Christian Robl

Water clustering in the zeolite-like channel structure of Na2Zn[C6H2(COO)4]·9H2O

Colorless single crystals of Na2Zn[C6H2(COO)4]·9H2O were obtained in aqueous silicagel. They crystallise in the monoclinic space group P21n with a=1092.6(1), b=1391.7(1), c=1312.2(1) pm and β=102.14(1)O. Trinuclear units consisting of two facesharing Na+ coordination octahedra linked by a common corner to the Zn2+ coordination tetrahedron are connected by [C6H2(COO)4]4− anions to yield a three-dimensional framework with wide zeolite-like channels extending parallel to [100] and accomodating water molecules associated to clusters by intermolecular hydrogen bonds. Attempts to remove these water molecules caused the crystal structure to be destroyed.

Alkaline-earth squarates III.CaC4O4 · 2.5H2O, a novel polymer complex with zeolitic properties (1)

During the reaction CaC4O4 · 2.5H2OCaC4O4 · 1H2O + 1.5H2O single crystals remain undisturbed and lattice dimensions practically identical both in the water-rich and in the partially dehydrated form. In both hydrates Ca2+ and C4O42− build up a three-dimensional framework with open channels. The zeolitic character of part of the water results in a random occupation of lattice sites.

On dicobaltpyromellitate-octadecahydrate (Co2[C6H2(COO)4]·18H2O) — A compound with the novel chain-like polyanion Co(H2O)4[C6H2(COO)4]2n−n

Abstract Red single crystals of Co 2 [C 6 H 2 (COO) 4 ]·18H 2 O were obtained in aqueous silicagel. They crystallise in the triclinic space group P1 with a=686.4(1), b=1000.0(2), c=1093.2(2) pm and α =93.00(2), β =104.86(1), γ =103.59(1) o . The crystal structure refinement converged to R g =0.0350 using 2766 X-ray diffraction intensities. Infinite chain-like polyanions extending parallel to [101] made up by Co 2+ cations and pyromellitate tetraanions with Co(H 2 O) 4 [C 6 H 2 (COO) 4 ] 2n− n stoichiometry are the prominent structural feature of Co 2 [C 6 H 2 (COO) 4 ]·18H 2 O. The Co 2+ ions of the polyanion are coordinated octahedrally by four water molecules situated in the equatorial plane of the coordination octahedron and two oxygen atoms belonging to carboxylate groups bound in trans-positions. Co(H 2 O) 2+ 6 ions are intercalated between the chains in order to compensate for the negative excess charge of the polyanions. Further water molecules not coordinated to Co 2+ stabilise the crystal structure by hydrogen bonds.

Complexes with substituted 2,5-dihydroxy-p-benzoquinones: The inclusion compounds [Y(H2O)3]2 (C6Cl2O4)3·6.6H2O and [Y(H2O)3]2 (C6Br2O4)3·6H2O

Abstract Single crystal of [Y(H 2 O) 3 ] 2 (C 6 Br 2 O 4 ) 3 ·6H 2 O and [Y(H 2 O) 3 ] 2 (C 6 Cl 2 O 4 ) 3 ·6.6H 2 O were grown in aqueous silicagel. The compounds are in principle isostructural. In Y chloranilate one additional water site is occupied as verified by X-ray single crystal structure analysis. Y 3+ is nine-coordinated by three water molecules and six oxygen atoms of the bischelating (C 6 X 2 O 4 ) 2− ions (XCl, Br). The coordination polyhedron is an only slightly distorted tri-capped trigonal prism. The connection of Y 3+ with the dianions leads to infinite, corrugated layers. The layer stacking yields cage-like cavities in which water molecules are accomodated. Hydrogen bonds interlink adjacent layers. Further hydrogen bonds involve the entrapped water molecules. DSC measurements indicated a complicated dehydration process which caused right at the start destruction of the single crystals.

Bis(ylide)-Substituted Phosphenium and Phosphonium Halides.

Abstract The bis(triphenylphosphoniumylidyl)halophosphines expected from the condensation of ylidyl dihalophosphines with trimethylsilyl ylides or of their addition to carbodiphosphoranes enter a spontaneous dissociation to yield bis(ylidyl)phosphenium halides. They are the first phosphenium salts which do not need anions of low basicity such as AlCl4−. 31P NMR spectra and, in one case, a single-crystal X-ray investigation reveal an essentially planar structure of the PCPCP skeleton with E, E-conformation. The bis(ylidyl)phosphenium halides are protonated at an ylidic carbon atom while at the same time the halide ion is re-associated to the central phosphorus atom. They add halogen or ortho quinones to the central phosphorus to yield the corresponding phosphonium ions. They are also oxidized by elemental sulfur or gray selenium resulting in bis(ylidyl)thio- and -seleno-phosphinyl halides. As can be shown by their solvent dependent 31P NMR spectra, they dissociate in polar media to yield the first examples of chalcogenoxophosphonium halides. As revealed by another X-ray structure analysis, the conjugation in a bis(ylidyl)dihalophosphonium ion is interrupted at the central phosphorus atom.

Hydrogen bonding in the chain-like coordination polymer ZnC4O4·4H2O: A neutron diffraction study

Abstract Monoclinic crystals of ZnC4O4·4H2O were grown in an aqueous silica gel: lattice constants a = 901.2(2) pm, b = 1333.6(3) pm, c = 674.6(2) pm, β = 99.33(2)°, Z = 4, space group C2 c . Anisotropic refinement on single-crystal neutron diffraction data led to Rw = 0.0294 including anharmonic thermal parameters for hydrogen atoms and oxygen atoms of the water molecules. The coordination polyhedron of Zn2− is a slightly distorted octahedron formed by four water molecules and two Osquarate atoms which are bound in the trans position to the C4 ring of the dianion (ZnO, 207.6(1)–212.6(1) pm). Infinite chains consisting of Zn2+ and C4O2−4 are the main feature of the crystal structure. Adjacent chains are connected by asymmetric hydrogen bonds between H2O and the Osquarate atoms. The squarate dianion is ideally planar. The crystallographically independent CO bond lengths are identical (2 × 125.0(1) pm) although the Osquarate atoms are differently coordinated by Zn2+ and H. The CC bond lengths are slightly different (146.4(1) and 146.7(1) pm).

Metal complexes of biologically important ligands. Part LXIV. Pentamethylcyclopentadienyl-rhodium(III) complexes with α-amino acid derivatives as bridging ligands and with several chiral metal centers: synthesis and structure of [Cp*Rh(μ-L-phenylalaninato)]3(BF4)3 and [Cp*Rh(μ-NHCOCH2NCO2CH2Ph)]2

Abstract Elimination of chloride from Cp*Rh(L-PheO)Cl with AgBF4 leads to the trinuclear complex [Cp*Rh(μ-L-PheO)]33+(BF4−)3 (2), in which the amino acidate acts both as an (N, O)-chelating and as a carboxylate bridging ligand according to the X-ray stmctural determination. Trimerization of [Cp*Rh(PheO)]+ occurs with chiral self recognition, i.e. in solution and in the crystal only diastereomers with the same configuration at the three chiral rhodium atoms (RRhRRhRRh and SRhSRhSRh) are formed. Reaction of [Cp*RhCl2]2 with carbobenzoxy glycine amide in the presence of base gives the dimeric complex [Cp*Rh(μ-NHCOCH2NCO2CH2Ph)]2 (3). X-ray diffraction showed that the two rhodium atoms with RRhSRh configuration are bridged by the deprotonated glycine amide N atom. Complexes 2 and 3 may be of interest as chiral catalysts; they catalyze the ester exchange of N,N-dimethylglycine ethylester in CD3OD.

A neutron diffraction study on hydrogen bonding in the mineral mellite (Al2[C6(COO)6] · 16H2O) at 15 K

Lattice constants for tetragonal Al2[C6(COO)6] · 16 H2O at 15 K are a = 1555.3(5) and c = 2311.0(8) pm, Z = 8, space group I41acd. Anisotropic refinement on single-crystal neutron diffraction data led to Rw = 0.039. The crystal structure is made up by barely distorted Al(H2O)3+6 octahedra linked by strong asymmetric hydrogen bonds to the [C6(COO)6]6− anions yielding a complicated three-dimensional framework. Additional water molecules not bound to Al3+ participate in hydrogen bonding as well. Hydrogen bonds involving water molecules bound to Al3+ as proton donors are markedly shorter (O ··· H2O 257.6–266.4 pm) than those with noncoordinated water molecules (271.0 and 272.4 pm). OH bond lengths corrected for thermal motion range from 99.5 up to 101.3 pm. The hexaanion has 222 symmetry with CO bonds being equal (125.5–125.7 pm) within the limits of experimental error. The OCO angles are widened up considerably (124.96 and 126.30°). The C6 ring of the anion deviates slightly, but significantly from an ideal hexagon.

Synthese und Kristallstruktur der Grignardverbindungen C5H5MgCl · O(C2H5)2 und C5Me5MgCl · O(C2H5)2

Single crystals of CpMgCl · O(C2H5)2 (I) (Cp  C5H5) and Cp★MgCl · O(C2H5)2 (II) (Cp★  C5Me5) have been prepared. In both compounds the formation of dimeric units is shown by X-ray structure determination. These symmetric dimeric species contain MgCl2Mg bridges with nearly identical MgCl distances (d= 243 pm). The Cp and Cp★ fragments are η5-coordinated to the metal atom. The average MgC-distances (d = 239 pm (bdI); 241 pm (bdII)) are significantly longer than those in MgCp2 (230 pm) and MgCp2★ (235 pm) respectively. lie MgO distances range between 205 and 208 pm.

Metallorganische Lewis-Säuren: XLIII. Reaktion des hochreduzierten Carbonylmetallats [Ir(CO)3]3- mit dem Ethylenpentacarbonylrhenium-Kation: Bildung des dreikernigen Hydrids (OC)5Re–Ir(CO)3(H)–Re(CO)5 und des trismetallierten Carbonats μ3-CO3[Re(CO)5]3+☆☆☆★

Abstract The cationic complex [η2-C2H4)Re(CO)5]+PF6− reacts with the highly reduced Ellis compound na3Ir(CO)3 to give the linear, trinuclear hydride (OC)5Re-Ir(CO)3H-Re(CO)5 (1), the structure of which has been determined by X-ray diffraction. Unexpectedly, from a solution of [(η2-C2H4)Re(CO)5]+ and [Ir(CO)3]3− exposed to air, crystals have been obtained which contain the carbonate bridged complex (μ3-CO3)[Re(CO)5]3+ReO4− (3) of wind wheel structure and the known cubane [Re(CO)3OH]4 (2 in the unit cell. Reaction of [Re(CO)4]3− and [(μ7-C7H7)Mo(CO)3]+ affords the redox product (OC)3Mo(μ6-C7H7-C7H7-μ6)Mo(CO)3 (4).