Bruno Longato

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.

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).

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

Variable coordination modes for 1,1′-bis(diphenylphosphino)ferrocene (dppf) mono- and di-chalcogenides or -oxides (dppfE and dppfE2; E = O, S or Se) in copper(I) complexes. Crystal structure of [{Cu(dppf)}2(μ-dppfS2)] (BF4)2 and [Cu(dppfSe)2]BF4

Abstract Reaction of [Cu(MeCN) 4 ]BF 4 with the phosphine Fe[ η 5 -C 5 H 4 PPh 2 ] 2 (dppf) and its disulfide (dppfS 2 ) sequentially in chlorinated solvents led to the dinuclear tricoordinate complex [{Cu(dppf- P , P ′)} 2 ( μ -dppfS 2 - S , S ′)] (BF 4 ) 2 ( 1 ), whereas reaction of the copper reagent with dppf and its diselenide (dppfSe 2 ) gave the bis-chelate dppf-monoselenide compound [Cu(dppfSe- P , Se ) 2 ]BF 4 ( 2 ). Similarly, the E = O or S relevant complexes [Cu(dppE- P , E ) 2 ]BF 4 were obtained by reaction of the copper(I) precursor with the dppf-monoderivatives [ η 5 -C 5 H 4 PPh 2 ]Fe[ η 5 -C 5 H 4 P(E)Ph 2 ] (dppfE). The complexes have been characterized by 1 H and 31 P NMR spectroscopy. Single-crystal X-ray structure determinations were performed for complexes 1 and 2 . Complex 1 crystallizes as CHCl 3 ( 1a ) or CHBr 3 ( 1b ) monosolvates. The cation of 1 is exactly centrosymmetric and shows a distorted trigonal planar coordination at copper with a PCuP angle of 115.7(1)° and the SCuP angles of 138.6(1) and 104.3(6)°, as mean values from 1a and 1b . In complex 2 the coordination geometry around the metal atom is markedly distorted tetrahedral with the two dppfSe moieties acting as chelating ligands with bite angles of 111.5(2) and 116.8(2)°. The Se(1)CuSe(2) angle (103.4(2)°) approaches the value for tetrahedral geometry, while the remaining angles differ significantly from the ideal value ranging from 96.1(2) to 121.9(3)°. The CuSeP angles (124.5(2) and 132.9(2)°) point towards a substantially sp 2 hybridization of the selenium atom.

Synthesis and molecular structure of cis-1-[(C6H5CH2)3PHC6H5)(CH2C6H5)2]-2-CH3-1,2-(σB10C2H10)

Abstract The title complex has been prepared from the reaction of cis-[(C6H5CH2)3P]2PtCl2 with 1-Li-2-Ch3-1,2-B10C2H10 and the crystal structure determined by X-ray single-crystal analysis. Crystals are triclinic, space group P 1 , with a 13.826(5), b 15.269(5), c 13.234(4) » and α 104.74(8), β 60.78(8), γ 107.46(8)°. The structure was solved by the heavy-atom method and refined to R 0.060 for 3855 independent reflections. The carboranyl group is σ-bonded to Pt through it C(1) atom. One phosphine is coordinated to the metal atom through its P atom, the other through its P atom and the C atom bonded to phosphorus of one benzyl side group, leading to a three-membrane P tPC chelate ring.

Heteropolymetallic complexes of 1, 1′-bis(diphenylphosphino)ferrocene, dppf IX. Electrochemical oxidation of the dicopper(I) complex cation [(μ-dppf)(Cu(dppf))2]2+. A multi-electron redox system

The electrochemical oxidation of the homoleptic dimeric complex [(μ-dppf)(Cu(dppf))2]2+ (dppf=1,1′-bis(diphenylphosphino)ferrocene) at a platinum electrode in 1,2-dichloroethane was studied by cyclic voltammetry and controlled potential electrolysis. The compound was found to undergo an apparently reversible single-stepped three-electron transfer process involving the three non-interacting ferrocene moieties. The electrogenerated pentacation was, however, unstable towards fragmentation into the fairly stable Cu(I)(dppf·+) complex, [Cu(dppf)]2+, and the fugitive bis(diphenylphosphino)ferrocenium radical cation, [dppf]·+, the ultimate fate of which was the formation of protonated and oxygenated dppf derivatives upon reaction with water present in the reaction medium. Subsequent back-reduction restored the starting dimer and produced the novel complex [Cu(dppf)(dppfO)]+, which was characterized by 31P NMR spectroscopy.

Synthesis, characterization and cytotoxic properties of platinum(II) complexes containing the nucleosides adenosine and cytidine

Cytidine (cyt) and adenosine (ado) react with cis-[L(2)Pt(μ-OH)](2)(NO(3))(2) (L=PMe(3), PPh(3)) in various solvents to give the nucleoside complexes cis-[L(2)Pt{cyt(-H),N(3)N(4)}](3)(NO(3))(3) (L=PMe(3), 1),cis-[L(2)Pt{cyt(-H),N(4)}(cyt,N(3))]NO(3) (L=PPh(3), 2), cis-[L(2)Pt{ado(-H),N(1)N(6)}](2)(NO(3))(2) (L=PMe(3), 3) and cis-[L(2)Pt{ado(-H),N(6)N(7)}]NO(3) (L=PPh(3), 4). When the condensation reaction is carried out in solution of nitriles (RCN, R=Me, Ph) the amidine derivatives cis-[(PPh(3))(2)PtNH=C(R){cyt(-2H)}]NO(3) (R=Me, 5a; R=Ph, 5b) and cis-[(PPh(3))(2)PtNH=C(R){ado(-2H)}]NO(3) (R=Me, 6a: R=Ph, 6b) are quantitatively formed. The coordination mode of these nucleosides, characterized in solution by multinuclear NMR spectroscopy and mass spectrometry, is similar to that previously observed for the nucleobases 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd). The cytotoxic properties of the new complexes, and those of the nucleobase analogs, cis-[(PPh(3))(2)PtNH=C(R){1-MeCy(-2H)}]NO(3) (R=Me, 7a: R=Ph, 7b), cis-[(PPh(3))(2)PtNH=C(R){9-MeAd(-2H)}]NO(3) (R=Me, 8a: R=Ph, 8b) have been investigated in a wide panel of human cancer cells. Interestingly, whereas the Pt(II) nucleoside complexes (1-4) did not show appreciable cytotoxicity, the corresponding amidine derivatives (7a, 7b, 8a, 8b, 5b, and 6b) exhibited a significant in vitro antitumor activity.

Role of the phosphine ligands on the stabilization of monoadducts of the model nucleobases 1-methylcytosine and 9-methylguanine in platinum(II) complexes

The addition of 1-methylcytosine (1-MeCy) or 9-methylguanine (9-MeGu) to solutions of cis-(PPh3)2P(ONO2)2 (1a), in a molar ratio of 1:1, affords the monoadducts cis-[(PPh3)2Pt(1-MeCy)(ONO2)]NO3 (2a) and cis-[(PPh3)2Pt(9-MeGu)(ONO2)]NO3 (3a) and only trace amounts of the bisadducts cis-[(PPh3)2Pt(1-MeCy)2](NO3)2 (4a) and cis-[(PPh3)2Pt(9-MeGu)2](NO3)2 (5a), respectively. The X-ray structural determination of 2a and 3a indicates a strong pi-pi stacking interaction between one of the PPh3 phenyl groups and the pyrimydinic N3-platinated cytosine or the imidazole part of the N7-coordinated guanine base. The addition of a further equiv of nucleobase to the monoadducts forms quantitatively the bisadducts that have been isolated as pure compounds 4a and 5a. Under the same experimental conditions, the dinitrato analogue cis-[(PMePh2)2Pt(ONO2)2] (1b) forms the monoadducts 2b and 3b in equilibrium with a relatively high concentration (20-30%) of the bisadducts cis-[(PMePh2)2Pt(1-MeCy)2](NO3)2 (4b) and cis-[(PMePh2)2Pt(9-MeGu)2](NO3)2 (5b), which have been structurally characterized by single-crystal X-ray analysis. The characterization of the isolated complexes by multinuclear NMR spectroscopy is also described.

Aluminium carboxylates in aqueous solutions. Part 2. Metal speciation in the AlIII–lactate–OH––H2O system

The tris(hydroxyl–carboxyl) chelated complex Al(lact)3(lact = lactate) dissolves in water to give stable acidic (pH ca. 3) solutions, in which free and metal-co-ordinated lactate ligands are detected by IR spectra in D2O. Proton NMR spectra (90 MHz) reveal that ligand exchange between metal-bonded and free lactate ligands occurs, also at +4 °C. The separate resonances due to metal-bonded and free lactate are clearly detected at 400 MHz. When the pH of an Al(lact)3 solution (analytical concentration 0.1 mol dm–3) is adjusted to 7.5 with NaOD the resulting 1H and 13C NMR spectra are very similar to those exhibited by a 0.3 mol dm–3 Na(lact) solution. The IR spectrum of the 0.1 mol dm–3 aluminium(III) solution displays two major bands at 1585 and 1420 cm–1 due to the unco-ordinated lactate ligands. A 0.1 mol dm–3 neutralised solution is (meta)stable for months and the whole of the data at pH 7.5 can be interpreted in terms of the release of most of the lactate from the co-ordination sphere of AlIII, with concomitant formation of metastable species including possibly [Al(OH)3(H2O)3].