Pd-2(0)(dba)(3) (dba = E,E-dibenzylidene acetone) is the most widely used Pd-0 source in Pd-mediated transformations. Pd-2(0)(dba-Z)(3) (Z = dba aryl substituents) complexes exhibit remarkable and differential catalytic performance in an eclectic array of cross-coupling reactions. The precise structure of these types of complexes has been confounding, since early studies in 1970s to the present day. In this study the soluiton and solid-state structures of Pd-2(0)(dba)(3) and Pd-2(0)(dba-Z)(3) have been determined. Isotopic labeling (H-2 and C-13) has allowed the solution structures of the freely exchanging major and minor isomers of Pd-2(0)(dba)(3) to be determined at high field (700 MHz). DFT calculations support the experimentally determined major and minor isomeric structures, which show that the major isomer of Pd-2(0)(dba)(3) possess bridging dba ligands found exclusively in a s-cis,s-trans conformation. For the minor isomer one of the dba ligands is found exclusively in a s-trans,s-trans conformaiton. Single crystal X-ray diffraction analysis of Pd-2(0)(dba)(3)center dot CHCl3 (high-quality data) shows taht all three dba ligands are found over two positions. NMR spectroscopic analysis of Pd-2(0)(dba-Z)(3) reveals taht the aryl substitutent has a profound effect on the rate of Pd-olefin exchange and the global stability of the complexes in solution. Complexes containing the aryl subtituents, 4-CF3, 4-F, 4-t-Bu, 4-hexoxy, 4-OMe, exhibit well-resolved H-1 NMR spectra at 298K, whereas those containing 3,5-OMe and 3,4,5-OMe exhibit broad spectra. The solid-state structures of three Pd-2(0)(dba-Z)(3) complexes (4-F, 4-OMe, 3,5-OMe) have been determined by single crystal X-ray diffraction methods, which have been compared with Goodson's X-ray structure Pd-2(0)(dba-4-OH)(3).