Mono- and Dinuclear Five-coordinate Cyclometalated Palladium(II) Compounds

Reaction of cyclometalated halide-bridged Pd(II) complexes 1−4 with the tertiary triphosphine ligand (Ph2PCH2CH2)2PPh (triphos) yielded complexes [{(Ph2PCH2CH2)2PPh-P,P,P}Pd{N(Cy)=(H)C}C6H2{C(H)N(Cy)}Pd{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4]25, [Pd{C6H4-NNC6H5}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4] 6, and [Pd{R-C6H3C(H)NCy}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4] (7; R = 4-CHO, 8; 3-CHO). Spectroscopic and analytic
data suggest five-coordination on the palladium atom, which, for complexes 5, 6, and 7, was confirmed by X-ray
crystallography. The geometry around palladium may be view as a distorted trigonal bipyramid, with the palladium,
nitrogen, and terminal phosphorus atoms in the equatorial plane. Compound 5 is the first doubly cyclometalated
palladium(II) compound with two pentacoordinated metal centers. The structure of 6 comprises two discrete
cations with slightly different geometries, showing the importance of crystal packing forces in order to determine
the coordination arrangement.