Adducts of C02, CS2, CO, aldehydes, ketones, acetone oxime, and thiourea with peroxobis(triphenylphosphine)platinum(II) and analogs (or the corresponding tetrakisphosphineplatinum(O) complex in the presence of oxygen) have been prepared. Most of the adducts are thought to have a five-membered ring structure involving a peroxo group, and the reactions of these adducts, particularly with reducing agents, have been studied. It has been shown that in many cases, the five-membered peroxo-containing ring can be reduced to a fouror three-membered ring without a peroxo group. The original adducts are characterized by the disappearance of the unsaturated infrared stretching frequency [y(C=0), v(C=S), or y(C=N)], and for most of the compounds, the infrared vibrations
The solubilities of cesium metaperiodate in aqueous solutions of pH 1.3-5.8 have been measured a t 5.0, 25.0, and 40.0". The values calculated for K,,O a t these temperatures were (3.96 =IC 0.17) X(2.24 4 0.07) X 10-3, and (6.53 & 0.04) X 10-3. Evidence was found for a new periodate phase in the system H~O-CSIOC-CSOH, and two previously unreported cesium periodate salts were prepared.The equilibrium constant Kdo and thermodynamic quantities for the reaction HaIOs-(aq) e IO4-(aq) + 2H20(1) have been determined in the temperature range 2-18" by means of a nuclear magnetic resonance technique. The extrapolated value of KdO a t 25' was found to be 29. The corresponding vnltte of AG,!" wts -2 . 0 2~ 0.1 kcal/mole, of AHd" was 14.8 + 1.1 kcal/mole, and of 4.S,io was 50 f 4 eu.At2S0, AGsolno = 1.91 =! = 0.05 kcal/mole, AHSoino = 13.1 kcal/mole, and ASsolno = 37.6 eu.
Conclusions. This study has produced several molecular palladium(II) complexes that contain both Nand S-bonded thiocyanate ions. With the ligands PAs, PC2N, and PC3N, it is impossible to ascertain definitively whether the mixed mode of thiocyanate coordination is due to steric hindrance or to the trans electronic influences of the donor atom, since the predicted results are the same, and in agreement with the observations. With the ligands PP, SP, FSP, and SeP, steric considerations alone favor two S-bonded thiocyanate ions. Isolation of the stable, mixed complex [Pd(C26H24P2)-(SCN)(NCS)] and the reversible isomerization of [Pd-(C26H24As2)(SCN)2] in solution illustrate the delicate balance of electronic, steric, and solvent forces that influence the nature of thiocyanate coordination in a given complex.Acknowledgments. The authors are grateful to Professor John Burmeister for several helpful suggestions on the original version of this paper, and to Professor G. J. Palenik for determining the structures of [Pd(PP)-(NCS)(SCN)] and [Pd(PC3N)(SCNXNCS)] by X-ray three-dimensional crystallography.
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