The synthesis of tripodal nitrogen donor ligands and their characterization as Pd(II)Me2 and Pd(II)IMe derivatives

New tripod ligands containing pyridin-2-yl (py), N-methylimidazol-2-yl (mim), and pyrazol-l-y1 (pz) groups have been made by addition of 2-bromopyridine to deprotonated (py)(mim)CH2 or (mim)2CH2 to form (py)2(mim)CH and (py)(mim)2CH, or by simple condensation reactions of (pz)2CO with (mim)CHO or (py)CHO to form (pz)2(mim)CH and (pz)2(py)CH. The ligands may have general application in coordination and organometallic chemistry, especially bis(pyrazol-lyl)(pyridin-2-yl)methane [(pz)2(py)CH], which can be readily synthesized and is an unsymmetrical tripod closely related to (pz)3CH and (py)3CH. Dimethylpalladium( II) and methyl(iodo)palladium(II) complexes of the ligands have been isolated, and compared with complexes of (pz)3CH, (py)3CH, and (pz)4C.