Solid state structure, magnetic susceptibility, and single crystal ESR properties of cis-diammineplatinum .alpha.-pyridone blue

Temperature Dependent ESR Studies on Platinum Pyrimidine “Blues”: Evidence for a Structural Instability ?

“…1, 2. This type of spectrum, termed "type 0" [10], has been obtained previously, in a similar form, for a number of Pt "blues" compounds [3,7,11].…”

“…The same holds true for their detailed molecular structure, as structure analysis is severely impeded by the fact that the compounds have never been obtained in the crystalline form. It is generally assumed, however, that the "blues" form oligomeric compounds as a result of partial oxidation and axial stacking of planar Pt monomers [2][3][4][5][6][7][8][9][10][11][12]. This assumption is consistent with X-ray diffraction studies of a crystalline PDDa-a-pyridone system [6].…”

“…In terms of an idealized model it appears plausible to envisage those oligomers as a discordered ID system. The discorder, as described by a random potential VR, may arise from variations of the local ligand-to-Pt stoichiometries and from distortions of the ideal ID geometry found for instance in the case of PDDa-apyrimidine from X-ray analysis [6,7]. These effects can be expected to be especially pronounced after short reaction times.…”

“…The Pt pyrimidine "blues" exhibit paramagnetism [3,[7][8][9][10][11]13] which can be detected by means of electron spin resonance (ESR) spectroscopy. The ESR results are consistent with the assumption that the unpaired electron spin is located in the 5d2 2 -orbital.…”

Crystal and molecular structure and 31P and 195Pt nmr spectroscopy of [Pt3S2(PMe2Ph)6][BEt4]2; a trinuclear complex containing triply-bridging sulphide ligands

“…In cluster complexes containing Pt3 triangles, distances in the range 2.6-2.8 are generally found (22,23). In a-pyridone blue (24), and in related complexes containing two Pt !toms bridged by pyrimidine bases (25), values up to 2.98 A have been considered short enough to suggest metal-metal bonding. A correlation between partial oxidation states and the resonating valence bond theory of metals ha: shown that some weak interactions may persist to about 3.2 A (26), and SCF-Xa-SW calculations on [Rh,Cl2(CO),] have suggested a metal-metal interaction as the explanation for the "bent" structure (27).…”