The 1H NMR spectrum of the carbene complex shown below shows two peaks of equal intensit...

The ¹H NMR spectrum of the carbene complex shown below shows two peaks of equal intensity at 40 °C. At –40 °C, the NMR shows four peaks, two of a lower intensity and two of a higher intensity. The solution may be warmed and cooled repeatedly without changing the NMR properties at these temperatures. Account for this NMR behavior.