Cubane-like Structure Research Articles

Notes. Heterobimetallic clusters derived from [MS4]2–(M = Mo or W): synthesis and structural characterization of [NMe4]4[(CuCl)5Cl2WS4], a double cubane-like complex

Reaction of [NMe4]2[MS4](M = Mo or W) with CuCl (1:3.5) in CH3CN produces a hexanuclear complex anion [(CuCl)5Cl2MS4]4–. Crystals of [NMe4]4[(CuCl)5Cl2WS4] are monoclinic, space group C2/c with cell dimensions a= 21.610(4), b= 9.340(2), c= 19.570(5), β= 92.84(2)°, and Z= 4. Least-squares refinement based on 2 708 reflections with I 3σ(I) converged at R= 0.032. The anion has crystallographically imposed C2 symmetry. The crystal structure determination shows that five of the six edges of the [WS4]2– tetrahedron are co-ordinated by CuCl units forming an open double cubane-like structure; the cubic geometry is achieved by chlorine atoms.

A reactive and versatile fourteen-electron copper(I) fragment for binding carbon monoxide, isocyanides, and phosphines: synthesis, crystal structure, and reactivity of (2-methylquinolin-8-olato)copper(I) derivatives

The synthesis of the 14-electron copper(I) moiety [Cu(2Me-quin)](2Me-quin = 2-methylquinolin-8-olate) having a bent arrangement of the donor atom is reported. The reaction of CuCl with Na(2Me-quin) led to the disproportionation of copper(I) to copper(II) and copper metal, while in the presence of CO, a thermally very stable carbonyl complex [{Cu(2Me-quin)(CO)}4](2) was isolated [ν(CO)(Nujol) 2 050 cm–1]. Complex (2) has a tetranuclear cubane-like structure, with S4 symmetry, in which the coppers are bridged by the oxygen atom of the quinolinolate anion [av. Cu–O 2.04, Cu ⋯ Cu, 3.615, Cu–C 1.76 A). Carbon monoxide can be replaced in the tetranuclear structure by p-MeC6H4NC to form [{Cu(2Me-quin)(p-MeC6H4NC)}4](4)[ν(CN)(Nujol) 2 145 cm–1], which was also formed directly from CuCl, Na(2Me-quin), and p-MeC6H4NC. Reaction of PPh3 and dppe (Ph2PCH2CH2PPh2) replaced CO and led to monomeric complexes [Cu(2Me-quin)(PPh3)2](5) and [Cu(2Me-quin)(dppe)](6). Complex (2) was used as a source of dicopper(I), by treating it with dppm (Ph2PCH2PPh2) which caused loss of CO and led to the formation of [Cu2(2Me-quin)2(µ-dppm)](7). The two Cu(2Me-quin) fragments share the oxygen atom of the quinolinate ligand, forming a dimetallic fragment [Cu ⋯ Cu 2.790(2)A], where the five-co-ordination of each copper(I) is completed by one of the P donor atoms from the dppm ligand. Compound (2) catalyses the reduction of nitrosobenzene to azoxybenzene and nitroalkanes to oximes and nitriles under a pressure of carbon monoxide (60–100 atm) at temperatures from 80 to 110 °C. Compounds (2), (5), and (7) were characterized by single-crystal X-ray analysis: (2), space group P21/n(monoclinic): a= 15.591(3), b= 18.558(3), c= 15.850(3)A; β= 90.08(2), Z= 4, R 0.069 (R′= 0.076) for 1 414 observed reflections; (5), space group Pna21(orthorhombic), a= 27.478(4), b= 12.519(2), c= 11.031(3)A, Z= 4, R 0.059 for 1 920 observed reflections; (7), space group P(triclinic), a= 12.018(4), b= 17.540(4), c= 11.793(4)A, α= 90.82(3), β= 119.02(2), γ= 78.00(3)°, Z= 2, R 0.051 (R′= 0.054) for 3 876 observed reflections.

Mechanism for photosynthetic O2 evolution.

We present a mechanism for photosynthetic O2 evolution based on a structural conversion of a Mn4O6 "adamantane"-like complex to a Mn4O4 "cubane"-like complex. EPR spectral data obtained from the S2 state of the O2-evolving complex are characteristic of a Mn4O4 cubane-like structure. Based on this structure for the manganese complex in the S2 state as well as a consideration of the other evidence available on the natural system and the coordination chemistry of manganese, structures are proposed for the five intermediate oxidation states of the manganese complex. A molecular mechanism for the formation of an O--O bond and the displacement of O2 from the S4 state is easily accommodated by the proposed model. The model is discussed in terms of recent EPR, x-ray, and UV spectral data obtained from the manganese site in the photosynthetic O2-evolving complex.

Hydrogenolysis of cubane

On catalytic hydrogenation over Pd-C under normal conditions cubane (10) takes up 3 mol of hydrogen in a few hours. Bicyclo[2.2.2] octane (13) is formed as the main product, and tetracyclo[4.2.0.02,5.03,8]octane (11, secocubane) and tricyclo[4.2.0.02,5]octane (12,nortwistbrendane) have been identified as intermediates. The hydrogenolysis of dimethyl 1,4-cubane dicarboxylate, as well as cuneane derivatives, have also been studied. Results are discussed in terms of strain relief calculated by the molecular mechanics method for cubane-like structures.

Magnetic Property and Crystal Structure of Alkoxo-bridged Bi- and Tetranuclear Copper(II) Complexes with Condensation Products of 3-Ethoxymethylene-2,4-pentanedione and Amino Alcohols

Abstract Alkoxo-bridged polynuclear copper(II) complexes with condensation products of 3-ethoxymethylene-2,4-pentanedione and each of three amino alcohols, 2-aminoethanol, 3-amino-1-propanol, and 1-amino-2-propanol, were prepared and characterized by elemental analyses, infrared spectra, electronic spectra, molecular weight measurements, magnetic susceptibility measurements, and crystal structure analysis, the complexes being abbreviated as Cu(L-2), Cu(L-3), and Cu(L-2m), respectively. Cu(L-3) is a dimer, but Cu(L-2m) and Cu(L-2) are tetramers. The magnetic susceptibility of violet Cu(L-3), whose electronic spectrum exhibits a d-d band maximum at 17.7×103 cm−1, is in conformity to the Bleaney-Bowers equation with exchange integral −2J=920 cm−1. Cu(L-3) consists of alkoxo-bridged centrosymmetric binuclear units, where the geometries around the copper ion and bridged oxygen atom are planar and the angle of Cu–O–Cu is 103.6(1)°. The magnetisms of blue complexes Cu(L-2) and Cu(L-2m) exhibiting a d-d band maximum at 15.7×103 cm−1 obey the Curie Weiss law with positive Weiss constants 17 and 20 K, respectively, and are in accord with the Heisenberg model based on a tetranuclear cubane-like structure.

Copper(I) binds carbon monoxide in a cubane-like structure: chemistry and X-ray crystal structure of tetrakis[(2-methylquinolin-8-olato)-carbonylcopper(I)

Copper(I) chloride reacts with a solution of sodium 2-methylquinolin-8-olate (qNa) in tetrahydrofuran under a pressure of 60 atm of CO at 65 °C to give a tetranuclear copper(I) carbonyl complex [Cu(q)(CO)]4, (1), [ν(C–O), 2050 cm–1], having a cubane-like structure, with S4 symmetry, in which the copper atoms are bridged by the oxygen atom of the quinolinolato ligand.

Crystal structure and magnetic properties of bis{di-µ-ethoxo-bis[4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionato]dicopper(II)}

The crystal and molecular structure of the title compound has been determined by a single-crystal X-ray diffraction study. The compound crystallizes in the space group Fddd of the orthorhombic system with eight tetrameric molecules in a cell of dimensions a= 14.071(5), b= 14.294(9), and c= 49.93(3)Å. The structure has been refined to an R value of 0.076 for 1 354 independent reflections. The structure consists of D2 symmetry tetranuclear molecules in which copper ions are linked by triply bridging OEt groups. The Cu4O4 core formed by copper atoms and ethoxy-oxygen atoms has a cubane-like structure: the Cu ⋯ Cu separations are 2.977(2), 3.260(2), and 3.281 (2)Å, while the Cu–O bond lengths are 1.945(6), 1.947(6), and 2.411(7)Å the Cu–O–Cu bridging angles are 99.8(3), 97.1 (3), and 96.3(2)°. The co-ordination around each copper centre is roughly square-pyramidal. Magnetic susceptibility data (80–300 K) are interpreted in terms of the Heisenberg–Dirac–Van Vleck model. Substantial antiferromagnetic interactions (2J=–352 cm–1) are found between copper ions in the roughly planar dimeric fragments of the tetranuclear molecule, and small interactions (2J=–10 cm–1) between these fragments.