Chromium, tungsten, iron, and ruthenium complexes of the 4-membered ring diazene 3,4-diazatricyclo[4.2.1.0 2,5]non-3-ene

Abstract

The 4-membered ring diazene 3,4-diazatricyclo[4.2.1.0 2,5]non-3-ene (dtn) reacts with Cr and W carbonyls to give the complexes M(CO) 5(dtn))(Ia,b), [M(CO) 5] 2 (dtn) (IIa,b), M(CO) 4(dtn) 2 (IIIa,b), [M(CO) 4] 2(dtn) 2 (IVa,b), and [M(CO) 3] 2(dtn) 3 (Va,b) where a = Cr and b = W. 1H and 13C NMR provide evidence that compounds III-V each exist in the predicted two isomeric forms and full assignment of the resonances is made for all but the Va 13C spectrum. Fe 2(CO) 9 reacts with dtn to give Fe(CO) 4(dtn) (Ic) and Fe 3(CO) 9(dtn) (VIIIc). It is argued that steric effects from the hydrocarbon portion, notably C(9), of dtn prevents formation of the normally stable diiron complexes Fe 2(CO) 6(dtn) (VIc) and Fe 2(CO) 7(dtn) (VIIc). Ru 3(CO) 12 and dtn react to form only Ru 3CO) 9(dtn) (VIIId). Variable temperature 13C NMR studies reveal CO scramblingin VIIIc and VIIId at room temperature, which ceases at low temperature. Results for the dtn complexes are compared with results for another 4-membered ring diazene ligand as well as with results for 3−, 5−, and 6-membered ring diazenes.