Exposure of the isolable zirconocene sandwich compounds, (η5-C5Me5)(η5-C 9H5-1-R1-3-R2)Zr (R1 = Me, iPr, tBu; R2 = Me) to one atmosphere of dinitrogen resulted in N2 coordination. X-ray diffraction and NMR spectroscopy establish that the resulting dimeric dinitrogen compounds contain an unusual μ2,η2-bridging indenyl ring and a weakly activated N2 ligand. N2 coordination from the isolable zirconium sandwich compounds is extremely sensitive to the number and size of the indenyl subsituents. Compounds bearing two [iPr] or three methyl substituents are stable as η9 sandwich compounds for weeks under dinitrogen likely due to the inability to dimerize through a two-atom N 2 bridge. Performing the reduction of (η5-C 5Me5)(η5-C9H5-1- R1-3-R2)ZrCl2 (R1 = iPr, tBu; R2 = Me; R1 = R2 = SiMe 3) under an N2 atmosphere produced a different outcome; rare examples of side-on, end-on zirconium dinitrogen compounds were isolated and in one case, crystallographically characterized. Protonolysis studies with weak Brønsted acids were used to evaluate the relative activation of the bridging dinitrogen ligands.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry