Thermolysis of dimethyltitanocene in the presence of internal alkynes formed the corresponding titanacyclobutenes cleanly and efficiently. This reaction was shown to be first order in dimethyltitanocene with a primary kinetic isotope effect. When diphenylacetylene was reacted with dimethyltitanocene at lower temperatures, a competitive migratory insertion process took place, forming a vinyl-substituted titanocene species. An analogous reaction with 2 equiv of nitriles formed the known 1,3-diaza-2-titana-1,4-cyclohexadiene derivatives.