Coordination of neutral, methylene bridged bis-guanidyls at palladium

The bis-guanidyl compound H2C{hpp}2 (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]- pyrimidine) coordinates to palladium(II) as a neutral, chelating N,N-bidentate ligand. Structural analysis of PdMeCl(H2C{hpp}2) shows a non-planar metallacycle that is twisted relative to the square plane of the metal and an anagostic interaction with a CH from the bridging methylene group. Generation of the cationic palladium complex, [PdCl(H2C{hpp}2)][OTf] was achieved by halide abstraction from the dichloride PdCl2(H2C{hpp}2) using NaOTf. The product was identified as a mixture of different species in solution; in the solid-state, the molecular structure is dimeric, consisting of the m,m-dichlorobridged dication. The new bis-guanidyl compound H2C{tbo}2 (Htbo = 1,4,6-triaza-bicyclo[3.3.0]oct-4-ene) was synthesized, and structurally characterized. Coordination of this compound at palladium dichloride was accompanied by ionization of the PdCl bond, and formation of the dication [Pd(H2C{tbo}2)2][Cl]2. Structural analysis shows a significant reduction in the twisting of this ligand