The reaction of rhenium nitrido complexes with +CPh3. Synthesis, structures and EPR spectra of rhenium imido compounds

The reactions of triphenylcarbonium hexafluorophosphate, (CPh3)(PF6), with the terminal nitrido ligands of [ReN(Et(2)dtc)(2)-(Me2PhP)] (Et(2)dtc(-) = N,N-diethyldithiocarbamate) and (Bu4N)[ReNCl4] are described. The resulting imido complexes [Re(NCPh3)(Et(2)dtc)(2)(Me2PhP)](PF6) and (Bu4N)[Re(NCPh3) Cl-4(ORe3)] have been studied by X-ray crystallography showing short rheniu m-nitrogen multiple bond lengths of 1.706(6) and 1.686(6) Angstrom, respect ively. Nevertheless, the structural trans influence due to the imido ligand is significantly smaller than that of 'N3-' which leads to a decreasing of the trans Re-S bond length by 0.24 Angstrom in [Re(NCPh3)(Et(2)dtc)(2)(Me2 PhP)](PF6). Despite the addition of the bulky +CPh3 to the nitrido ligand, the N drop Re-L-(equatorial) angles are only slightly increased in [Re(NCPh 3)(Et(2)dtc)(2)(Me2PhP)](+), whereas those in [Re(NCPh3)Cl-4-(OReO3)](-) ar e smaller compared with the values in the starting complex which may also b e attributed to the occupation of the sixth coordination position by perrhe nate. The rhenium(VI) compounds (5d(1)) [Re(NCPh3)X4Y](-) (X = F, Cl, Br, N CS; Y = X or OReO3) were studied by EPR spectroscopy indicating a noticeabl e loss of electron density in the central 'ReNX4' moiety upon addition of CPh3 to the nitrido site of the [ReNX4(5)](-,(2-)) starting complexes. The EPR parameters of mixed-ligand intermediates of the general composition [Re (NCPh3)Br4-nClnY](-) (Y = Cl, Br or OReO3) which are formed during ligand e xchange reactions are clearly correlated to the composition of the coordina tion sphere and can be used to characterize the mixed-ligand species unambi guously. (C) 2000 Elsevier Science Ltd. All rights reserved.