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A variety of mono- and bisphosphine sulfides and selenides were synthesized and structurally characterized by NMR spectroscopy. In addition, the X-ray crystal structures were determined for eleven of these compounds. The percent buried volume was determined from the X-ray structures and the use of this measurement in estimating the steric bulk in phosphine sulfides and selenides was further developed. The oxidation of the mono- and bisphosphine chalcogenides was examined using cyclic voltammetry in methylene chloride and acetonitrile. The solvent had little effect on the observed trends in the potentials at which oxidation occurred. Both the mono- and bisphosphine chalcogenides display an irreversible oxidative wave. Many of the phosphine selenides also display a follow-up, irreversible reductive wave indicative of the formation of a Se–Se bond upon oxidation. However, the products for the oxidation of the phosphine selenides could not be isolated by chemical oxidation. The potential at which oxidation of the phosphine sulfides occurs is more positive than the analogous phosphine selenides. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemistry of 1,1′-bis(diphenylphosphino)cobaltocenium hexafluorophosphate ([dppc][PF6]), 1,1′-bis(dicyclohexylphosphino)cobaltocenium hexafluorophosphate ([dcpc][PF6]), 1,1′-bis(di-iso-propylphosphino)cobaltocenium hexafluorophosphate ([dippc][PF6]), and 1-(di-tert-butylphosphino)cobaltocenium hexafluorophosphate ([1-dtbpc][PF6]) was examined in methylene chloride with tetrabutylammonium hexafluorophosphate as the supporting electrolyte. A reversible reductive wave followed by an irreversible wave at more negative potentials was observed. Ten new phosphinothioyl ([dppcS2][PF6], [dcpcS2][PF6], [dippcS2][PF6], [1-dtbpcS][PF6], and 1,1′-bis(dicyclohexylphosphinothioyl)ferrocene) and phosphinoselenoyl derivatives ([dppcSe2][PF6], [dcpcSe2][PF6], [dippcSe2][PF6], [1-dtbpcSe][PF6], and 1,1′-bis(dicyclohexylphosphinoselenoyl)ferrocene) were prepared and characterized, and the structures of eight of these compounds were determined. The electrochemistry of these phosphinochalcogenyl cobaltocenium compounds, as well as the previously prepared [dppcO2][PF6], displayed two reversible reductive waves at potentials less negative than that of the free phosphines. A correlation was found to exist between the Hammett substituent constant σ p and the reduction potentials of these compounds. In addition, the phosphinoselenoyl [dppcSe2][PF6], [dcpcSe2][PF6], and [dippcSe2][PF6] displayed an electrochemically irreversible oxidative wave, potentially indicating an intramolecular Se–Se bonded trication. The electrochemistry of three new and five previously reported transition metal complexes of the general formula [MnCl2(P∩P)][PF6] (M = Pd or Pt, n = 1, P∩P = dppc, dcpc or dippc; M = Au, n = 2, P∩P = dppc or dcpc)) was also examined displaying at least two reductive waves at potentials less negative than that of the free phosphines. Comparison of the electrochemical data with that previously obtained for analogous ferrocenes indicates that a correlation exists between the reduction potentials of the cobaltocenium phosphines and the potentials at which oxidation of the ferrocene phosphines occurs. In addition, the structure of [Au2Cl2(dppc)][PF6] was determined. [Copyright &y& Elsevier]

The reaction of [Pd(dtbpf)Cl2] (dtbpf = 1,1′-bis(di-tert-butylphosphino)ferrocene)with a chemical oxidant ledunexpectedly to the formation of [Pd(dtbpf)Cl]+. Furtherstudy found that a variety of reagents could be used to abstract achloride ligand from [Pd(dtbpf)Cl2] to yield [Pd(dtbpf)Cl]+. The solid-state structure suggests the formation of an Fe–Pdinteraction. The presence of the bulky tert-butylgroups is essential, as similar reactions with [Pd(PP)Cl2] (PP = other 1,1′-bis(phosphino)ferrocene ligands) resultsin the formation of [Pd(PP)(μ-Cl)]22+.The analogous platinum compounds have also been investigated and appearto behave in a similar manner. Similar compounds of the type [M′(PP)(PR3)]2+(M′ = Pd, Pt, R = Ph, Me) have beenprepared, and a metal–metal interaction has also been observed.Steric and electronic effects dictate the formation of these compounds.X-ray crystal structures were obtained for eight of these compoundsand were used as the basis for a computational analysis of the metal–metalinteraction. DFT analysis indicates the presence of a weak, noncovalentinteraction between the two metal centers. The electrochemical propertiesof these compounds were examined by cyclic voltammetry and typicallyshow one oxidative wave and either one two-electron or two one-electronreductive waves. [ABSTRACT FROM AUTHOR]