C−N Coupling of Methane and Ammonia by Bimetallic Platinum−Gold Cluster Cations

Fourier transform ion-cyclotron resonance mass spectrometry is used to investigate the reactivity of mass-selected bimetallic Pt m Au n + clusters ( m + n ≤ 4) with respect to the C−N coupling of methane and ammonia. To this end, the reactions of the heterometallic carbene species Pt m Au n CH 2 + with NH 3 as well as those of the bare clusters with CH 3 NH 2 are studied. On the basis of these experiments augmented by deuterium labeling studies, structural assignments for the reaction products are proposed. Surprisingly, only the dinuclear carbene PtAuCH 2 + mediates C−N bond formation to presumably afford the aminocarbene complex PtAuC(H)NH 2 +, whereas the larger bimetallic carbene clusters mainly yield the carbide species Pt m Au n C + ·NH 3 upon reaction with NH 3 . This difference is rationalized by distinct metal−carbene binding energies. While the pure Au n + clusters do not afford C−N coupling either, they undergo degradation reactions with NH 3 and CH 3 NH 2 that are subject to pronounced even−odd size effects.