Chiral C1- and C2-Symmetrical 2,2''-Bis(1-aminoethyl)-1,1''-biferrocenes: Synthesis, Structure, and Redox Chemistry

Unexpected 1,5-Dilithiation of Chiral o-TMS Blocked (Dimethylamino)phenylmethylferrocene: An Alternative Approach to Chiral Ferrocenyl 1,5-Diphosphanes

The 1,5-dilithiation of o-TMS blocked (dimethylamino)phenylmethylferrocene 4 unexpectedly occurred even though one equimolar amount of t-BuLi was used and the 1,5-dilithiated ferrocene 6 was trapped by iodine followed by removal of the TMS group to give the 1,5-diiodoferrocene 11 in a reasonable yield. The 1,5-diiodoferrocene 11 was converted into the diastereomer of Taniaphos 12 by sequential dilithiation and trapping with Ph2PCl. The rhodium and copper complex of 12 catalyzed well the asymmetric allylic alkylation with a Grignard reagent and hydrogenation with the alpha-acetamidocinnamic acid ester, respectively, with high enantioselectivities. The methoxy 1,5-diphosphane 14, of which the enantiomer is known as a good ligand for the rhodium-catalyzed asymmetric hydrogenation, was obtained by the inversive substitution of the dimethylamino group of 11 by NaOMe and subsequent dilithiation and trapping with Ph2PCl.

Electrocatalytical properties of polymethylferrocenyl dendrimers and their applications in biosensing

The electrochemical characterization of polymethylferrocenyl dendrimers deposited onto a platinum electrode and their applications as hydrogen peroxide and glucose sensor are described. The redox dendrimers consist of flexible poly(propileneimine) dendrimer cores functionalised with octamethylferrocenyl units. Amperometric biosensors for glucose were prepared by immobilization of glucose oxidase onto these modified electrodes. The influence of the dendrimer generation and the thickness of the dendrimer layer, the effect of the substrate concentration, and the interferences and reproducibility on the response of the sensors were investigated.

Ferrocenyl Compound as a Multiresponsive Calcium Chemosensor with Remarkable Fluorescence Properties in CH3CN

We have synthesized a novel disubstituted ferrocenyl compound [Fe(C5H4CO(CH=CH)2C6H4NEt2)2] (3) that displays a remarkable fluorescence quantum yield (1.1 x 10(-1)) in acetonitrile, and we have studied its capacity for calcium detection in depth using both electrochemical and optical techniques in this medium. The results of our NMR analysis reveal that the ligand-calcium interaction is CO-centered and that an uncommon equilibrium occurs between 3 and calcium triflate, involving five species of different stoichiometries. In contrast, our analysis of the UV-vis absorption data indicates that only three species of different stoichiometries are formed when calcium perchlorate is used with 3. Mass spectrometry measurements provide strong support for the formation of all these different species in solution. In addition, the electrochemical detection of calcium triflate by 3 leads to an irreversible Fe(II)/Fe(III) oxidation process with an unusual negative shift (-60 mV) caused by the (n)Bu4NBF4 salt effect on the Ca2+-3 interaction process. Compound 3 can also be an original optical probe to detect calcium perchlorate over a wide range of salt concentration by UV-vis absorption spectroscopy. The most original and intriguing property of compound 3 is that it exhibits an unprecedented "multistep" fluorescence behavior upon addition of this salt.

From Calcium Interaction to Calcium Electrochemical Detection by [(C5H5)Fe(C5H4COCHCHC6H4NEt2)] and Its Two Novel Structurally Characterized Derivatives

[(C(5)H(5))Fe(C(5)H(4)COCH=CHC(6)H(4)NEt(2))] (1) has been electrochemically evaluated toward different cations in solution. Calcium sensing by this compound and its two new derivatives [(C(5)H(5))Fe(C(5)H(4)CO(CH=CH)(2)C(6)H(4)NMe(2))] (2) and [(C(5)H(5))Fe(C(5)H(4)CH=CHCOCH=CHC(6)H(4)NEt(2))] (3) that exhibit a conjugated link between the ferrocene unit and the nitrogen atom has been thoroughly examined. Compounds 2 and 3 have been structurally characterized by single-crystal X-ray diffraction studies. The three related protonated species [1H][BF(4)] (4), [2H][BF(4)] (5), and [3H][BF(4)] (6) have been isolated in a good yield. NMR experiments clearly established that calcium interaction occurs in the vicinity of the carbonyl group, and mass spectrometry studies confirmed that this interaction, which involves several ligand-Ca(2+) adducts, is complex. A combination of electrochemical and NMR experiments highlighted an original salt influence on the electrochemical calcium sensing result.

Novel chiral biferrocene ligands for palladium-catalyzed allylic substitution reactions

Eleven novel aminophosphine ligands have been synthesized, all of which contain a chiral 2,2' '-bridged biferroceno unit as part of a biferrocenoazepine substructure. The efficiency of these compounds as chiral auxiliaries in palladium-mediated allylic substitution reactions has been investigated. Depending on the degree of (steric) fit between proper ligands and cyclic or noncyclic substrates, reactions with 46-87% ee were achieved. The molecular structure of a palladium dichloride complex of one of the ligands was determined by X-ray diffraction and compared to its binaphthyl analogue. In the solid state, the azepine substructure of these two complexes adopts totally different conformations with either local C(2) (binaphthyl) or local C(1) (biferrocene derivative) symmetry. These structural changes are well-reproduced by empirical force field calculations and are also reflected in significantly different behavior in asymmetric catalysis.

Synthesis of Chiral C(2)-Symmetric Bisferrocenyldiamines. X-ray Crystal Structure of Ru(2)Cl(2).2CHCl(3) (2 = N1,N2-Bis{(R)-1-[(S)-2-(diphenylphosphino)]ferrocenylethyl}- N1,N2-dimethyl-1,2-ethanediamine)

A new class of chiral C(2)-symmetrical bisferrocenyl diamines, N1,N2-bis[(R)-1-ferrocenylethyl]-N1,N2-dimethyl-1,2-ethanediamine (1) and N1,N2-bis{(R)-1-[(S)-2-(diphenylphosphino)]ferrocenylethyl}-N1,N2-dimethyl-1,2-ethanediamine (2), were prepared from the chiral template (R)-N,N-(dimethylamino)-1-ferrocenylethylamine ((R)-FA). Compound 1 was prepared from the reaction of (R)-FA with MeI followed by nucleophilic substitution with N,N'-dimethylethylenediamine, while 2 was formed from 1 via ortho lithiation followed by electrophilic substitution with chlorodiphenylphosphine. Compound 2 reacts with Ru(DMSO)(4)Cl(2) to give trans-Ru(2)Cl(2) (3) in which the ligand is tetradentate. This complex crystallizes in the orthorhombic system: P2(1)2(1)2(1) (No. 19); a = 11.7230(4) Å, b = 16.5951(6) Å, c = 27.853(1) Å; Z = 4; R = 0.046; R(w) = 0.104. The geometry around the central metal is an octahedron with a pair of chlorine atoms trans to each other. This complex exhibits catalytic activity toward asymmetric cyclopropanation of some olefins and alkyl diazoacetates, giving enantioselectivity up to 95%.

Reactivity of the Acyclic Diazadioxa Redox Active Ligand [(C(5)H(5))Fe(C(5)H(4)CH(2)N(CH(3))(CH(2))(2)OCH(2)-)](2): NMR, Electrochemical, and Mössbauer Studies. Crystal Structure of Its Copper Complex

Several novel diazadioxa ferrocenyl derivatives have been prepared along with their previously unknown electroactive precursor [(C(5)H(5))Fe(C(5)H(4)CH(2)N(CH(3))(CH(2))(2)OCH(2)-)](2) (2). Di-N,N'-protonated and -methylated species [2(H)(2)][X](2) (3a-c) (X = CF(3)SO(3), BF(4), PF(6)) and [2(Me)(2)][CF(3)SO(3)](2) (5), and N-H-N monoprotonated species [2H][X] (4a-c) have been isolated in high yield. The efficient syntheses of compounds [2Na][PF(6)] (6), [2Cu][CF(3)SO(3)] (7), [2Ag][CF(3)SO(3)] (8), and [2MCl(2)] (M = Zn, Hg) (9, 10) are reported. The crystal structure of complex 7 has been determined by X-ray analysis at 180 K. Crystal data: monoclinic P2(1)/c, with a = 11.511(2) Å, b = 19.613(2) Å, c = 14.493(2) Å, beta = 88.32(2) degrees, V = 3273.2(1) Å(3), Z = 4; R = 0.034, R(w) = 0.039 for 3379 observations and 407 variable parameters. The copper(I) atom, bound to the two O and two N atoms of the ferrocenyl ligand, is in a very distorted tetrahedral geometry with a large N(1)CuN(2) angle (163.1(2) degrees ). In cyclic voltammetry, 4a-c undergo two quasi-reversible (Fe(II)/Fe(III)) redox processes at 0.1 V s(-)(1). Electrochemical studies of 3a-c, 5, 7, and 8 show that diprotonation and dialkylation of 2 or complexation of a Cu (Ag) salt induces an anodic shift ranging from 240 to 110 mV. Chemical oxidation of 2 (5 equiv of Ag(I)) produces the cation [2(H)(2)](4+) (11). The quantitative two-step electrochemical oxidation of 2 at controlled potential in CH(3)CN also leads to 11: an ECE mechanism, in which the diprotonated species plays a key role, is proposed. Mössbauer data of 2, 3c, 6, 7, 8, and 11 are also presented.