Edison Stein

PREPARATION, CHARACTERIZATION AND ELECTROCHEMICAL STUDIES OF 1,1'-BIS( DIPHENYLPHOSPHINO)FERROCENE (DPPF) DERIVATIVES. CRYSTAL STRUCTURE OF DPPFCO(NO) 2 SBF6

Abstract The neutral dppfFe(NO)2 (1), the novel cationic [dppfCo(NO)2][SbF6] (2), as well as the dppfFe(CO)3 (3) dppf = 1,1′-bis-(diphenylphosphino)ferrocene) complexes were prepared and characterized. The interaction between the two metallic centers through the dppf ligand was studied in the solid state by 57Fe Mossbauer spectroscopy and in solution by cyclic voltammetry. The Mossbauer parameters are compared with those of other dppfMLn, complexes. Electrochemical studies performed on these complexes show the great influence of the MLn moiety on the redox processes of the dppf iron center. The crystal structure of complex 2 was determined (C34H28CoF6FeN2O2P2Sb). The compound crystallizes in the triclinic, space group P 1 , a = 10.441(2), b = 10.755(2), c = 17.320(5) A , α = 104.10(2), β = 0.504(10), γ = 111.504(10)°, U = 1744.7(7) A 3 , Z = 2, R = 0.0765, wR2 = 0.1878 . In this complex, the cobalt atom is coordinated to two nitrosyl ligands and to phosphorus atoms of the dppf ligand, providing a distorted tetrahedral geometry.

Reaction of [Fe3(CO)12] with bidentate phosphines: Redox behavior of products

Abstract The reactions of [Fe 3 (CO) 12 ] with the bidentate phosphines 1,2-bis(diphenylphosphino)ethane (dppe), 1,4-bis(diphenylphosphino)butane (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppf) and 1,4-bis(diphenylphosphino)benzene (dppbz) using trimethylamine N-oxide as decarbonylating agent produce the chelated [Fe 3 (CO) 8 ( μ -CO) 2 ( μ , η 2 -diphosphine)] and the new series of symmetrical [{Fe 3 (CO) 9 ( μ -CO) 2 } 2 ( μ , η 2 -diphosphine)] and unsymmetrical [Fe 3 (CO) 9 ( μ -CO) 2 ]( μ - η 2 -diphosphine)[Fe(CO) 4 ] bridged complexes, in reasonable yield. The complexes were characterized by IR, 31 P and 13 C NMR spectroscopy, and elemental analysis. Electrochemical studies on these compounds reveal that the substitution of one or more phosphine ligands for carbon monoxide of [Fe 3 (CO) 12 ] results in a more cathodic potential for the first reduction peak, but is insensitive to the σ-donor capabilities of the ligands.

Reaction of [Os3(CO)10(MeCN)2] with 2,3-bis(2-pyridyl)pyrazine and pyrazyne. Synthesis, characterization and electrochemical behavior of 1:1 and 1:2 ligand:cluster complexes

Abstract The diimine-bridged, bis-triosmium carbonyl complexes [{Os 3 (CO) 10 ( μ -H)} 2 (pyz)] 1b , [{Os 3 (CO) 10 } 2 (dpp)] 2b , (pyz=pyrazine; dpp=2,3-bis(2-pyridyl)pyrazine) and their corresponding 1:1 ligand:cluster complexes [Os 3 (CO) 10 ( μ -H)(pyz)], 1a , [Os 3 (CO) 10 (dpp)], 2a , were synthesized by the reaction of [Os 3 (CO) 10 (MeCN) 2 ] with pyz and dpp ligands. All compounds were characterized by IR, 1 H-NMR spectroscopy and elemental analysis. Electrochemistry was used to examine the redox properties of 1 – 2 and of complexes [Os 3 (CO) 10 ( μ -H)(py)], 3 , for comparison purposes. The electrochemical behavior of the bridged bis-triosmium species 1b – 2b provided strong evidence for the electronic interaction between the two metal centers.

Synthesis and electrochemical characterization of bimetallic ruthenium complexes with the bridging eta2( s,s )-1,3-butadiyne-1,4-diyl ligand

The bis(ruthenium)alkyne complex [cis-{RuCl (bpy)2(m-CoC-)}]2 (1) was obtained by treatment of 1 equiv of either 1,4-bis(trimethylsilyl)-1,3-butadiyne or bis(trimetylsilyl)acetylene with 2 equiv of cis-[RuCl2(bpy)2].2H2O, NaF and NaBF4 salts in methanol/CH2Cl2 mixture (10/1) in 52% and 35% yields, respectively. 1H, 13C{H} NMR and principally electrochemical analyses confirmed that the same product was obtained from the two reactions. Cyclic voltammetric analyses of (1) from 0 to 1.20 V displays two one-electron quasi-reversible oxidation peaks attributed to the Ru(II)/Ru(III) couple. The redox processes are separated by 520 mV, indicating a significant electronic communication between the two metallic centers.

(Sorbic acid)Fe(CO)2L complexes with L=CO, P(OPh)3, PPh3, and PEt3. Photolytic preparation, spectral properties, and bonding

Abstract The (sorbic acid)Fe(CO) 2 L complexes, with L = CO, P(OPh) 3 , PPh 3 and PEt 3 , have been prepared by irradiating the corresponding Fe(CO) 4 L compounds in benzene in the presence of sorbic acid. The Mossbauer spectra are compatible with the structure of a tetragonal pyramid with the iron(0) atom located in the center of the base. The values of the isomer shift, δ, seem to indicate that d π -L π ★ back bonding is predominant for L = CO, significant for L = P(OPh) 3 , and negligible for L = PPh 3 and PEt 3 . The order of decrease of the frequencies ν(CO) of the coordinated sorbic acid parallels the order of increase of the σ-donor ability of L.

Effects of the ligands on the electrochemical oxidation of (benzylydeneacetone)Fe(CO)2L, with L = CO, phosphines and phosphites

Abstract Half-peak oxidation potentials, E p/2 ox were obtained for two congeneric series of (BDA)Fe(CO) 2 L (BDA=(C 6 H 5 )CHCHC(O)CH 3 , benzylideneacetone) complexes, one with L=CO, phosphites and the other with L=phosphites. Correlations of the E p/2 ox data with ligand parameters such as Giering electronic parameter, χ d , for the phosphorus ligands, and Mossbauer isomer shifts, − δ , and quadrupole splittings, Δ E q , for the iron atom are presented. These correlations helped to describe and quantify the electronic effects of the phosphorous ligands on the Lewis acid iron(0) center. Transmission of these effects to the BDA ligand throughout the metal center was also examined. The results support the idea that d π L π* back bonding is predominant for L=CO, significant for L=phosphites, and small for L=phosphines.

Mössbauer spectroscopy of (benzylideneacetone)Fe(CO)2L complexes with L=Co, phosphites and phosphines. An analysis of ligand effects

Abstract The (benzylideneacetone)Fe(CO) 2 L complexes, with L = CO, PPh 3 , PMePh 2 , PMe 2 Ph, PEt 3 , PCy 3 , P(OPh) 3 , P(OMe) 3 , P(OEt) 3 and P(O i Pr) 3 have been studied by Mossbauer spectroscopy. The spectra are compatible with a distorted octahedral geometry with the iron atom at the center. The isomer shifts δ and quadrupole splittings Δ E q are correlated with the Giering electronic parameter χ d of the phosphines and phosphites and with the 13 C NMR complex shifts ΔC 4 of coordinated benzylideneacetone. The results are discussed in terms of the stereoelectronic effects of the ligand L. Correlation between isomer shifts and quadrupole splittings indicates that dπ-Lπ★ back bonding is predominant in the complexes with L = CO and phosphites and negligible in the complexes with L = phosphines.

Electronic interactions in [Ru3(mu3-R² CCC6H4-4-R¹)(mu -dppm)(mu-CO) (CO)7] (R¹ = NO2 and R² = Fc; R¹ = NO2, CN and R² = Ph)

The co-ordination of FcCCC6H4-4-NO2 (1) to a ruthenium carbonyl cluster to yield [Ru3(m 3-FcCCC6H4-4-NO2) (m-dppm)( m-CO)(CO)7] (2) is reported. The cyclic voltammograms of these compounds and of the analogous clusters [Ru3(m3 -h2-C6 H5CCC6H4-4-R)(m -dppm)(m -CO)(CO)7] (R= H, 3; CN, 4; NO2, 5) allowed an evaluation of the electronic communications between the different redox sites (ferrocenyl and -NO2 groups, and Ru3 moiety) and an analysis of the relative electron donor-acceptor capabilities of each of the three redox centres that compose 2. Furthermore, the inertness of 2, compared with clusters 3-5 which loose CO readily was attributed to the interaction between the ferrocenyl group and the metallic frame.