Guanidinato and amidinato complexes of iridium(I): Synthesis, oxygen and sulfur8 reactivity, and (alkene)peroxo- and (alkene persulfidoiridium(III) intermediates

A variety of mononuclear alkene complexes, [Ir{ArNC(NR2)NAr}(cod)], and dicarbonyl complexes, [Ir{ArNC(NR2)NAr}(CO)2] (where R = Me or Et; Ar = Ph, 4-MeC6H4, 4-MeOC6H 4, 2,6-Me2C6H3 or 2,6- iPr2C6H3; and cod = 1,5-cyclooctadiene), were synthesized from the neutral N,N-dialkyl- N',N"-diarylguanidines via deprotonation and transmetalation. These complexes were fully characterized by spectroscopic techniques and single-crystal X-ray diffraction. The single-crystal structure determinations show the guanidinato(1---) ligands coordinate the low valent d8 iridium(I) center in an N,N'-chelating binding mode, and the C---N bond lengths indicate a high degree of pi-electron delocalization over the CN3 core. The 13C NMR chemical shifts of the alkene carbon atoms in the IrI(cod) complexes and the average CO stretching frequencies for the IrI(CO)2 complexes suggest that the guanidinato ligands function as stronger donors than related monoanionic, bidentate nitrogen-donor ligands.;Intermediates in the reactions of the [Ir{ArNC(NR2)NAr}(cod)] complexes with O2 were identified and characterized as (alkene)peroxoiridium(III) species, [Ir{ArNC(NR2)NAr}(cod)(O2)], using multi-dimensional NMR and IR spectroscopy. The (alkene)persulfidoiridium(III) intermediate [Ir{PhNC(NMe 2)NPh}(cod)(S2)] was identified and characterized in the reaction of [Ir{PhNC(NMe2)NPh}(cod)] with S8. It was determined that these intermediates are able to transfer oxygen or sulfur to simple organic molecules such as PPh3. The self-decay of the (alkene)peroxoiridium(III) intermediates leads to C---O bond formation and alkene oxidation, and upon addition of excess cod release of 4-cycloocten-1-one was observed.;In addition, a mononuclear alkene complex, [Ir{PhNC(Me)NPh}(cod)], and a dinuclear tetracarbonyl complex, [{Ir(CO)2}2{ mu-PhNC(Me)NPh-kappaN:kappaN'} 2], with an amidinato ligand, were synthesized and characterized. In the reaction of the IrI(cod) complex with O2, the corresponding (alkene)peroxoiridium(III) intermediate [Ir{PhNC(Me)NPh}(cod)(O 2)] was observed. The reactivity of this intermediate and its decay products is similar to that of [Ir{ArNC(NR2)NAr}(cod)(O2)], with the formation of 4-cycloocten-1-one being observed upon addition of cod.;Mononuclear (alkene)rhodium(I) complexes, [Rh{PhNC(NMe 2)NPh}(cod)] and [Rh{PhNC(Me)NPh}(cod)], and a dinuclear complex, [{Rh(nbd)} 2{mu-PhNC(NMe2)NPh-kappaN: kappaN'}2], were synthesized and characterized (where nbd = norbornadiene or bicyclo[2.2.1]hepta-2,5-diene). Investigation of the reactivity of these complexes with O2 show they react very slowly or not at all.