The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes

摘要

Across the periodic table the trans -influence operates, whereby tightly bonded ligands selectively lengthen mutually trans metal–ligand bonds. Conversely, in high oxidation state actinide complexes the inverse- trans -influence operates, where normally cis strongly donating ligands instead reside trans and actually reinforce each other. However, because the inverse- trans -influence is restricted to high-valent actinyls and a few uranium(V/VI) complexes, it has had limited scope in an area with few unifying rules. Here we report tetravalent cerium, uranium and thorium bis (carbene) complexes with trans C=M=C cores where experimental and theoretical data suggest the presence of an inverse- trans -influence. Studies of hypothetical praseodymium(IV) and terbium(IV) analogues suggest the inverse- trans -influence may extend to these ions but it also diminishes significantly as the 4 f orbitals are populated. This work suggests that the inverse- trans -influence may occur beyond high oxidation state 5 f metals and hence could encompass mid-range oxidation state actinides and lanthanides. Thus, the inverse- trans -influence might be a more general f -block principle.