Reactions of 1,4- and 2,3-Diazadienes with Titanocene and Zirconocene Complexes of Bis(trimethylsilyl)acetylene: Acetylene Coupling or Substitution Including Subsequent C−H Activation, C−C Coupling, and N−N Cleavage to Heterobimetallic Complexes

The reaction of 1,4-diazadienes RNCHCHNR with the titanocene and zirconocene complexes of bis(trimethylsilyl)acetylene Cp2M(L)(η2-Me3SiC2SiMe3) (M = Ti, without L (1); M = Zr, L = THF (2), pyridine (3)) is a general and new method to obtain 1-metalla-2,5-diazacyclopent-3-ene complexes Cp2M(η2-1:4-RNCHCHNR) (M = Zr, R = 2,6-iPr2C6H3 (4a), 4-Me-C6H4 (4b), Cy (4c); M = Ti, R = 2,6-iPr2C6H3 (5a), 4-Me-C6H4 (5b), Cy (5c)). In the analogous reaction with differently substituted azines RR‘CNNCRR‘ the products depend strongly on the metals used, Zr and Ti, as well as on the substituents R and R‘. With R = R‘ = Me and M = Ti, a substitution of the alkyne by the azine and a subsequent CH activation to the 1-titana-2,3-diazacyclopent-3-ene species 6 was observed. Using R = Ph and R‘ = H the acetylene was also substituted and, by a reductive coupling of two azine molecules, the paramagnetic binuclear Ti(III) complex (Cp2Ti)2[μ-(η4-2:3,6:7-PhHCNNCHPhCHPhNNCHPh) (7) was formed. With M = Zr and R = Ph and R‘ = H no subs...