Metallacycles representation

The role of metallacycles, as intermediates in chromium-catalysed ethylene trim-erisation, is highlighted in this article. It is also shown that when 37 is treated with ethene in a protonolysis reaction, hexane and butane are liberated (1 3 ratio hexane butane). This observation gives strength to the argument that metallacycles are intermediates in chromium-catalysed ethylene trimerisation. Scheme 13 provides a simplified representation for chromium-based ethylene trimerisation. 

Fig. 13.15. Schematic representation of the most important orbital interactions in TM-aUcene and alkyne complexes and description as metallacyclic compounds (a) TM ligand o-donation (aj) and TM — ligand TT-backdonation ( 2) aUcene complexes, (b) Metallacyclopropane. (c) TMligand o-donation (a ), TM — ligand in-plane Try-backdonation ( 2) TM ligand out-of-plane ir -donation ( 1) and TM — ligand 8-backdonation (a2) in alkyne complexes, (d) Metallacycloropene. The symmetry assignments 2, 2...

Fig. 15 Schematic representation of the slipped-cofacial porphyrin metallacycle [trans,cis, cis-RuCl2(CO)2(3 -cisDPyP)]2 (10) and of the corresponding fnUy- and semi-zincated derivatives...

Figure 4.5 Transition structures of the metallacycle formation for the side- and bottom-bound pathways, and representation of the backdonation. Reproduced with permission from R Liu et al.,J. Am. Chem. Soc., 2012, 134,1464-1467. Copyright (2012) American Chemical Society. ...

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