Unusual 4-membered ring strained metalla-cycloallenes of the early transition metals Titanium, Zirconium and Hafnium

• Applicant: Professor Dr. Uwe Rosenthal
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2010 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 181753120

The result of this project should be unusual metallacycles of the early transition metals Titanium, Zirconium and Hafnium to find the limitations for the existence of such ring-strained systems for the example of unusual 4-membered metalla-cycloallenes. As such unusual 5-membered metallacycles exist metallacyclocumulenes (1-metallacyclopenta-2,3,4-trienes), metallacyclopentynes (1-metallacyclopenta-3-ynes) and metallacycloallenes (1-metallacyclopenta-2,3-dienes) odf the metals Ti, Zr and Hf,. whereas the smaller 4-rings like metallacycloallenes (1-metallacyclo-buta-2,3-dienes) are unknown for these metals. The synthesis of such compounds is interesting, because - like for the 5-membered metallacyclen - a general better knowledge of synthetical and theretical aspects for such organometallic compounds is expected which is relevant for catalytic C-C coupling reactions in the future. One can understand the compounds which were obtained during the last years are (as a result of other supported DFG-projects) better regarding the bonding situation because they were studied theoretically. The unexpected stability together with the chemical inertness was a part of the basic project and should be extended into two directions: - 5-membered hetero-metallacyclocumulenes and hetero-metallacycloalkynes - 4-membered all-C-metallacycles like metallacycloallenes (1-metallacyclo-buta-2,3-dienes) and corresponding 4-membered hetero-metallacycles Whereas in the basic project an extension to the hetero atoms such as N, P, O, S for such unusual ring systems was very well investigated by using hetero-butatrienes like R2C=C=C=X, X=C=C=X; X = O, S or R2C=C=C=XR, RX=C=C=XR; X = N, P, the new investigations of this project are concentrated to the synthesis of other 1-metalla-dihetero-cyclo-buta-2,3-dienes, of 1-metalla-monohetero-cyclo-buta-2,3-dienes and (by using the theoretical results of the basic project) and new synthetical methoids again to 1-metalla-all-C-cyclo-buta-2,3-dienes.

• DFG Programme: Research Grants