Comparing Interactions of a Three-Coordinate Pd Cation with Common Weakly Coordinating Anions

A series of complexes
Pd­(IPr)­(C­(O)­C9H6N)­X
has been prepared where X is a weakly coordinating anion (WCA). [Pd­(IPr)­(C­(O)­C9H6N)]+ can be isolated as a 3-coordinate,
air- and moisture-stable Pd­(II) cation when paired with sterically
encumbered WCAs. Using NMR, IR, X-ray diffraction, and computational
(DFT, NBO) techniques, the coordination ability of WCAs in both solid
and solution state is compared. The IPr methine isopropyl 1H NMR chemical shift and the anion’s percent buried volume
(%Vbur) are highly sensitive to the steric
encumbrance of the anion, while IR and NBO analysis offer a measure
of relative donor strength. On the basis of computed νCO, the coordinating abilities of anions studied are as follows BArF4– ∼ [(BCF)2(imid)]− < SbF6– < PF6– < BF4– < NTf2– < ClO4– < OTf– < Cl–.