((BuO)-O-t)(3)Mo N and W-2(OBut)(6)(M M) react in hydrocarbons to form Mo-2(OBut)(6)(M M) and ((BuO)-O-t)(3)W N via the reactive intermediate MoW(OBut)(6)(M M). ((BuO)-O-t)(3)W N and CH3C N-15 react in tetrahydrofuran (THF) at room temperature to give an equilibrium mixture involving ((BuO)-O-t)(3)W N-15 and CH3C N. The ((BuO)-O-t)(3)W N compound is similarly shown to act as a catalyst for N-15-atom scrambling between MeC13 N-15 and PhC N to give a mixture of MeC13 N and PhC N-15. From studies of degenerate scrambling of IN atoms involving ((BuO)-O-t)(3)W N and MeC13 N in THF-d(8) by C-13{H-1} NMR spectroscopy, the reaction was found to be first order in acetonitrile and the activation parameters were estimated to be Delta H-not equal = 13.4(7) kcal/mol and Delta S-not equal = -32(2) eu. A similar reaction is observed for ((BuO)-O-t)(3)Mo N and (CH3CN15)-N-not equal upon heating in THF-d(8). The reaction is suppressed in pyridine solutions and not observed for the dimeric [((BuMe2SiO)-Me-t)(3)W N](2). The reaction pathway has been investigated by calculations employing density functional theory on the model compounds (MeO)(3)M N and CH3C N where M = Mo and W. The transition state was found to involve a product of the 2 + 2 cycloaddition of M N and C N, a planar metalladiazacyclobutadiene. This resembles the pathway calculated for alkyne metathesis involving (MeO)(3)W CMe, which modeled the metathesis of ((BuO)-O-t)(3)W CBut. The calculations also predict that the energy of the transition state is notably higher for M = Mo relative to M = W.