Stefano Midollini

Some rhodium(I) and rhodium(III) complexes with the tripod-like ligands RC(CH2PPh2)3 (R = Me: triphos; R = Et: triphos-I) and the X-ray crystal structure of [RhH3(triphos-I)]

Abstract The syntheses of [RhH3(triphos)] (8, triphos = CH3C(CH2PPh2)3) and the related compound [RhH3(triphos-I)] (triphos-I = EtC(CH2PPh2)3) are described, and the X-ray crystal structure of the latter is reported. The crystals are monoclinic space group P21/a, a 15.985(6), b 19.683(7), c 11.900(4) A, β 103.73(6)°, Z=4. The structure was solved by the heavy atom method and refined by full-matrix least-squares to the conventional R factor value of 0.057 for 2649 observed reflections. The metal atom is octahedrally coordinated by three phosphorus atoms and by three hydrogen atoms, each trans to one phosphorus. Complex 8 has been shown to react with CO to give [RhH(CO)(triphos)] (2). Compound 2 reacts with CH2=CHCO2Me to give only the branched insertion product [Rh(CH(CH3)CO2Me)(CO)(triphos)]. The complex [RhCl(CO)(triphos)] has been re-investigated and was obtained in a single isomeric form which has been assigned a five-coordinate structure. The five-coordinate compounds (RhX(CO)(triphos)] (X = Br and I) are also described.

Hydridodinitrogen and hydrido complexes of iron(II) with the linear tetratertiary phosphine hexaphenyl-1,4,7,10-tetraphosphadecane. Crystal structure of the complex [FeH(N2)((C6H5)2PC2H4P(C6H5)C2H4P(C6H5)C2H4P(C6H5)2]Br · C2H5OH

Abstract Treatment of the chromophore [FeX(P4)]+, where X = Br, I and P4 is the tetradentate open-chain ligand hexaphenyl-1,4,7,10-tetraphoshadecane, with sodium tetrahydroborate under helium or nitrogen gave cationic hydrido- or hydrido-dinitrogen-iron(II) complexes of formula [FeH(P4]X and [FeH(N2)(P4)]X. The structure of the [FeH(N2)(P4)]Br · C2H5OH complex was determined from three dimensional X-ray data collected by counter methods. The crystals are triclinic, space group P1- with cell dimensions a = 15.392(8), b = 16.109(10), c = 9.914(5) ]A, α = 69.57(8), β = 78.43(9), γ = 68.46(9)°. The structure was solved the heavy atom technique to a final conventional R factor of 0.053 over 1631 independent observed reflections. The structure consists of [FeH(N2)(P4)]+ cations, bromide anions, and solvating C2H5OH molecules. The metal atom is octahedrally coordinated with the four phosphorus atoms of the ligand in the equatorial plane and weith the hydrogen atom and one atom of the dinitrogen molecule in the axial positions.

Synthesis, properties and structures of the two “electron rich” cobalt-sulphur clusters [Co6(μ3-S)8(PEt3)6]1+,0

Abstract The reaction of hydrogen sulphide with [Co(H 2 O) 6 ](BF 4 ) 2 and triethylphosphine in the presence of sodium tetraphenylborate or tetrabutylammonium hexafluorophosphate gave the paramagnetic clusters [Co 6 (μ 3 -S) 8 (PEt 3 ) 6 ]( Y ) ( Y = BPh 4 , ( 1 ), PF 6 , ( 2 )). These compounds can be easily reduced by sodium napthalenide to the diamagnetic species [Co 6 (μ 3 -S) 8 (PEt 3 ) 6 ] · 2C 4 H 8 O ( 3 ). The molecular structures of 1 and 3 have been established by single-crystal X-ray diffraction methods. Crystal data: ( 1 ) space group P 1 , a = 19.481(9), b = 15.562(7), c = 12.390(b) A, α = 92.70(8), β = 94.50(7), γ = 94.10(9)°, Z = 2, ( 3 ) space group R 3 , a = 11.780(6) A, α = 92.50(7)°, Z = 1. Both structures were solved by the heavy atom method and refined by full-matrix least-squares techniques to the conventional R factors values of 0.050 for 1 and 0.044 for 3 on the basis of 4251 and 1918 observed reflections, respectively. The two clusters [Co 6 (μ 3 -S) 8 )(PEt 3 ) 6 ] 1+,0 are isostructural, the inner core consisting of an octahedron of cobalt atoms with all the faces symmetrically capped by triply bridging sulphur atoms. Each metal centre is additionally linked to a triethylphosphine group so that each cobalt atom is co-ordinated by four sulphur atoms and one phosphorus in a distorted square pyramidal environment. The addition of one electron whilst leaving unchanged the geometry of the inner framework, induces small changes in the structural parameters, the average CoCo and CoP distances being 2.794 (3) and 2.162 (2) A for 1 and 2.817 (3) and 2.138 (2) A for 3 respectively. Electrochemistry in non-aqueous solvents shows the electron-transfer sequence The tricationic species is stable only in the short time of cyclic voltammetric tests.

Aqueous solution chemistry of beryllium

Publisher Summary This chapter discusses aqueous solution chemistry of beryllium. Complexes of the beryllium ion are always 4-coordinate with, at most, minor deviations from regular tetrahedral geometry. The tetra-aqua ion is a very stable entity and substitution of one or more water molecules by monodentate ligands is not thermodynamically favorable except with fluoride, hydroxide, and phosphonate ligands. The aqueous solution chemistry of this ion is dominated by the ease of hydrolysis with the formation, principally, of the hydroxo-bridged species [Be3(OH)3(H2O)6] 3+ . Complex formation, then, is a process in which the ligand is usually competing with the hydrolysis reaction as the aqua-ion is present only in strongly acid conditions (pH less than ca. 3) where many ligands are protonated. The only monodentate ligands that can compete with hydrolysis are fluoride and phosphonates. Chelating ligands can form stable complexes with beryllium by virtue of the chelate effect. Greater use of beryllium will require the consideration of its role in the environment, and knowledge of speciation in naturally occurring waters will be needed.

Preparative, potentiometric and NMR studies of the interaction of beryllium(II) with oxalate and malonate. X-ray structure of K3[Be3(OH)3(O2C–CH2–CO2)3]·6H2O

Abstract The complexes formed by beryllium(II) with the bidentate ligands oxalate, L=(O2C–CO2)2−, and malonate, L=(O2C–CH2–CO2)2−, have been investigated in aqueous solution using both potentiometric and 9Be NMR measurements. The species [BeL(H2O)2], [BeL2]2−, [Be3(OH)3L3]3− and [Be3(OH)3(H2O)3L]+ have been identified and their formation constants have been determined at 25°C in 0.5 mol dm−3 NaClO4. The malonate complexes are much more stable than the oxalate ones. New crystalline salts of formula K3[Be3(OH)3L3]·nH2O have been isolated using conditions established with the aid of speciation calculations. The structure of K3[Be3(OH)3(malonate)3]·6H2O has been determined by an X-ray structure analysis: orthorhombic, space group Pc21n, a=9.011(3), b=14.041(4), c=18.761(9) A, Z=4. Each beryllium atom is tetrahedrally coordinated by two hydroxo groups and two oxygen atoms from the chelating malonate. The (Be(OH))3 core is a puckered six-membered ring with each hydroxo group bridging two beryllium centres.

Organomercury derivatives of the 2,4,6-trimercaptotriazine (H3TMT). X-ray crystal structure of (HgMe)3(TMT)

Abstract By reaction of RHgCl with Na3(C3N3S3)·9H2O, organomercury derivatives of formulae (HgR)3(C3N3S3) (R=Me, Et), have been synthesized and characterized. The methyl-derivative has been completely studied by X-ray diffraction analysis. The crystal and molecular structure consists of discrete (HgMe)3(C3N3S3) units, where the triazine ligand is linked through the sulfur atoms to three HgMe moieties in a “manxane” arrangement.

A new lead(II) inorganic–organic hybrid of the P,P′-diphenylmethylene-diphosphinate ligand: synthesis and X-ray characterization of the [Pb(CH2(P(Ph)O2)2)] complex

Abstract By reaction of lead(II) nitrate with P,P′-diphenylmethylenediphosphinic acid in water solution a new inorganic–organic hybrid of formula [Pb(CH2(P(Ph)O2)2)] has been synthesized and structurally characterized. The complex displays a polymeric columnar structure, the column being formed by two intersecting sinusoidal ribbons of lead(II) ions bridged by bifunctional phosphinate ligands. The intersections of the ribbons are constituted by dimeric units of pentacoordinated lead(II) ions.

Isostructural organic–inorganic hybrids of P,P ′ -diphenyl-methylenediphosphinate (CH 2 (P(Ph)O 2 ) 2 ) 2− with divalent transition metals

Abstract New organic–inorganic hybrid materials have been synthesized by reaction in water solution of manganese, cobalt or nickel acetates with P,P′-diphenylmethylenediphosphinic acid and all the two-dimensional structure coordination polymers obtained have been found to be isomorphous.

Facile reduction of carbon dioxide, carbonyl sulfide, and carbon disulfide by copper(I) borohydride. X-ray crystal structure of the complex [(triphos)Cu(O2CH)]

Abstract The copper(I)-borohydride complex [(triphos)Cu(BH4)] reacts with CO2, CS2, and COS under very mild conditions to give formate, dithioformate, or thioformate copper(I) complexes, respectively. A complete X-ray crystal structure determination has been carried out on the formate complex [(triphos)Cu(O2CH)].

Synthesis and X-ray structure of the thioethereal mercury(II) complex [N(CH2CH2SCHMe2)3HgCl]2(Hg2Cl6)

Abstract The thioethereal mercury complexes [N(CH2CH2SCHMe2)3HgX]2(Hg2X6) (X = Cl, Br) have been prepared by reaction of HgX2 with the tripodal ligand N(CH2CH2SCHMe2)3. The chloro derivative has been fully characterized by a crystal structure determination: space group Pl¯, a = 10.114(2), b = 11.230(5), c = 12.196(7)A, α = 86.11(4), β = 73.47(4), γ = 74.45(4)°, Z = 2. The complex shows a geometry intermediate between the trigonal bipyramidal and the tetrahedron. These distortions have been compared with those found in a series of mercury complexes [LHgX]+ containing the ligand tris(2-diphenylphosphinoethyl)amine, np3, or tris(2-dimethylaminoethyl)amine, Me6tren, the differential weakening of the apical N Hg bond being related to the electronegativity and to the σ-bonding capability of the ligand trans to the apical nitrogen.