Multiple Bonds between Main-Group Elements and Transition Metals. 166.1 Oxo/Imido Complexes of Heptavalent Rhenium: Structures, Reactivity, and Behavior in Solution

Abstract

Mixed imido/oxo rhenium(VII) complexes, formal derivatives of methyltrioxorhenium(VII) (1) with (2,6-diisopropylphenyl)imido ligands of general formula CH3ReO3-x(NR)x (x = 1, and 2; compounds 2 and 3, respectively), have been synthesized. Their structures and behavior in solution have been studied by dynamic 1H and 17O NMR spectroscopy. In the solid state, compounds 2 and 3 display dimeric structures, as shown by X-ray crystallography. In solution, monomeric and dimeric forms exist in equilibria. At elevated temperatures, the monomers are dominant. In the solid state, the dimeric compounds are bridged by oxygen ligands, forming Re2O2 units, while in solution, nitrogen bridging is also evident. Formal replacement of all three oxo groups in 1 by (2,6-diisopropylphenyl)imido ligands leads to a compound of formula CH3Re(NR)3 (4). Complex 4 is monomeric both in solution, regardless of the temperature, and in the solid state. Ligand exchange processes take place via dimeric intermediates if organorhenium oxides...