The crystal and molecular structures of dioxo mo(VI) complexes of tripodal,tetradentate N,S-donor ligands

The crystal and molecular structures of the complexes MoO₂((SCH₂CH₂)₂NCH₂CH₂SCH₃), I and MoO₂((SCH₂CH₂)₂NCH₂CH₂N(CH₃)₂), II, have been determined from X-ray intensity data collected by counter methods. Compound I crystallizes in two forms, Ia and Ib. In form Ia the space group is P2₁/n with cell parameters a = 7.235(2), b = 7.717(2), c = 24.527(6) Å, β = 119.86(2)°, V = 1188(1) ų, Z = 4. In form Ib the space group is P2₁/c with cell parameters a = 14.945(5), b = 11.925(5), c = 14.878(4) Å, β = 114.51(2)°, V = 2413(3) ų, Z = 8. The molecules of I in Ia and Ib are very similar having an octahedral structure with cis oxo groups, trans thiolates (cis to both oxo groups) and N and thioether sulfur atoms trans to oxo groups. Average ditances are MoO = 1.70, MoS (thiolate) = 2.40, MoN = 2.40 and MoS (thioether) = 2.79 Å. Molecule II crystallizes in space group P2₁2₁2₁ with a = 7.188(1), b = 22.708(8), c = 7.746(2) Å, V = 1246(1) ų and Z = 4. The coordination about Mo is octahedral with cis oxo groups, trans thiolates and N atoms trans to oxo. Distances in the first coordination sphere are MoO = 1.705(2), 1.699(2), MoS = 2.420(1), 2.409(1) and MoN = 2.372(2), 2.510(2) Å. The conformational features of the complexes are discussed. Complex I displays MoO and MoS distances which are very similar to those found by EXAFS in sulfite oxidase. This similarity is discussed.     

The synthesis of technetium(V) complexes containing sterically bulky thiolate ligands. The molecular structure of tetrabutylammonium oxotetrakis(2,4,6-trimethylbenzenethiolato)technetate(V)

The reactions between [TcOCl₄]⁻ and the sterically bulky thiols ArSH (Ar = 2,4,6-Me₃C₆H₂, 2,4,6- Prⁱ₃C₆H₂ and 2,6-Ph₂C₆H₃) in methanol afford complexes of formula [TcO(SAr)₄]⁻ which may be isolated as salts with bulky organic cations. The molecular structure of [Buⁿ₄N][TcO(2,4,6-Me₃C₆H₂S)₄] was determined by X-ray diffraction methods. The Tc(V) centre was found to adopt the expected square pyramidal geometry in which an oxo group occupies the apical site and the four thiolate sulphurs the basal sites. The TcO distance is 1.659(11) Å and the average TcS distance 2.38(2) Å. The average cis STcS, trans STcS and OTcS angles are respectively 82.7(6)°, 138.4(3)° and 110.8(4)°.     

Synthesis and spectroscopic properties of CpRuCl(R-DAB(4e)) and CpRuCo(CO)3(R-DAB(6e)). Part XVII. X-ray structure determination of CpRuCo(CO)3(t-Bu-DAB(6e))

CpRuCl(PPh₃)₂ reacted with excess R-DAB in refluxing toluene to give CpRuCl(R-DAB(4e)) (1a: R = i-Pr; 1b: R = t-Bu; 1c: R = neo-Pent; 1d: R =p-Tol). ¹H NMR and ¹³C NMR spectroscopic data indicated that in these complexes the R-DAB ligand is bonded in a chelating 4e coordination mode.Reaction of 1a and 1b with one equivalent of [Co(CO)₄]⁻ afforded CpRuCo(CO)₃(R-DAB(6e)) (2a: R = i-Pr; 2b: R = t-Bu). The structure of 2b was determined by a single crystal X-ray structure determination. Crystals of 2b are monoclinic, space group P2₁/n, with four molecules in a unit cell of dimensions: a = 16.812(4), b = 12.233(3), c = 9.938(3) Å and β = 105.47(3)°. The structure was solved via the heavy atom method and refined to R = 0.060 and R_w = 0.065 for the 3706 observed reflections. The molecule contains a RuCo bond of 2.660(3) Å and a cyclopentadienyl group that is η⁵-coordinated to ruthenium [RuC(cyclopentadienyl) = 2.208(3) Å (mean)]. Two carbonyls are terminally coordinated to cobalt (CoC(1) = 1.746(7) and CoC(2) = 1.715(6) Å) while the third is slightly asymmetrically bridging the RuCo bond (RuC(3) = 2.025(6) and CoC(3) = 1.912(6) Å). The RuC(3)O(3) and CoC(3)O(3) angles are 138.4(5)° and 136.5(5)°, respectively. The t-Bu-DAB ligand is in the bridging 6e coordination mode: σ-N coordinated to Ru (RuN(2) = 2.125(4) Å), μ₂-N′ bridging the RuCo bond and η²-CN coordinated to Co (RuN(1) = 2.113(5), CoN(1) = 1.941(4) and CoC(4) = 2.084(5) Å). The η²-CN′ bonded imine group has a bond length of 1.394(7) Å indicating substantial π-backbonding from Co into the anti-bonding orbital of this CN bond.¹H NMR spectroscopy indicated that 2a and 2b are fluxional on the NMR time scale. The fluxionality of 6e bonded R-DAB ligands is rarely observed and may be explained by the reversible interchange of the σ-N and η²-CN′ coordinated imine parts of the R-DAB ligand.     

Metal—phenoxyalkanoic acid interactions. Part 14. The crystal and molecular structures of diaquabis(4-fluorophenoxyacetato)copper(II) bis(4-fluorophenoxyacetic acid)dihydrate and tetra-μ-(4-fluorophenoxyacetato-0,0′)-bis[(2-aminopyrimidine)copper(II)]

The crystal structures of two copper(II) complexes of 4-fluorophenoxyacetic acid (4-FPAH) have been determined by X-ray diffraction. [Cu(4-FPA)₂(H₂O)₂]·2(4-FPAH)·2H₂O (1) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 14.808(2), b = 9.832(2), c = 6.847(2) Å, α = 87.77(2), β = 98.41(2), γ = 112.33(2)° and was refined to a residual of 0.038 for 1697 ‘observed’ reflections. The coordination sphere in this complex is tetragonally distorted octahedral comprising two waters [CuO, 1.940(3) Å], two unidentate carboxylate oxygens [CuO, 1.942(2) Å] and two ether oxygens [CuO, 2.471(2) Å]. Two adducted [4-FPAH] acid molecules are linked to the un-coordinated oxygens of the acid ligands by hydrogen bonds [2.547(4) Å]. [Cu₂(4-FPA)₄(2-aminopyrimidine)₂] (2) is triclinic, space group P1 with Z = 1 in a cell of dimensions a = 12.688(2), b = 11.422(2), c = 7.951(1) Å, α = 78.74(1), β = 107.51(1), γ = 75.78(1)°, and was refined to a residual of 0.042 for 2683 ‘observed’ reflections. (2) is a centrosymmetric tetracarboxylate bridged dimer with four similar CuO (equatorial) distances [1.967–1.987 Å; 1.977(3) Å mean] and the axial position occupied by the hetero nitrogen of the 2-aminopyrimidine ligand [CuN, 2.176(3) Å]. The Cu---Cu separation is 2.710(1) Å. Crystal data are also presented which confirm the isostructurality of complex (2) with [Cu₂(phenoxyacetate)₄(2-aminopyrimidine)₂], the Co^II, Mg^II and Mn^II4-fluorophenoxyacetate complexes with their phenoxyacetic and 4-chlorophenoxyacetic acid analogues, and of Cd^II4-fluorophenoxyacetate with Cd^II and Zn^II phenoxyacetates.     

Comparative structural studies of the first row early transition metal(III) chloride tetrahydrofuran solvates

Two compounds of empirical formula MCl₃- (THF)₃, M = V and Cr, have been characterized by single crystal X-ray studies. The VCl₃(THF)₃ molecule, which has a mer octahedral stereochemistry, crystallizes in the monoclinic space group P2₁/c with a= 8.847(2),b= 12.861(5),c= 15.134(3) Å, β = 91.94(2)°, V = 1721(1) ų and Z = 4. The V-Ci(1) and V-CI(2) distances have a mean value of 2.330 [3] Å while V-CI(3) = 2.297(2) Å, The VO(1) and VO(2) distances have a mean value of 2.061[8] Å while V-O(3) = 2.102(3) Å cis ClVCl angles average 92.0[5]° and cis OVO angles average 86.2[2]° . The isostmctural complex, CrCl₃(THF)₃, has a crystal structure made up of discrete octahedral mer-CrCl₃(THF)₃ molecules with the following unit cell dimensions (space group P2₁/c): a = 8.715(1), b= 12.786(3), c = 15.122(3) Å, β = 92.15(1)°, V = 1684(1) ų and Z = 4. The CrCl(1) and CrCl(2) distances have a mean value of 2.310131 Å while CrCl(3) = 2.283(2) Å. The CrO(1) and CrO(2) distances have a mean value of 2.0101171 Å while CrO(3) = 2.077(4) Å. cis ClCrCl angles average 90.9[4]° and cis OCrO angles average 86.1 [2]°. The structures of these two octahedral complexes and those previously reported for ScCl₃(THF)₃ and TiCl₃(THF)₃ are compared and certain general trends are discussed.     

Crystal structure of [Sm(OPMePh2)4I2]I. A cationic octahedral complex of samarium(III)

The crystal structure of [Sm(OPMePh₂)₄I₂]I, 1, was determined by X-ray diffraction and refined anisotropically to a final R value of 0.067 from 3040 reflections with I>3.0σ(I). The space group was P2/a and Z=2. The unit cell dimensions were: a= 17.777(6), b=13.559(2), c=11.656(4) Å, α=γ= 90.0 and β=97.25(3)°. The cation geometry was octahedral with the Sm(III) bonded to two mutually trans I⁻ ions and four OPMePh₂ groups. A third non-bonded I⁻ was present elsewhere in the cell. The SmI and SmO distances were 3.077(1) and 2.27(1) Å respectively. Two of the SmOP angles were 172.1(6)° and the other two were 162.0(6)°.     

Syntheses,structures and ligand dissociation kinetics of Vitamin B12 model compounds with exceptionally poor electron donating groups,LCo(DH)2CHX2 (X = Cl or Br)

The syntheses and ligand dissociation kinetics of vitamin B₁₂ model compounds LCo(DH)₂CHX₂ with X = Cl and Br and L = different neutral N- and P- ligands are reported together with the crystal structures of the CHCl₂ derivatives with L = py (1) and 1,5,6-trimethylbenzimidazole, Me₃Bzm (2). Compound 1 crystallizes in the space group P2₁/n with cell parameters a = 9.617(1), b = 12.601(2), c = 15.586(2) Å, β = 95.44(1)°; 2 crystallizes in the space group P1 with cell parameters a = 8.867(2), b = 10.719(2), c = 13.345(2) Å, α = 94.81(2), β = 90.89(1), γ = 105.63(2)°. The two structures were solved by Patterson and Fourier methods and refined by least-squares methods to final R values of 0.037 (1) and 0.036 (2), using 3474 (1) and 4435 (2) independent reflections.The axial NCoC fragment is characterized by CoN and CoC distances of 2.045(2) and 1.995(2) Å in 1 and 2.043(2) and 1.983(2) Å in 2, respectively. The CoC bond lengths have the smallest values so far reported in both py and Me₃Bzm alkylcobaloximes.The displacement of the L ligand followed SN1 LIM behaviour and the corresponding rate constants depend upon the nature of L and vary in CHCl₂ derivatives from 2.42 X 10⁻¹ s⁻¹ for 2-aminopyridine to 1.99 X 10⁻⁵ s⁻¹ for P(OMe)₃. For fewer CHBr₂ analogs the rate constants were smaller.Kinetic results confirm previous findings that the donating ability of CHBr₂ is less than that of CHCl₂, although the electronegativity of Cl and Br species would suggest an opposite trend. Some relationships between kinetic and structural properties are discussed.     

Three coordination modes of the pentadentate ligand 2,6-diacetylpyridinedisemicarbazone

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Cr(NO₃)₃·9H₂O and forms two kinds of complexes. At pH=3, the ligand is singly-deprotonated and crystals of [Cr- (DAPSCH)(H₂O)₂](NO₃)₂·H₂O (Ia) are obtained. Evaporation of a solution at pH=0, yields crystals of [Cr(DAPSC)(H₂O)₂](NO₃)₃·2H₂O (II) in which the ligand is fully protonated. The reaction of DAPSC with UO₂(O₂CCH₃)₂ in methanol, followed by crystallization of the product from DMSO yields crystals of [UO₂(DAPSC2H)(H₂O)]·2DMSO (III) in which the ligand is fully deprotonated. Compound Ia is monoclinic, space group P2₁/n with a=11.746(1), b=14.752(2), c=11.866(1) Å,β=105.53(2)°, V= 1981(1) ų and Z=4. Compound II is monoclinic, space group, P2₁/n with a=38.000(3), b= 14.939(2), c=8.233(1) Å, β=96.12(2)°, V= 4647(1) Å and Z=8. Compound III is monoclinic, space group P2₁/n with a=18.048(2), b=15.207(2), c=8.842(1) Å,β=97.72(2)°, V=2405(1) ų and Z=4. The structures were refined using 2084, 4169 and 2516 reflections to R values of 4.4%, 7.8% and 4.8% respectively.     

Syntheses of iron(III) aroyl hydrazones containing pyridoxal and salicylaldehyde. The crystal and molecular structure of two iron(III)-pyridoxal isonicotinoyl hydrazone complexes

Iron(III) complexes of three aroyl hydrazones, pyridoxal isonicotinoyl hydrazone (H₂pih), pyridoxal benzoyl hydrazone (H₂pbh), and salicylaldehyde benzoyl hydrazone (H₂sbh), were synthesized and characterized. In aqueous medium at pH 7, [Fe(pih)(Hpih)]·3H₂O is formed. In acidic methanol, a 1:1 ligand-to-metal complex is formed, [FeCl₂(H₂pih)]Cl (1), whereas in aqueous medium at low pH cis-[FeCl₂(H₂pih)(H₂O)]Cl·H₂O (2) is formed. Compounds 1 and 2 are high-spin d⁵ with μ_eff = 5.88 μ_B and 5.93 μ_B (298 K). The crystal structures of 1 and 2 show that H₂pih acts as a tridentate neutral ligand in which the phenolic and hydrazidic protons have shifted to the pyridine nitrogen atoms. The co- ordination polyhedron of 1 is ‘square’ pyramidal, whereas that of 2 is pseudo-octahedral. Compound 1 is triclinic, space group P$\text{l}$, with a = 12.704(2) Å, b = 8.655(2) Å, c = 8.820(2) Å, α = 105.42(1)°, β = 89.87(1)°, γ = 107.60(1)°, V = 888 ų, and Z = 2; 2 is monoclinic, space group P2₁/c, with a = 15.358(4) Å, b = 7.304(3) Å, c = 17.442(4) Å, β = 101.00(2)°, V = 1921 ų, and Z = 4.     

Synthesis and characterization of technetium(V) complexes with tridentate schiff base ligands. X-ray crystal structure of chloro[N-(2-hydroxyphenyl)salicylideneiminato]oxotechnetium(V)

Five-coordinate technetium(V) complexes of the form TcO(L)Cl where L is one of the two tridentate Schiff base ligands N-(2-oxidophenyl)salicylideneiminate or N-(2-mercaptophenyl)salicylideneiminate have been synthesized and characterized. These neutral complexes precipitate from methanol upon reaction of the Schiff base ligand with TcOCl₄^?. A single crystal X-ray structure determination shows that the chloro [[N-(2-oxidophenyl)salicylideneiminato](2?)-N,O,O′]oxotechnetium(V) complex, [TcO(C₁₃H₉NO₂)Cl], formula weight 362, has a distorted square pyramidal coordination geometry with the oxo ligand in the axial position. The steric requirements of the oxo group cause the Tc atom to be displayed 0.67 Å out of the mean equatorial plane of the other four donor atoms. This complex crystallizes in the monoclinic space group P2₁/a with a = 13.423(6) Å, b = 12.570(5) Å, c = 7.769(3) Å, β = 106.53(5)°, V = 1256.7(9) ų, and Z = 4. The structure has been refined to R = 0.047 for 1775 observed reflections.     

The tungsten-tungsten triple bond. XV. Synthesis,structure and reactivity of 1,2-W2[CH(SiMe3)2]2(NMe2)4: the remarkable inertness of a sterically-encumbered tungsten-amido complex

Addition of 1,2-W₂Cl₂(NMe₂)₄(W≡W) to a toluene slurry of LiCH(SiMe₃)₂(2 equiv) results in the formation of 1,2-W₂[CH(SiMe₃)₂]₂(NMe₂)₄(W≡W) (I) in 79% isolated yield. Compound I has been characterized by ¹H and ¹³C NMR, IR, elemental analysis and single-crystal X-ray diffraction. The molecule exists exclusively in the gauche conformation in solution and in the solid state with WW = 2.320(1) Å. Compound I is very sterically encumbered as evidenced by: (1) large WWC angles, 110°, at the disyl ligand; (2) skewing of the NC₂ planes of the NMe₂ ligands off the WW vector; (3) anomalously large barriers to WNM₂ bond rotation in solution; (4) the inertness of I towards CO₂ and alcohols. However, compound I reacts with acetic anhydride to form 1,2-W₂[CH(SiMe₃)₂]₂(O₂CMe)₄(W≡W) (II) in 31% isolated yield. Compound II has been characterized by ¹H and ¹³C NMR, IR, and elemental analysis. The mechanistic implications of these studies with regard to alcoholysis and CO₂ insertion reactions of other 1,2-W₂R₂(NMe₂)₄ compounds are discussed. Crystal data for 1,2-W₂[CH(SiMe₃)₂]₂(NMe₂)₄ at −140°C: space group P2₁/n, a = 12.555(3), b = 18.699(5), c = 15.214(4) Å, β = 95.24(1)° and Z = 4.     

The crystal and molecular structures of dichloro [N,O-(D,L)-diaminopropionic acid] platinum(II) and Dichloro [N,O-(L)-lysine] platinum(II) monohydrate

K₂PtCl₄ reacts with L-lysine and with D,L-diaminiopropionic acid (Dap) forming the neutral complexes [PtCl₂(N,O-Lys)]·H₂0 (1) and [PtCl₂(N,O-Dap)], (2) respectively.Compound 1 is monoclinic, space group P2₁ with a = 11.262(3), b = 11.041(2), c = 9.690(2) Å, β = 102.07(5)°, V = 1178(1) ų and Z = 4. Compound 2 is monoclinic, space group P2₁/n with a = 8.777(1), b = 10.615(2), c = 7.947(1) Å, β = 94.98(3)°, V = 738(1) ų and Z = 4. In both compounds, the zwitterionic ligands form an N,O-five membered chelate with the platinum atom. Structures 1 and 2 were refined to R values of 3.3% and 6.3% respectively.     

The crystal structures of four models for the binding to DNA of cisplatinum derivatives containing a bidentate tertiary diamine

The compounds cis-[(TMED)Pt(9-MeG)₂](PF₆)₂· 2H₂O (1), cis-[(TMED)Pt(9-EtG)₂](ClO₄)₂·2H₂O(2). cis-[(TMED)Pt(DMX)₂](PF₆)₂·4H₂O (3) and cis-[(TMED)Pt(TMX)₂](PF₆)₂·xH₂O (x ≈ 4) (4), where TMED = N,N,N′,N′-tetramethylethylenediamine, 9-MeG = 9-methylguanine, 9-EtG = 9-ethylguanine, DMX = 1,3-dimethylxanthine and TMX = 1,3,9-trimethylxanthine, have been prepared and structurally characterized by X-ray methods. Compound 1 crystallises in space group Pn, with a = 10.675(1), b = 12.970(1), c = 12.016(1) Å, β = 97.05(1)°, Z = 2. Compound 2 crystallizes in space group Pbca, with a = 13.886(1), b = 31.742(4), c = 14.958(2) Å, Z = 8. Compound 3 crystallizes in space group C2/c, with a = 37.557(4), b = 12.215(2), c = 15.823(3) Å, β = 90.47(1)°, Z = 8. Compound 4 cyrstallises in the space group C2/c, with a = 38.516(5), b = 12.078(2), c = 16.219(2) Å, β = 97.88(1)°, Z = 8. Compounds 3 and 4 are structurally similar. Each [(TMED)Pt(Base)₂]²⁺ cation shows square-planar coordination to Pt with the two independent purine ligands coordinated through N7 and arranged in a head-to-tail conformation. The structures are compared with each other and with related compounds in terms of their base/base and base/coordination plane dihedral angles, and their different crystalline environments.     

Preparation,properties and crystal structures of nickel(II) complexes with acyclic schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane or 3,3′-diamino-N-methyl-dipropylamine

Nickel(II) complexes with the compartmental Schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane (H₂L¹) or 3,3′-diamino-N-methyl-dipropylamine (H₂L²) were synthesized, and the crystal structures of [Ni(L¹)- (py)₂] and [Ni(L²)(dmf)]·H₂0 were determined by X-ray crystallography.Ni(L¹)(py)₂ is monoclinic, space group C2/c, with a= 18.457(6), b = 11.116(7), c= 16.098(6) Å, and β = 115.79(5)°; D_c = 1.49 g cm⁻³ for Z = 4. The structure was refined to the final R of 6.9%. The molecule has C₂ symmetry. The nickel atom is six-coordinated octahedral. Selected bond lengths are: NiO 2.04(1) Å, NiN (L¹) 2.08(1) Å, NiN(py) 2.17(1) Å.[Ni(L²)(dmf)]·H₂O is monoclinic, space group P2₁/n, with a = 17.329(6), b = 13.322(7), c = 12.476(7) Å and β = 95.43(5)°; D_c = 1.45 g cm⁻³ for Z = 4. The structure was refined to the final R of 5.1%. The nickel atom is bonded in the octahedral geometry to the bianionic pentadentate ligand L² and to one molecule of dimethylformamide. Selected bond lengths are: NiO (charged) 2.063(3) Å (mean value), NiO (neutral) 2.120(3) Å, NiN (planar) 2.050(3) Å (mean value), NiN (tetrahedral) 2.177(3) Å.     

Organocobalt B12 Models. Structures of trans-bis(glyoximato)(alkyl)(pyridine)cobalt(III), with Alkyl = Me,Et, i-Pr

The crystal structures of the organocobalt complexes, pyCo(GH)₂Me(1), pyCo(GH)₂Et(2) and pyCo(GH)₂Prⁱ(3) (py = pyridine, GH = monoanion of glyoxime) are reported. Compound (1) crystallizes in the space group P2₁2₁2₁ with cell parameters a = 8.508(1), b = 13.586(2) and c = 11.614(6) Å; (2) crystallizes in the space group P2₁2₁2₁ with cell parameters a = 8.448(4), b = 12.164(2) and c = 13.651(2) Å; (3) crystallizes in the space group P2₁/c with cell parameters a = 8.443(7), b = 12.913(2), c = 14.341(2) Å and β = 92.86(4).The three structures have been solved by Patterson and Fourier methods and refined by least squares methods to final R values of 0.045(1), 0.068(2) and 0.057(3) using 1819(1), 1653(2) and 1582(3) independent reflections. The pyCoalkyl fragment shows significant variation of CoN and CoC bond lengths. The latter increase from 2.003(4) to 2.084(9) Å following the increase of the alkyl bulk. The CoN(py) distances increase from 2.064(3) to 2.101(6) Å with the increasing σ-donor power of the alkyl group trans to pyridine. In comparison with cobaloximes having the same axial ligands, pyCo(DH)₂alkyl (DH = monoanion of dimethylglyoxime) does not show significant differences on the pyCo alkyl fragment. CoN axial bond lengths and exchange rates of the axial neutral ligand are consistent for the two series, although changes in bond lengths are detected only when rate constants are from two to three orders of magnitude different.     

Metal-phenoxyalkanoic acid interactions. Part 15. The crystal structures of diaquabis(phenoxyacetato)cadmium(II) and catena-μ-[aquabis(phenoxyacetato-O)lead(II)-bis(phenoxyacetato)lead(II)]

The crystal structures of the cadmium(II) and lead(II) complexes of phenoxyacetic acid (PAH) have been determined by single crystal X-ray diffraction techniques. The cadmium complex, [Cd(PA)₂(H₂O)₂] (1), space group C2, with Z = 2 in a cell of dimensions, a = 11.801(2), b = 5.484(1), c = 13.431(3) Å, β = 100.87(2)°, possesses a distorted trapezoidal bipyramidal coordination around the metal atom, involving two water oxygens [2.210(5) Å] and four carboxyl oxygens from two symmetrical bidentate phenoxyacetate ligands [2.363(4), 2.365(4) Å] with Cd lying on the crystallographic two- fold axis. The lead complex, [Pb₂(PA)₄(H₂O)]_n(2) is triclinic, space group P$\text{1}$, Z = 2, with a cell of dimensions, a = 10.135(4), b = 10.675(3), c = 19.285(9) Å, α = 114.66(3), β = 91.94(3) and γ = 114.99(3)°. (2) is a two-dimensional polymer with a repeating dimer sub-unit. The first lead [Pb(1)] has an irregular MO₈ coordination [2.34?2.96(2) Å: mean, 2.63(2) Å] involving the water molecule, two oxygens from an asymmetric bidentate carboxylate group, two from a bidentate chelate [O(ether), O(carboxylate)] group and three from bridging oxygens, one of which also provides a polymer link to another symmetry generated lead. The second lead [Pb(2)] is irregular seven-coordinate [PbO, 2.48?2.73(2) Å: mean, 2.61(2) Å] with three bonds from the bridging groups, two from an unsymmetrical bidentate carboxylate (O, O′) group and one from a second carboxyl group which also bridges two Pb(2) centres in the polymer.     

A new hydroxo-bridged thorium(IV) dimer: Preparation and structure of di-μ-hydroxo-bis[aquanitrato(2,6-diacetylpyridinedisemicarbazone)thorium(IV)] nitrate tetrahydrate

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Th(NO₃)₄ in ethanolwater mixture and a di-μ-hydroxo Th(IV) dimer is formed. The compound [Th₂(OH)₂(DAPSC)₂(NO₃)₂(H₂O)₂](NO₃)₄·4H₂O (I) is monoclinic, space group P2₁/n with a = 10.705(1), b = 19.008(2), c = 11.782(1) Å, β = 107.82(2)°, V = 2282(1) ų and Z = 2. Detailed X-ray structural analysis showed that each thorium atom in the complex is coordinated to one pentadentate DAPSC ligand, which is subjected to a considerable distortion, one bidentate nitrate group, one water ligand and two bridging hydroxo groups. The coordination number is ten and the best presentation of the polyhedron is that of a distorted bicapped square antiprism. The ThTh separation is 4.0181(6) Å and the average ThO(H) bridge is 2.366 Å. The structure was refined using 3185 reflections to an R value of 5.0%.