title: Comparisons between yttrium and titanium N-heterocyclic carbene complexes in the search for early transition metal NHC backbonding interactions.
abstract: The d (0) yttrium N-heterocyclic carbene compound YL 3 (L = OCMe 2CH 2[C{N(CHCH)NPr ( i )}]) has been made and structurally characterized. It adopts a mer configuration of the three bidentate ligands. A comparison of this with the isostructural d (1) titanium complex TiL 3 is made in order to seek experimental evidence of a pi-bonding contribution to the M-C bond. This has been augmented by DFT calculations. Experimentally, the metal radius-corrected Ti-C distance is shorter than the Y-C distance, suggesting a pi-bonding contribution in the d (1) complex, but the computational data suggest that a shorter sigma bond might simply be formed by the more strongly polarizing titanium cation. From the potassium reduction of TiL(OPr ( i )) 3, only a byproduct arising from silicone grease activation was isolable, identified as a mixed-valent, multinuclear, d (0)/d (1) cluster [Ti (III)L 2{Pr ( i )OSiMe 2O}K 2OTi (IV)(OPr ( i )) 4] 2 in which the carbene ligands are bound to the Ti (III) centers in preference to Ti (IV), with longer Ti-C distances than those found in TiL 3.
authors.affiliation: School of Chemistry, Joseph Black Building, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, United Kingdom. Polly.Arnold@ed.ac.uk
authors.forename: Polly L
authors.initials: PL
authors.lastname: Arnold
authors.forename: Sergey
authors.initials: S
authors.lastname: Zlatogorsky
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Jones
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Carmichael
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Liddle
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Blake
authors.forename: Claire
authors.initials: C
authors.lastname: Wilson