Victor G. Young

Reversible cleavage and formation of the dioxygen O-O bond within a dicopper complex

A key step in dioxygen evolution during photosynthesis is the oxidative generation of the O-O bond from water by a manganese cluster consisting of M2(μ-O)2 units (where M is manganese). The reverse reaction, reductive cleavage of the dioxygen O-O bond, is performed at a variety of dicopper and di-iron active sites in enzymes that catalyze important organic oxidations. Both processes can be envisioned to involve the interconversion of dimetal-dioxygen adducts, M2(O2), and isomers having M2(μ-O)2 cores. The viability of this notion has been demonstrated by the identification of an equilibrium between synthetic complexes having [Cu2(μ-η2:η2-O2)]2+ and [Cu2(μ-O)2]2+ cores through kinetic, spectroscopic, and crystallographic studies.

New complexes of thriethanolamine (Tea): Novel structural features of [Y(TEA)2](ClO4)3·3C5H5N and [Cd(TEA)2](NO3)2

Abstract The synthesis and characterization of the triethanolamine (TEA) complexes Sc(TEA)2Cl3 (1), Y(TEA)2(ClO4)3·3C5H5N (2), Fe(TEA)2Cl3 (3), Ni(TEA)2Cl2 (4), Zn(TEA)2Br2 (5), Zn(TEA)2(NO3)2 (6), Cd(TEA)2Cl2 (7), Cd(TEA)2(NO3)2 (8), Pb(TEA)2(OAc)2 (9) and Bi(TEA)2Cl3 (10) are reported. The structures of 2 and 8, determined by X-ray diffraction, unexpectedly revealed eight-coordinate metals in both cases. Both structures adopt a distorted hexagonal bipyramidal configuration in which the atoms in the hexagonal plane alternately fall above and below the plane. In 2, the tree pyridines as well as the three perchlorates are involved only in hydrogen bonding to the OH groups of different TEA ligands, causing a novel distortion of the coordination sphere. Compound 8 represents an unusual example of the relatively rare coordination number eight for cadmium(II).

The 1,3-dimetalloallyl tri-ruthenium cluster (μ-H)Ru3(μ3-η3-CHCHCMe)(CO)9 and its PPh3 derivatives

Abstract Reactions of Ru3(CO)12 with 1,3-butadiene or cis-2-butene give the μ3-η3dimetalloallyl compound (β-H)Ru3(β3-η3-CHCHCMe)(CO)9 (2). Refluxing 2 with PPh3 gives the CO-substituted products (μ-H)Ru3(μ3--η3 CHCHCMe)(CO)8(PPh3) (3) and (μ3-H)Ru3(μ3-η3-CHCHCMe(CO)7(PPh3)2 (4). Single crystal X-ray diffraction studies of 2, 3 and 4 show that all have the dimetalloallyl unit. These investigations demonstrate that this unit is remarkably stable and might be expected to form on triangular arrays of metal atoms on metal surfaces.

Alkali and alkaline earth metal chloride complexes of triethanolamine: The structure of [Sr(TEA)2]Cl2

Abstract The little triethanolamine (TEA) complexes isolated include M(TEA)Cl where M = Li ( 1 ), Na ( 2 ), K ( 3 ), Rb ( 4 ), Cs ( 5 ) and M(TEA) 2 Cl 2 where M = Mg ( 6 ), Ca ( 7 ), Sr ( 8 ), Ba ( 9 ) . These compounds were characterized by 1H NMR, 13C NMR and mass (FAB) spectroscopies, by elemental analysis and where appropriate by 7Li and 23Na NMR spectroscopies. In our hands the constitutions of 7 and 8 differ from those reported by others. The molecular structure of 8, determined by X-ray means, reveals strontium ions bound to two tetradentate TEA molecules. Substantial hydrogen bonding to chlorides in the structure is also evident. Four out of the 20 molecules in the unit cell are also coordinated to a water molecule.

Manganese(II) complex of the ‘tripod’ ligand tris(2-benzimidazolylmethyl)amine. Seven-coordinate Mn(II) in the crystal structure

Abstract Mn(II) coordination compounds with tripodal N,N,N-tris-(2-benzimidazolylmethyl)amine (TMBA) have been synthesized and spectroscopically characterized. The crystal structure of [Mn(TMBA)(NO3)(CH3OH)](NO3)H2O has been determined. The compound crystallizes in the monoclinic space group P21/c with four formula units in a cell of dimensions a = 11.3825(2), b = 13.4338(2), c = 17.9548(3) A , β = 100.026(1)° ; final R = 0.0299, based on 4745 independent reflections. The structure indicates the complex ion has a heptacoordinate metal center with a coordination polyhedron best described as a capped octahedron. The octahedron is defined by three nitrogen atoms from the benzimidazole moieties (N(1A), N(1C) and N(1B)), the oxygen atom of the methanol O(41), and two oxygen atoms from the coordinating nitrate group O(11) and O(12). The capping ligating atom is the bridging N(1) from the TMBA ligand with a longer MnN distance of 2.551(1) A.

New group V κ-phases

Abstract New κ-phases (P. Rautala and J.T. Norton, Trans. AIME, 194 (1952) 1045; A. Harsta and S. Rundqvist, J. Solid State Chem., 70 (1987) 210) were discovered and crystallographically characterized in the Zr Ta S, Zr Nb S, Zr V S, Hf Nb S, and Hf V S systems, A κ-phase was also identified in the Hf Ta S system through Guinier powder diffraction. These compounds are the first examples of the κ-phase structure containing the Group V transition metals, Ta, Nb, and V. The Ta and Nb κ-phases exhibit the largest volumes (by about 13%) and the largest amounts of second row nonmetal per formula unit of the known κ-phases. X-ray single-crystal diffraction experiments were used to determine metal site occupancies in these κ-phases, and it was found that statistical mixing of the metals primarily on one site occurred for the Ta and Nb compounds. Refinements of the X-ray intensity data indicated that the octahedral nonmetal sites (denoted X2) are less than fully occupied by sulfur in the Ta and Nb κ-phases and less than fully occupied by oxygen in the V κ-phases. Combined neutron and X-ray powder refinements reliably determined that these nonmetal X2 sites are occupied by a mixture of sulfur, oxygen, and vacancies in the Zr Nh S and Zr Ta S κ-phases. The κ-phases in the Zr Nb S (G. Marking et al., Phys. Rev. B, 48 (1993) 16630) and Hf Nb S systems were found to be superconductors with T 2 s of 10.35 K and between 6 and 7 K respectively.