Pyrazolato-Bridged Polynuclear Palladium and Platinum Complexes. Synthesis, Structure, and Reactivity

Cyclic trinuclear complexes [Pd3(μ-pz)6] (1) and [Pd3(μ-4-Mepz)6] (2) and dinuclear complex [Pd2(μ-3-t-Bupz)2(3-t-Bupz)2(3-t-BupzH)2] (3) have been prepared by the reactions of [PdCl2(CH3CN)2] with pyrazole (pzH), 4-methylpyrazole (4-MepzH), and 3-tert-butylpyrazole (3-t-BupzH), respectively, in CH3CN in the presence of Et3N. In the absence of the base, treatment of [PdCl2(CH3CN)2] with pzH gave the mononuclear complex, [Pd(pzH)4]Cl2 (6). The reaction of [PtCl2(C2H5CN)2] with pzH in the presence of Et3N under refluxing in C2H5CN afforded the known dimeric Pt(II) complex, [Pt(pz)2(pzH)2]2 (7). The protons participating in the hydrogen bonding in 3 and 7 are easily replaced by silver ions to give the heterotetranuclear complex [Pd2Ag2(μ-3-t-Bupz)6] (4) and the heterohexanuclear complex [Pt2Ag4(μ-pz)8] (5). The complexes 1−6 are structurally characterized.