Electronic structure of dimetal bonded systems: ditungsten, dimolybdenum and diruthenium systems

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Title: Electronic structure of dimetal bonded systems: ditungsten, dimolybdenum and diruthenium systems
Author: Villagran Martinez, Dino
Abstract: This dissertation investigates three topics in the field of multiple -bonded metal chemistry . The first topic concerns the synthetic and theoretical considerations of ditungsten formamidinates and guanidinates compounds . This work presents an enhanced synthetic path to the W2 (hpp )4 molecule (Hhpp = 1 ,3 ,4 ,6 ,7 ,8 -hexahydro -2H -pyrimido[1 ,2 -a]pyrimidine ) . The reflux of W (CO )6 with Hhpp in o -dichlorobenzene at 200 oC produces W2 (hpp )4Cl2 in a one -pot reaction in 92 % yield . This compound is stable and easily stored for further use , and it can be efficiently reduced in a one -step reaction to the most easily ionized compound W2 (hpp )4 . This work also examines the electronic structure and geometry of the intermediates W2 ( ? ? ? ? -CO )2 ( ? ? ? ? - hpp )2 ( ? ? ? ?2 -hpp )2 and W2 (hpp )4Cl2 . The second topic concerns the theoretical investigation by DFT of the electronic structure of [Mo2] units bridged by oxamidate ligands or bridging hydride ions ([Mo2] = (Mo2 (DArF )3 , where DArF is the anion of a diarylformamidine ) . It is shown that the effect of the gauche conformation of the ? ? ? ? oxamidate isomers is due to steric interactions , and that the planar ? ? ? ? oxamidate isomers have an electronic structure similar to that of naphthalene when it is doubly oxidized . The [Mo2] ( ? ? ? ? -H )2[Mo2] compound shows interdimetal unit interactions between the ? ? ? ? orbitals of the two [Mo2] units . These interactions are theoretically predicted and experimentally observed by a decrease in the [Mo2] - - -[Mo2] distance with a one -electron oxidation of [Mo2] ( ? ? ? ? - H )2[Mo2] . The final topic concerns the magnetic and structural properties of two Ru2 (DArF )4Cl compounds . The compounds with Ar = p -anisyl (para ) and m -anisyl (meta ) both show different temperature dependence of their molar magnetic susceptibility , ? ? ? ? . For the para compound , there is a Boltzmann distribution between a ? ? ? ?*3 ground state and a ? ? ? ?*2 ? ? ? ?* upper state , and this is confirmed by a temperature dependence of the Ru -Ru bond length : 2 .4471 (5 ) ? ? ? ? at 23 K and 2 .3968 (5 ) ? ? ? ? at 300 K . For the meta compound , a ? ? ? ?*2 ? ? ? ?*configuration persists over the range of 23 -300 K as shown by an invariant Ru -Ru bond length and its molar magnetic susceptibility .
URI: http : / /hdl .handle .net /1969 .1 /4722
Date: 2007-04-25

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Electronic structure of dimetal bonded systems: ditungsten, dimolybdenum and diruthenium systems. Available electronically from http : / /hdl .handle .net /1969 .1 /4722 .

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