Fig. 6. (top) Excerpt of the 13C NMR spectrum for 3 showing the isocyanide resonance coupled to yttrium. (bottom) The isocyanide resonance is compared with Y–C one- and two-bond coupling constants for some representative alkynyl complexes from Teuben and Evans.34,36,37 The coupling constant observed for 3 is in the typical range for a two-bond coupling, much smaller than a typical one-bond coupling constant. Ar = 2,4,6-(iPr)3C6H2.
