Giuseppe Pilloni

Heteropolymetallic complexes of 1,1′-Bis(diphenylphosphino)ferrocene (dppf). III. Comparative physicochemical properties of (dppf)MCl2 (M = Co, Ni, Pd, Pt, Zn, Cd, Hg)

Abstract 1,1′-Bis(diphenylphosphino)ferrocene (dppf) metal dichlorides (metal = Co, Ni, Pd, Pt, Zn, Cd, and Hg) are examined as a class of related complexes. Their electronic, infrared, mass, 31P NMR, and Mossbauer spectra as well as the HeI and HeII photoelectron spectra of dppf are presented and discussed. Cyclovoltammetric tests in dichloroethane indicate that the ferrocene moiety undergoes a strong stabilization towards oxidation, and the ferricinium derivatives are well characterized in the case of Pd(II) and Pt(II). Differential scanning calorimetric tests reveal that all the complexes are thermally very stable, particularly the Zn(II) and Cd(II) derivatives, which melt without previous decomposition in the temperature range 300–305 °C. Cyclovoltammetric and field desorption mass spectral tests reveal that the [(dppf)MCl2]+ species are stable only when M = Pd, Pt.

Heteropolymetallic complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf): VII. Redox behaviour of dppf

Abstract The electrochemical oxidation of 1,1′-bis(diphenylphosphino)ferrocene (dppf) at a platinum electrode in 1,2-dichloroethane has been studied by cyclic voltammetry, controlled potential electrolysis, and 31P NMR spectroscopy. The compound undergoes a ferrocene-based reversible oxidation, which is followed by a fast chemical reaction, involving the phosphorus substituent on the cyclopentadienyl rings, to give dppfO, dppfO2, dppfH+ and dppfH22+. Kinetic data suggest that the reaction involes a reversible intramolecular electron transfer between the ferrocene core and the electron-rich substituents to give a phosphinium radical ion, which undergoes a second order rate-determining dimerization or a reaction with the parent compound to give a ferrocenylphosphine dimer cation radical, the ultimate fate of which is the formation of protonated and oxygenated dppf derivatives by nucleophilic attack by water present in the reaction medium. Evidence for the formation of the transient monomeric phosphinium radical was obtained by trapping it with 1,1′-diphenylethylene to give phosphorus-bonded monoalkene adducts of dppf.

Heteropolymetallic complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf). IV. Solvolytic behavior and cytostatic properties towards the KB cell-line of dppf and 1,2-bis(diphenylphosphino)ethane cis-complexes of Pt(II) and Pd(II)

Abstract The novel cis-platinum(II) complexes [(dppe)Pt(μ-OH)]2(BF4)2 and [(dppe)Pt(DMF)2](BF4)2 have been prepared and characterized by 31P NMR, together with cis-[(dppe)Pt(μ-Cl)]2(BF4)2, both in poorly and strongly coordinating solvents (dppe = 1,2-bis(diphenylphosphino)ethane). All these complexes and their dppf analogs (dppf = 1,1′-bis(diphenylphosphino)ferrocene) as well as (dppf)PtCl2, (dppe)PtCl2, (dppf)PdCl2, [(dppf)Pd(μ-Cl)]2(BF4)2 and [(dppf)Pd(μ-OH)]2(BF4)2 have been tested as antiproliferating agents towards Eagles KB cell-line. Their activity is compared with that of free diphosphine ligands. For Pt(II) complexes, the ID50 figures are found to be higher than those observed for free dppf and dppe. On the contrary, the activity of the palladium dppf complexes is substantially identical to that of free diphosphine.

Electrochemistry of coordination compounds. V. Electrochemical reduction of Ni(II), Pd(II), Pt(II) complexes with 1,2-bisdiphenylphosphinoethane: A comparison between polarographic data and nucleophilic substitution reactions on d8 square planar metal complexes

Abstract The electrochemical reduction of d 8 ionic complexes of nickel, palladium and platinum with 1,2-bisdiphenylphosphinoethane is presented. The obtained thermodynamic data suggest the relevance of the electron uptake ability in the determining the kinetic behaviour in S N 2 reactions on complexes with same configuration. The well known difference between lighter and heavier elements of the same group is once again observed: nickel(II) is reduced in two one-electron steps involving a rare Ni(I) complex while platinum(II), palladium(II) take up two electrons in a single process.

Electrochemistry of coordination compounds XV. Paramagnetic hydrido complexes of cobalt(II), rhodium(II) and iridium(II)☆

Abstract The electrochemical behaviour of a series of d8-hydrido complexes of cobalt, rhodium and iridium containing phosphorus ligands has been studied. The oxidation proceeds in two one-electron steps involving a rare hydrido complex in the II state, which, in the case of rhodium and iridium, is unstable and decays through a disproportionation pathway. An oxidationreduction mechanism accounting for the chemical and electrochemical results is proposed.

Dalton communications. Synthesis and structure of the first phosphine oxide complex of copper(I): evidence for a marked ‘borderline’ character of the metal centre

The remarkable stability of [Cu(dppf)(odppf)]BF4[dppf = 1,1′-bis(diphenylphosphino)ferrocene, odppf = 1,1′-bis(oxodiphenylphosphoranyl)ferrocene], characterized in the solid state by X-ray analysis and in solution by 31P NMR spectroscopy, reveals a marked borderline character of copper(I).

Electrochemistry of coordination compounds: II. Electrochemical reduction of di-(1,2-bisdiphenylphos-phinoethane)M(I) chloride: A new route to hydrido di-(1,2-bisdiphenylphosphinoethane)M(I) (M=Rh, Ir)

Summary The electrochemical behaviour of di-(1,2-bisdiphenyl-phosphinoethane)M(I) chloride (M=Rh, Ir) has been investigated on the mercury electrode in acetonitrile. The reduction proceeds in both cases via a two-electron step leading to anionic complexes which react in the applied solvent forming the corresponding hydrides. This behaviour suggests a new route to hydrido complexes. A comparison is made with the chemical behaviour of the anionic d 10 M(−I) complexes previously reported and a tentative interpretation is proposed.

The cleavage by iodine of the tin-tin bond in R6Sn2 compounds. Kinetics and mechanism

Abstract The rates of cleavage of selected ditin compounds by iodine have been measured in alcoholic solvents. Possible mechanisms for the cleavage are discussed. It is concluded that an acyclic four-center intermediate, formed after attachment of solvent in a fast preliminary step, provides the best explanation of the experimental results.

Electrochemistry of coordination compounds: XIII. Ruthenium(I) and ruthenium(0) complexes generated by electrochemical reduction of chlorodi-(1,3-bisdiphenylphosphinopropane)ruthenium(II)-hexafluorophosphate

Abstract The electrochemical reduction of chlorodi-(1,3-bisdiphenylphosphinopropane)ruthenium(II)hexafluorophosphate, [RuCl(DPP)2](PF6), has been studied on the mercury electrode in 1,2-dimethoxyethane +0.1 M TBAP. The polarogram shows two reversible one-electron waves corresponding to the formation of [RuCl(DPP)2] and [RuCl(DPP)2]. Both products are unstable and decay through a disproportionation pathway and a fast internal metalation via Cl− elimination with formation of HRu(C6H4PPh·CH2CH2 CH2·PPh2)(DPP), respectively. The hypothesis is put forward that the geometry of a metal-complex can be one of the factors which allow us to obtain d7 monomeric complexes by electrochemical methods.

Heteropolymetallic complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf): VI. Synthesis and crystal structure of [Rh(dppf)(η6-C6H5B(C6H5)3]☆

Abstract The complex [Rh(COD)(dppf)]ClO 4 (COD = 1,5-cyclooctadiene; dppf = Fe((η 5 -C 5 H 4 )P(C 6 H 5 ) 2 ) 2 ) has been prepared by removal of the chloride ligand from [RhCl(COD)] 2 by AgClO 4 in acetone, followed by addition of one equivalent of 1,1′-bis(diphenylphosphino)ferrocene. Reaction of [Rh(COD)(dppf)]ClO 4 with dihydrogen in the presence of NaBPh 4 affords the neutral complex [Rh(dppf)(η 6 -C 6 H 5 )B(C 6 H 5 ) 3 ], which has been characterized by single crystal X-ray analysis. The Rh(dppf) + ion interacts strongly with the tetraphenylborate anion, one of the C 6 C 5 groups being η 6 -coordinated to the metal. The plane defined by the two P atoms of the chelated bisphosphine and the Rh atom is almost perpendicular to the mean plane containing the η 6 -bonded phenyl group. The 1 H and 31 P NMR spectra of the isolated complexes are also discussed