe), (4a) gives the ion [[graphic omitted]6H4}(dppe)]+ isolated as its tetraphenylborate salt (8a). Some palladated derivatives of N-ethyl-N-nitrosoaniline and (4-methoxy)-N-methyl-N-nitrosoaniline were made similarly. With K2[PtCl4]N-methyl-N-nitrosoaniline gives a red material which was not obtained pure but which gave a mononuclear acetylacetonate [[graphic omitted]6H4}(acac)](5c) and bis-phosphine complex [Pt{C6H4N(NO)CH3}Cl(PPh3)2](7d) analogous to the palladium complex. N-Ethyl-N-nitrosoaniline reacted similarly. Crystals of (6a) are triclinic, space group P, with a= 9.990(2), b= 15.195(3), c= 9.276(2)A, α= 104.05(2), β= 97.92(2), γ= 89.47(2)°, and Z= 2. Those of (7a) are monoclinic, space group P21/c, with a= 12.047(2), b= 21.794(4), c= 16.402(2)A, β= 108.54(1)°, and Z= 4. Both compounds crystallise with a molecule of CH2Cl2. Least-squares refinements gave final R values of 0.089 for (6a) and 0.083 for (7a).

A series of complexes of type cis-[PtCl2(PR3)Q](PR3= PMe3, PEt3, PPrn3, or PMe2Ph; Q = prop-2-en-1-ol, but-1-en-3-ol, or 3-methylbut-1-en-3-ol) have been prepared. The crystal structure of cis-[PtCl2(PMe2Ph)-(CH2CHCH2OH)] is described : no intramolecular hydrogen bond is present. Crystal data : space group P21/n, a= 12.540(3), b= 10.668(7), c= 10.929(2)A, β= 97.02(2)°, and Z= 4. The complexes cis-[PtCl2(PR3)Q] have been studied by variable-temperature 1H and 31P n.m.r. spectroscopy. There is no evidence for rotamers, as found with other olefin complexes. At room temperature slow dissociation to give the bridged complex [Pt2Cl4-(PR3)2] and the free allyl alcohol occurs. The complex cis-[PtCl2(PMe2Ph)(CH2CHCH2OH)] does not exchange rapidly with free allyl alcohol and separate resonances due to free and complexed allyl alcohol could be observed : in contrast [NBun4][PtCl3(CH2CHCH2OH)] exchanges rapidly with free allyl alcohol on the n.m.r. time scale. N.m.r. studies of the interaction between chloro-bridged complexes of the type [Pt2Cl4(PR3)2]{and also [Pt2Br4(PMe2Ph)2]} and allylic alcohols show that at low temperatures the bridged species is rapidly and reversibly converted into trans-[PtCl2(PR3)(CH2CHCR1R2OH)] together with some of the O-bonded species, trans[[graphic omitted]H)]. Above ca. 260 K the resonances start to broaden due to exchange with the bridged complex and have also become much less intense due to reversion back to the bridged complex: cis-[PtCl2(PR3)(CH2CHCR1R2OH)] is also gradually formed above ca. 260 K. A [Pt2Br4(PMe2Ph)2]–CH2CHCH2OH system also shows the presence of trans-[PtBr2(PMe2Ph)(CH2CHCH2OH)] and in this case the cis isomer forms to a detectable extent even at 213 K. The bridged complex [Pt2Cl4(PPrnBut2)2] containing the bulky phosphine shows the presence of rotamers at 243 K and with allyl alcohol two rotamers trans-[PtCl2(PPrnBut2)(CH2CHCH2OH)] form at 213 K. The 1H and 31P n.m.r. and i.r. data are given and discussed.

The η1-Ph2PCH2PPh2(dppm) complexes [Pt(CCR)2(η1-dppm)2](R = Ph, p-tolyl, or Me) are used to give high-yield syntheses of heterobimetallic complexes with AgI, AuI, HgII, or CdII, in which the d10-metal can be 2-, 3-, or 4-co-ordinate.

Treatment of chloro-bridged complexes [Pt2Cl4(PR3)2](PR3= PMe2Ph, PEt3, or PPrn3) with buta-1,3-diene over several days gives the µ-butadiene complexes cis,cis-[Pt2Cl4(PR3)2(µ-C4H6)]; such complexes have not previously been fully characterized. Buta-1,3-diene is prochiral and the product is shown to be the meso isomer for PR3= PMe2Ph, by X-ray crystallography. A low-temperature study in CDCl3 shows that at –30 °C buta-1,3- diene reacts rapidly and reversibly with [Pt2Cl4(PPrn3)2] to give trans-[PtCl2(PPrn3)(C4H6)]; a very small amount of cis-[PtCl2(PPrn3)(C4H6)], in which the butadiene is monodentate, was also probably formed. Treatment of [NBun4]2[Pt2X6] with buta-1,3-diene gave the µ-butadiene complexes [NBun4]2[Pt2X6(µ-C4H6)](X = Cl or Br). Treatment of [Pt2Cl4(PMe2Ph)2] with isoprene at –60 °C reversibly gives a new species, probably trans-[Pt2Cl2(PMe2Ph)(isoprene)], and at room temperature probably cis-[PtCl2(PMe2Ph)(isoprene)], although we could not separate this cis species from the bridged complex. Treatment of cis,cis-[Pt2Cl4(PMe2Ph)2(µ-C4H6)] with an excess of dimethylamine (even at –78 °C) rapidly gave [(PhMe2P)Cl[graphic omitted]tCl(PMe2Ph)](5a); a similar reaction gave the PEt3 complex (5d), the crystal structure of which shows the presence of two trans-fused five-membered rings. Treatment of cis,cis-[Pt2Cl4(PPrn3)2(µ-C4H6)] with methylamine similarly gave [(Prn3P)Cl[graphic omitted]tCl(PPrn3)] as a mixture of three isomers due to the positioning of the N–Me groups; one isomer was isolated pure. Proton, 13C, 31P, and 195Pt n.m.r. and i.r. data are given. Crystals of both the title compounds are monoclinic, space group P21/n, with Z= 2 and molecular symmetry Ci. Those of [Pt2Cl4(PMe2Ph)2(µ-C4H6)] have a= 1.9658(4), b= 0.9741(3), c= 0.6557(1) nm, and β= 94.24(2)°. Those of (5d) have a= 0.8015(3), b= 1.3461(3), c= 1.3070(3) nm, and β= 97.56(3)°. Final R factors were 0.042 for 1 391 and 0.040 for 1 584 observed reflections, respectively.

The structures of the large neutral boranes 2,2′-bi(nido-decaboranyl), 2,2′-(B10H13)2, m.p. 178 °C, and 2,6′- bi(nido-decaboranyl), 2,6′-(B10H13)2, m.p. 154 °C, have been established by single-crystal X-ray diffraction. The 2,2′ isomer is tetragonal, space group l41cd, with a= 11.901(3), c= 23.135(4)A, molecular symmetry C2; the 2,6′ isomer is orthorhombic, space group Pbca, with a= 14.673(3), b= 19.765(4), and c= 11.580(3)A. The intercluster B–B bond lengths are respectively 1.692(3) and 1.679(3)A, and there is a lengthening of 0.015 A of the adjacent cluster B–B distances when compared with the corresponding distances in decaborane(14) itself. The 1H-{11B} and 11B n.m.r. behaviour of the two isomeric conjuncto-boranes has been investigated and the results for the 2,2′ isomer are discussed in some detail. Infrared and u.v. spectroscopic data are presented. The unambiguous determination of the structures permits a discussion of possible synthetic mechanisms.

Crystals of the title compound are triclinic, space group P, with three dimeric molecules in the reduced cell of dimensions a= 12·313, b= 12·755, c= 9·352 A, α= 102·8, β= 91·6, γ= 61·3°. The structure was determined by Patterson and Fourier methods from 3126 visually estimated photographic data, and refined by least-squares to R 10·6%. One third of the molecules lie on centres of symmetry with the [graphic omitted] ring necessarily planar, and the remainder are in general positions, with the central ring ‘folded’ by 14° about the Al ⋯ Al line. Al ⋯ Al is 2·687, Al–C(bridge) 2·144, and Al–C(terminal) 1·977 A; the Al–C–Al bridge angle is 77·6°.

Iridanonaboranes and iridadecaboranes which have adjacent open-face bridging H atoms and terminal Ir–H atoms readily lose H2 in formal cluster oxidations which involve stable isolable iridium (V) species.

The title compound, [Cu(η2-B5H8)(PPh3)2], crystallises as colourless needles in the monoclinic space group P21/c with a= 14.393(2), b= 12.291(2), c= 20.194(3)A, β= 105.50(1)° and Z= 4. The structure was solved from diffractometer data on 1 998 independent reflections by use of Patterson and electron-density syntheses. Refinement by block-diagonal least-squares gave a final R of 0.0547. The molecular structure can be described as being derived from that of nido-B5H9 by replacing one of the basal bridging hydrogen atoms with a bridging Cu(PPh3)2 group such that B(2)–Cu 2.209(13) and B(3)–Cu 2.236(13)A. The dihedral angle between the planes B(1), B(2), B(3) and Cu,B(2), B(3) is 178.4° the angle P(1)–Cu–P(2) is 123.4(1)°, and the mid-point between B(2) and B(3) is 0.20 A from the CuP2 plane. The copper atom is thus approximately trigonal planar and is formally 16-electron species, being bonded to the pentaborane unit only via a three-centre bond between Cu. B(2), and B(3). All the borane hydrogen atoms were located and their positions preclude the possibility of bonding via CU–H–B bonds.

Treatment of [PdCl2(NCPh)2] with glutaraldehyde bis(dimethylhydrazone) gives the stable 16-atom ring binuclear complex [Pd2Cl4{Me2NNCH(CH2)3CHNNMe2}2] in high yield. The crystal structure has been determined. The crystals are Triclinic, with unit-cell dimensions a= 8.660(2), b= 11.909(3), c= 7.407(2)A, α= 106.20(2), β= 102.75(2), γ= 82.83(2)°, Z= 1, and space group P. Factors affecting the conformation and stability of the complex are discussed and the structure is compared with those of other complexes containing large chelate rings.

Crystals of the title compound and of the corresponding platinum compound are isostructural. An X-ray crystal structure analysis of the palladium compound shows it to contain a π-allyl–metal bond. The bidentate acetylacetonate group completes the planar co-ordination around palladium.

Crystals of [Fe3(CO)9(PMe2Ph)3] are orthorhombic, space group Pbca, with a= 16·76, b= 18·75, c= 23·43 A, Z= 8. The structure was refined by least-squares with isotropic temperature factors to a final R of 11·4% for 1394 independent reflections. The molecule retains the skeleton of Fe3(CO)12, the isosceles triangle of iron atoms having its shortest (2·540 A) side bridged by two carbonyl groups whilst the two longer (2·688 A) sides are unbridged. The three phosphine molecules, one attached to each iron atom, occupy co-ordination positions which place all three phosphorus atoms coplanar with the triangle of iron atoms.

Crystals of the title compound are triclinic, space group P, with one centrosymmetric dimer in the reduced cell of dimensions a= 9·565, b= 10·813, c= 8·328 A, α= 106·2, β= 111·8, γ= 102·3°. The structure was determined by Patterson methods from 1636 observed data, visually estimated from Weissenberg photographs, and refined by least-squares methods to R 9·1%. The Al ⋯ Al vector (2·702 A) is almost normal (84·4°) to the planes of the bridging phenyl groups; Al–C distances are 2·182 (bridge) and 1·958 A(terminal), and the Al–C–Al bridge angle is 76·5°.

The crystal and molecular structure of (B10H13)2O has been determined by single-crystal X-ray diffractometry. The crystals are monoclinic with a = 24.838(6), b= 6.816(3), c= 10.132(3)A, β= 98.43(2)°, U= 1 697(1)A3, Z = 4, Dc= 1.011 g cm–3, F(000)= 536. Space group C2/c. The molecular structure comprises two B10H13 groups joined at the 6,6′-positions to the O atom. The molecule has crystallographic symmetry C2 with B–O distances of 1.358(2)A and a large B–O–B angle of 139.1(2)°. The conformation may be specified by the B(2)–B(6)–O–B(6′) torsion angle of –71°. The intra-cluster B–B distances are similar to those in B10H14, though there is a slight increase in the five B–B distances in each cluster involving those boron atoms [B(2), B(5), and B(7)] directly linked to B(6). There is also an enhanced asymmetry of the B–H–B(6) bridge bonds, with the H–B(6) being 0.14 A longer than H–B(5) and H–B(7).

Treatment of [W(CO)4{Ph2PCH(COPh)PPh2}] with hydrazine hydrate promotes a 4- to 7-membered ring expansion to give the title compound, the X-ray crystal structure of which has been determined.

The compound [7-(PMe2Ph){7-PtB16H18-9′-(PMe2Ph)]} is a complex of a macropolyhedral 16-vertex borane ligand based on the structure of an as yet unknown B6–B10conjuncto-borane; it is the first example of a contiguous 17-vertex cluster species, and has a number of other interesting features.

One of the products from the reaction of 6,6′-(B10H13)2O with cis-[PtCl2(PMe2Ph)2]is [Pt2(η3-B6H9)2(PMe2Ph)2], which is shown by X-ray crystallography to have a Pt–Pt bond with two bridging bidentate η3-nido-hexaboranate ligands.

The novel metallaborane [(PMe2Ph)2(Pt2B8H14)] consists of the four-vertex and eight-vertex subclusters {Pt2B2} and {Pt2B6} conjoined at a common Pt–Pt edge; it can be regarded as an iso-arachno-diplatinadecaborane.

The iridium(III)closo-cluster structure of [µ-1,2-(MeCO·O)-2-H-2,10-(PPh3)2-closo-1,2-ClrB8H7], which also contains a novel acetate bridge, contrasts with the otherwise ostensibly isoelectronic iridium (V)iso-nido-cluster structure of [(PPh3)(Ph2P[graphic omitted]H6(OMe)C(OH)}]

One of the isomers of B20H26 obtained by the photolysis of B10H14 has been shown by single-crystal X-ray structure analysis to be 2,2′-bi(nido-decaboranyl).

The occurrence and stereochemistry of a rapid reversible C–H fission in [[graphic omitted]But2)] is established by n.m.r. spectroscopy, including triple resonance INDOR, and by X-ray crystallography.

The molecular structure of the novel compound [1,1,2-(CO)3-1-(PPh3)-2,2-(Ph2P-ortho-[graphic omitted]4H2)], isolated as an advanced degradation product from the reaction of closoB-10H102– with trans-[Ir(CO)Cl(PPh3)2] in methanolic solution, is based on a closed {Ir2B4} octahedral cluster with the metal atoms occupying adjacent vertices.

Treatment of [PdCl2(NCPh)2] with But2 PCH2CH2CHMeCH2CH2PBut2(Q) gives the binuclear complex [Pd2Cl4(But2PCH2CH2CHMeCH2CH2PBut2)2]. The crystal structure of this 16-atom ring complex shows that the two methyl substituents on the ring occupy ‘corner positions’ and the C5 chains are not in the extended conformation. The crystals are monoclinic, space group Pn, with unit-cell dimensions a= 8.616(2), b= 28.485(5), c= 12.127(2)A, β= 109.35(2)°, and Z= 2, final R= 0.07. A variable-temperature 31P n.m.r. study shows the ring to be fluxional. With [PtCl2(NCPh)2], Q gives a complex [(PtCl2Q)x](also fluxional) and a cyclometallated complex [graphic omitted]But2)] abbreviated to [PtCl(P–C–P)], [PtCl2Q] with CF3COOH gives [Pt(OOCCF3)(P–C–P)], and [PtCl(P–C–P)] with Na[BH4] gives [PtH(P–C–P)]. Infrared and 1H and 31P n.m.r. data are given.

The equilibrium constants for hydration of the 4-amino-, 4-methylamino-, and 4-dimethylamino-derivatives of ααα-trifluoroacetophenone have been determined in mixtures of dimethyl sulphoxide (DMSO) and D2O (or H2O) using 19F n.m.r. spectroscopy. The dimethylamino-compound follows the pattern observed earlier for the 4-methoxy-compound, i.e. in mixtures up to 80 mol % DMSO these compounds are more highly hydrated than in pure water. The extent of hydration of the amino- and methylamino-compounds, on the other hand, decreases steadily as the water content of the mixture is decreased. The difference in behaviour of the two groups of compounds is attributed to the presence of acidic protons in the unhydrated forms of the amino- and methylamino-compounds, which are able to form strong hydrogen bonds to DMSO. The results indicate the strong solvent dependence to be expected for σ+ substituent constants for the three kinds of amino-group. A sampling of other carbonyl compounds that undergo hydration revealed a considerable variation in the response of such compounds, equilibrium constants to changes in DMSO–water composition, with only one compound, 2-nitrobenzaldehyde, showing the sort of response that is shown by the 4-dimethylamino- and 4-methoxy-derivatives of trifluoroacetophenone.

Addition of bromine to trans-[PtCl2(PEt3)2] in chloroform solution gives a single product, all-trans-[PtBr2Cl2(PEt3)2], provided that light is excluded. In the presence of light, halogen scrambling occurs to give a mixture of species [PtBrxCl4–x(PEt3)2], x= 0–4, with trans phosphines. Previously, the importance of light to this scrambling reaction had not been realized. In the dark, platinum(II) complexes trans-[PtCl2(PEt3)2] or trans-[PtBr2(PEt3)2] are poor at promoting halogen scrambling in trans-[PtBr2Cl2(PEt3)2], the structure of which has been determined by X-ray diffraction. Crystals are monoclinic with a= 9.414(2), b= 13.146(3), c= 8.656(1)A, and β= 103.10(2)°. The molecule has a crystallographic centre of symmetry and the structure has been refined to a final R of 0.030 for 1 108 reflections.

The title complex was prepared and shown to be resistant towards cyclometallation, as were the corresponding dibromo- and di-iodo-complexes. Crystals of the title compound are orthorhombic, space group P212121, with a= 1 263.1(3), b= 2 610.5(10), c= 685.3(2) pm, and Z= 4. The molecule has approximate C2 symmetry, with both camphoryl groups to the same side of the co-ordination plane, while the two oxime O–H groups on the other side engage in an unusual hydrogen-bond chelate system with a chlorine atom of a neighbouring molecule.

The reaction of trans-[Ir(CO)Cl(PPh3)2] with closo-[B10H10]2– in MeOH solution has been found to yield a number of novel structural types; one of these has been identified by single-crystal X-ray diffraction analysis as the ten-vertex iso-nido-iridacarbadecaborane [{IrC–(OH)[graphic omitted]6H4PPh2)(PPh3)].

The highly efficient intramolecular catalysis by the carboxy-group of the hydrolysis of simple dialkylmaleamic acids is itself subject to external general acid catalysis. The kinetic characteristics of the general acid catalysed reaction are those expected for a diffusion-controlled proton transfer. At high concentrations of general acid, external catalysis disappears. This is shown to result from a change in rate-determining step, and is thus evidence for an intermediate on the reaction pathway. The intermediate can only reasonably be a tetrahedral addition intermediate. Kinetic evidence is now available for all the major steps on the reaction pathway, and the requirements for an enzyme catalyst carrying out the reaction can be specified in detail. The full mechanism specifically implicates the O-protonated amide as the reactive species in dilute acid.

The reaction of cis-[PtCl2(PMe2Ph)2] with an excess of [B9H14]– gives 4,4-bis(dimethylphenylphosphine)-arachno-4-platinanonaborane, [4,4-(PMe2Ph)2-4-PtB8H12], (I), in high yield. The pale yellow crystals are monoclinic, space group C2/c, with a= 1.977 1(8), b= 1.302 5(4), c= 1.977 3(4) nm, β= 110.99(3)°, Z= 8, and the molecular structure is that of a nine-vertex arachno-platinanonaborane in which the B8 unit shows trihapto-bonding to the metal centre. The compound is also formed in lower yield from several other polyhedral borane derivatives. The 14-vertex bis(dimethylphenylphosphine)bis-µ-(2–4-η-nido-hexaboranyl)-diplatinum(Pt–Pt), [Pt2(B6H9)2(PMe2Ph)2], is also formed in moderate yield from the [B9H14]– reaction, and this offers the most convenient route yet established for its preparation. Treatment of (I) with KH followed by cis-[PtCl2(PMe2Ph)2] gives the very stable diplatinum compound 6,6,9,9-tetrakis(dimethylphenylphosphine)-arachno-6,9-diplatina-decaborane, [6,6,9,9-(PMe2Ph)4-6,9-Pt2B8H10], (II). The colourless crystals are monoclinic, space group C2/c, with a= 1.376 2(3), b= 1.510 5(4), c= 1.921 0(3) nm, β= 92.59(2)°, and Z= 4; the molecular structure is that of an arachno-diplatina-decaborane which features a bis(trihapto) B8 unit. It is topologically similar to, but not identical with, the arachno-decaborane anion [B10H14]2–. The 1H, 11B, 31P, and 195Pt n.m.r. behaviour of both title compounds has been investigated in detail using both single and double resonance techniques, and a number of important structural correlations emerge.

The reactions of arachno-6,9-(SMe2)2B10H12 and of arachno-6,9-(MeCN)2B10H12 with the complex cis-[PtCl2(PMe2Ph)2] give moderate yields of the nido-platinaundecaborane [8-Cl-7,7-(PMe2Ph)2-7-PtB10H11] which has been characterised by single-crystal X-ray diffraction analysis. Analogous reactions with the dimeric species [{PtCl2(PR3)}2](R3= Me3–nPhn, n= 0, 1, or 2), by contrast, give the nido-platinaundecaboranes [7-Cl-7-(PR3)-8-(SMe2)-7-PtB10H11] which have been characterized by single- and multiple-resonance n.m.r. spectroscopy. Additional products of the reactions include the arachno nine-vertex species 4-(MeCN)B9H13 and 4-(SMe2)B9H13.

Treatment of complexes of type mer-[IrCl3(PMe2R)3](R = Ph or Me) with strong bases, LiNPri2, LiBun, or Li(CH2)5Li, gives the three-membered ring metallocycles [Ir[graphic omitted]MeR)(PMe2R)2], (4a) and (4b), in high yield. Treatment of mer-[IrCl3{PMe(CH2Ph)2}3] with LiNPri2 probably gives a mixture of geometrical and optical isomers [Ir[graphic omitted]HPh)}{PMe(CH2Ph)2}2], (6) and (7). These three-membered ring metallocycles with hydrogen chloride are quantitatively converted back to mer-[IrCl3(PR3)3]. The reaction of complex (4a) with X2(X = Cl, Br, and I) gives [IrCl2X(PMe2Ph)2(PMePhCH2X)](8a), (8b), and (8c) respectively. The mer isomer (8a) on irradiation with visible light gives the corresponding fac isomer (9). I.r., 1H, 13C, and 31P n.m.r. data are given and discussed. The crystal structure of (4a) has been determined and refined to R 0.047. Cell dimensions are a= 11.619(2), b= 9.248(2), c= 25.498(5)A, and Z= 4, space group P212121.