Bipyridyl-metal complexes. 2. Synthesis and characterization of palladium(II) chloride complexes of 6-ferrocenyl-2,2'-bipyridine, 2-ferrocenyl-1,10-phenanthroline, and 6-ruthenocenyl-2,2'-bipyridine, and the single-crystal x-ray structure of (1,1'-bis(2,2'-bipyrid-6-yl)ferrocene-N,N')palladium chloride