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Monomer−Dimer Equilibria of Oxo/Imido Complexes of Heptavalent Rhenium: Theoretical and Spectroscopic Investigations
Author(s) -
Gisdakis Philip,
Rösch Notker,
Bencze Éva,
Mink Janos,
Gonçalves Isabel S.,
Kühn Fritz E.
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200104)2001:4<981::aid-ejic981>3.0.co;2-f
Subject(s) - chemistry , dimer , rhenium , density functional theory , crystallography , monomer , steric effects , computational chemistry , photochemistry , stereochemistry , inorganic chemistry , organic chemistry , polymer
Mixed oxo/imido derivatives of methyltrioxorhenium(VII) form dimers in the solid state at ambient temperature. Density‐functional calculations show that the dimerization is exothermic. The most stable derivatives were calculated to display a pseudo trigonal‐bipyramidal coordination with two bridging oxygen centers and the methyl groups in a trans arrangement. This configuration is energetically more favored than a cis arrangement of the methyl groups and a pseudo square‐pyramidal structure at the metal centers. In the case of methyltrioxorhenium(VII), the dimerization is slightly endothermic, even for the optimal dimeric structure, so that dimers cannot be isolated. However, there is evidence for the transient existence of oxygen bridges between methyltrioxorhenium(VII) in solution. For mixed imido/oxo species, oxygen bridging is observed in all cases of dimerization; results of thermogravimetric/mass spectrometric studies demonstrate that these bridging dimers are weakly bound. From vibrational spectroscopic analysis, there is no evidence for nitrogen‐bridged homologues. The density‐functional calculations show that imido groups form bridges only in the case of sterically undemanding ligands. However, these complexes are too unstable to be isolated.