Electron-deficient η1-Indenyl,η3-allylpalladium(II) complexes stabilized by fluxional non-covalent interactions

Highly fluxional, solution-persistent, and formally electron-deficient (32e(-)) binuclear Pd(II)-C(0) complexes of 2-methyl-1H-indene were synthesized and structurally characterized by X-ray diffraction analysis. DFT investigations combined with a number of theoretical analyses of the bond framework suggest that the polar intermetallic interaction possesses no major covalent character. Instead of bearing a static metal-metal bond as suggested by structural X-ray diffraction analysis, the complexes display in solution significant fluxionality through haptotropy, i.e., a formal "oscillation" of the Pd(η(3)-allyl) moiety between two limiting η(1)-indenyl configurations.

The organometallic chemistry of cycloheptatrienyl zirconium complexes

This tutorial review summarizes the organometallic chemistry derived from the half-sandwich complex [(η(7)-C(7)H(7))ZrCl(tmeda)], which was used as an efficient and versatile starting material for the incorporation of monoanionic ligands into the cycloheptatrienyl zirconium coordination sphere by conventional salt metathesis reactions. A broad variety of ligands was employed, affording novel and previously inaccessible cycloheptatrienyl (sandwich) complexes of the type [(η(7)-C(7)H(7))Zr(Y)]; Y comprises pentadienyl, cyclopentadienyl, allyl, phospholyl, boratabenzene, imidazolin-2-iminato and amido systems. The cycloheptatrienyl ring in these systems usually acts as an "innocent spectator ligand", but reactivity can arise from the second ligand Y or the Lewis acidity of the, formally, Zr(+iv) center, which was probed in selected examples and put in perspective to related studies. The corresponding results emphasize why the use of [(η(7)-C(7)H(7))ZrCl(tmeda)] is clearly an advancement in the chemistry of the still fairly unexplored area of cycloheptatrienyl transition metal complexes.