Structure and Reactivity of Earlyminus signLate Heterobimetallic Complexes.

Chemistry of Transition Metal Cyanide Compounds: Modern Perspectives

A strategy to enable reactivity analogous to oxidative addition is presented for d(0) transition-metal complexes. The reaction of the redox-active ligand 2,4-di-tert-butyl-6-tert-butylamidophenolate (ap) with ZrCl(4)(THF)(2) affords the new complex Zr(IV)(ap)(2)(THF)(2). This compound is formally zirconium(IV) and contains no d electrons; however, exposure of Zr(IV)(ap)(2)(THF)(2) to chlorine gas results in swift chlorine addition at the zirconium metal center via one-electron oxidation of each ap ligand. The diradical product, Zr(IV)Cl(2)(isq)(2) (isq = 2,4-di-tert-butyl-6-tert-butyliminosemiquinone), has been characterized by X-ray crystallography, electron paramagnetic resonance spectroscopy, and SQUID magnetometery.

"Oxidative addition" to a Zirconium(IV) redox-active ligand complex.

The new complex, [Zr(pda)2]n (1, pda2- = N,N'-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi2 with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ZrX2(disq)2 (3, X = Cl, Br, I; disq- = N,N'-bis(neo-pentyl)-ortho-diiminosemiquinonate) in which each redox-active ligand has been oxidized by one electron. The oxidation products 3a-c have been structurally characterized and display an unusual parallel stacked arrangement of the disq- ligands in the solid state, with a separation of approximately 3 A. Density functional calculations show a bonding-type interaction between the SOMOs of the disq- ligands to form a unique HOMO while the antibonding linear combination forms a unique LUMO. This orbital configuration leads to a closed-shell-singlet ground-state electron configuration (S = 0). Temperature-dependent magnetism measurements indicate a low-lying triplet excited state at approximately 750 cm-1. In solution, 3a-c show strong disq--based absorption bands that are invariant across the halide series. Taken together these spectroscopic measurements provide experimental values for the one- and two-electron energies that characterize the pi-stacked bonding interaction between the two disq- ligands.

π•−π• Bonding Interactions Generated by Halogen Oxidation of Zirconium(IV) Redox-Active Ligand Complexes

Zufallsentdeckung am beispiel rhenium: Oxo-komplexe in hohen und niedrigen oxidationsstufen

Metal-metal multiple bonds. 5. Molecular structure and fluxional behavior of tetraethylammonium μ -cyano-bis(cyclopentadienyldicarbonylmolybdate)(Mo-Mo) and the question of semibridging carbonyls.

The synthesis of Cp/sub 2/Mo/sub 2/(CO)/sub 4/(..mu..-Cl)(Cl) (6), Cp/sub 2/Mo/sub 2/(CO)/sub 4/(..mu..-H)(..mu..-I) (8), and Cp/sub 2/Mo/sub 2/(CO)/sub 4/(..mu..-I)/sub 2/ (2) is described. Complex 6 is best prepared from Cp/sub 2/Mo/sub 2/(CO)/sub 4/ (1) and PhICl/sub 2/ or HCl in toluene. Complex 8 is formed from 1 and HI. Excess HI converts 8 to the diiodide 2. Reaction of 2 with aluminum hydrides gives 8, which in turn reacts to give H/sub 2/ and 1. The XPS of 6 shows two types of chlorine in a 1:1 ratio with 2P/sub 3///sub 2/ ionization energies of 198.8 and 197.6 eV consistent with bridging and terminal positions, respectively. The different geometrical isomers that are exhibited by the dihalides are discussed. The structures of 2 and 8 were determined by X-ray crystallography. For 2, the violet isomer forms crystals in the triclinic system, a, b, c = 6.882 (1), 10.196 (2), 6.856 (1) angstrom; ..cap alpha.., ..beta.., ..gamma.. = 86.08 (1), 113.83 (1), 102.52 (1)/sup 0/, V = 429.5 (1) angstrom/sup 3/, Z = 1, space group P1, rho(calcd) = 2.62 g/cm/sup 3/. The structure was refined with 1702 reflections with I > 3sigma(I) to final R values of R/sub 1/ = 0.063 andmore » R/sub 2/ = 0.073. The bridging hydrogen was not located. Selected interatomic distances (angstrom) and bond angles follow: Mo-Mo = 3.310 (2), Mo-I = 2.760 (1); MoIMo = 73.70 (4), IMoMo = 53.15 (av). The nature of the bridging Mo(..mu..-H)(..mu..-X)Mo system is discussed in an EHMO framework, and the significant tilt of the Cp groups is ascribed to a trans influence propagated in the sigma(Mo-CO) and ..pi..(Mo-Cp) bonding orbitals.« less

Metal-metal multiple bonds. 10. Electrophilic additions of halogens and hydrogen halides to the molybdenum-molybdenum triple bond in dicyclopentadienyldimolybdenum tetracarbonyl

Air oxidation of the tricarbonylcyclopentadienylmolybdate(1-) anion. Molecular structure of the (.eta.2-carbonato)dicarbonylcyclopentadienylmolybdenum(II) anion, CpMo(CO)2(.eta.2-O2CO)-

Kyoung R. Han

Papers

Metal-metal multiple bonds. 5. Molecular structure and fluxional behavior of tetraethylammonium μ -cyano-bis(cyclopentadienyldicarbonylmolybdate)(Mo-Mo) and the question of semibridging carbonyls.

Metal-metal multiple bonds. 10. Electrophilic additions of halogens and hydrogen halides to the molybdenum-molybdenum triple bond in dicyclopentadienyldimolybdenum tetracarbonyl

Air oxidation of the tricarbonylcyclopentadienylmolybdate(1-) anion. Molecular structure of the (.eta.2-carbonato)dicarbonylcyclopentadienylmolybdenum(II) anion, CpMo(CO)2(.eta.2-O2CO)-