Oxygen-17 nuclear magnetic resonance spectroscopy and iridium and rhodium molecular oxygen complexes

Abstract

The ¹⁷O₂ complexes of IrCOX(PY₃)₂(X = Cl or I, Y = Ph; X = Cl, Y = C₇H₇) were prepared and their continuous-wave ¹⁷O n.m.r. spectra were recorded for chloroform solutions. No resonance attributable to bound ¹⁷O₂ could be detected 20,000 p.p.m. up- and down-field from resonance of H₂¹⁷O. Failure to observe the ¹⁷O₂ resonance could not be attributed to (i) few nuclei, (ii) dilution of bound ¹⁷O₂ by ¹⁶O₂, (iii) the presence of paramagnetic impurities, or (iv) rapid exchange between free para- and bound dia-magnetic oxygen. Similarly, the ¹⁷O resonance of IrCOl[P(C₇H₇)₃]₂S¹⁷O₄ could not be detected, which suggests that Vaska type complexes tumble at a rate which broadens the resonances beyond detection.