Françoise Dahan

Nature of the Magnetic Interaction in the (Cu2+, Ln3+) Pairs: An Empirical Approach Based on the Comparison Between Homologous (Cu2+, Ln3+) and (NiLS2+, Ln3+) Complexes

The magnetic interaction in a series of isomorphous Cu2+–Ln3+complexes (1) is antiferromagnetic for LnCe, Nd, Sm, Tm, Yb and ferromagnetic for Ln=Gd, Tb, Dy, Ho, Er, while no interaction is operative for Ln=La, Pr, Eu, Lu.

Unprecedented Ferromagnetic Interaction in Homobinuclear Erbium and Gadolinium Complexes: Structural and Magnetic Studies

Inthelattercaseoneoxygenatom(O2,O2)isterminallyboundtotherelatederbiumions(Er,Er)andthesecondoxygen(O1,O1) is involved in a monoatomic bridge between the twolanthanideions.Eachofthetworemaininganionschelatesametalion(ErandEr).AsaresultoftheinversioncentertheEr(O1,O1)Er doublebridgingnetworkisperfectlyplanar.ThesecondbridgethroughtheatomsO4,Er,O5,O4,Er,and O5 is not planar. The dihedral angle between the twoplanes Er(O1, O1)Er and Er(O4, O4)Er is equal to81.58(4) whereas the erbium ions are separated by4.0093(2)a. The coordination of each lanthanide ion iscompletedtoninebytwowatermoleculesandonebidentatechelating carboxylato group. It should be noted that thephenolic OH function of the ligand is not involved in anycoordination sphere. The bridging network present in 1 isoriginal for salicylate bridges but not unprecedented if weconsidertheacetatebridges.Analmostidenticalcorehasyetbeen observed in the structure of [Ce

Versatility of the Nature of the Magnetic Gadolinium(III)−Vanadium(IV) Interaction − Structure and Magnetic Properties of Two Heterobinuclear [Gd, V(O)] Complexes

It has been known for a long time that the magnetic exchange interaction between copper and gadolinium ions is always ferromagnetic. Very recently, three exceptions to this general trend were revealed. They involve complexes associating a gadolinium(III) ion with a copper(II) ion or with radicals of the nitroxide or semiquinone types. We want to show that this trend is more general than expected, for such a behavior can also be observed in heterobinuclear vanadyl-gadolinium complexes.

General synthesis of ‘salicylaldehyde half-unit complexes’: structural determination and use as synthon for the synthesis of dimetallic or trimetallic complexes and of ‘self-assembling ligand complexes’

Abstract Template synthesis of the ligand resulting from the monocondensation of 1,2-diaminoethane with salicylaldehyde was realized successfully in the presence of copper(II) ions and nitrogen bases (imidazole, pyridine). This ‘half-unit’ ligand, named 4-(2-hydroxyphenyl)-3-aza-3-buten-1-amino or N-(2-aminoethyl)salicylaldimine, is abbreviated as SEH or SE in its deprotonated form. This reaction can be extended to other diamines. The complex [SECuImH]ClO4 crystallizes in the monoclinic space group P21/c (no. 14) with 4 formula weights in the cell having dimensions a = 9.020(1), b = 21.293(2), c = 8.384(1) A , and β = 107.64(1)°. It presents several synthetic applications. Particular attention was paid to the dinuclear imidazole-bridged complexes, with imidazole bridges being free or included in a tetradentate Schiff base, via study of their magnetic properties. Some examples of self-assembling complexes are also given, alongwith [(SECu)4OH](ClO4)2·H2O for which magnetic results confirm the trinuclear structure.

An alternating copper(II) chain with bridging oxamidato and nitrito ligands: crystal structure and magnetic properties of [Cu(NO2)2CuL]n (L=N,N′-bis(2-methyl-2-aminopropyl) oxamide)

Abstract The reaction of the monomeric cis-oxamido copper complex CuL (L standing for N,N′-bis(2-methyl-2-aminopropyl) oxamide) with copper and nitrite ions yields a chain compound [Cu(NO2)2CuL]n resulting from the trans isomerization of the oxamide ligand. Within each chain, the Cu(II) ions are alternately bridged by one dideprotonated ligand (L)2− and two (NO2)− ions. In addition, there may be an interaction between each copper ion and a second nitrite oxygen. So, each NO2 group acts simultaneously as a μ-1,1 bridging ligand and as a chelating ligand via two oxygen atoms. The structural data support a distorted 4+2 coordination mode for the copper ions. Analysis of the thermal variation of the magnetic susceptibility shows that the exchange interaction supported by the oxamidato bridge is antiferromagnetic and two orders of magnitude larger than the interaction occurring via the NO2 groups, the sign of which is also antiferromagnetic.

Experimental proof of the existence of the «half-unit» 7-amino-4-methyl-5-aza-3-heptene-2-one (AEH). Crystal structure of a novel dibromo-bridged dicopper(II) complex (CuAEBr)2

Abstract Under suitable conditions, the single condensation of acetylacetone with ethylenediamine may occur to yield a “half-unit”, 7-amino-4-methyl-5-aza3-heptene-2-one (AEH), which has been characterized by 1H and 13C NMR. The existence of this ligand is definitively supported by a single-crystal X-ray structural analysis of di-μ-bromo-bis(7-amino-4-methyl-5-aza-3-heptene-2-onato)(1-)dicopper(II). EPR spectra give proof of spin-spin interactions between pairs of copper ions within dimers in the solid state and in solution. Low temperature spectra suggest that the interaction is antiferromagnetic.

Guanidinium Alkynesulfonates with Single-Layer Stacking Motif: Interlayer Hydrogen Bonding Between Sulfonate Anions Changes the Orientation of the Organosulfonate R Group from Alternate Side to Same Side

Hydrolyses of HC[triple bond]CSO3SiMe3 (1) and CH3C[triple bond]CSO3SiMe3(2) lead to the formation of acetylenic sulfonic acids HC[triple bond]CSO3H.2.33H2O (3)and CH3C[triple bond]CSO3H.1.88H2O (4). These acids were reacted with guanidinium carbonate to yield [+C(NH2)3][HC[triple bond]CSO3] (5) and [+C(NH2)3][CH3C[triple bond]CSO3] (6). Compounds 1-6 were characterized by spectroscopic methods,and the X-ray crystal structures of the guanidinium salts were determined.The X-ray results of 5 show that the guanidinium cations and organosulfonate anions associate into 1D ribbons through R2(2)(8) dimer interactions,whereas association of these ions in 6 is achieved through R2(2)(8) and R1(2)(6) interactions. The ribbons in 5 associate into 2D sheets through R2(2)(8) dimer interactions and R3(6)(12) rings, whereas those in 6 are connected through R1(2)(6)and R2(2)(8) dimer interactions and R4(6)(14) rings. Compound 6 exhibits a single-layer stacking motif similar to that found in guanidinium alkane- and arenesulfonates, that is, the alkynyl groups alternate orientation from one ribbon to the next. The stacking motif in 5 is also single-layer, but due to interlayer hydrogen bonding between sulfonate anions, the alkynyl groups of each sheet all point to the same side of the sheet.

Mobility of the dppm ligand in dinuclear RuRh complexes: formation of trinuclear RuRh2 and RuRhCu derivatives, and X-ray structure of a new heterobimetallic hydrido-bridged complex

Abstract Protonation of RuRhH2Cl(COD)(dppm)2 (1) (COD = 1,5 cyclooctadiene, dppm = bisdiphenylphosphinomethane) with HBF4 · Et2O gives [RuRhHCl(COD)-(dppm)2]BF4 (2), which has been shown to contain two chelating dppm ligands on ruthenium and a bridging hydride (Ruue5f8H 2.08(7) A; Rhue5f8H 1.64(8) A). Complex 2 reacts with CO to give [RuRhHCl(CO)3(dppm)2]BF4 (3) containing two bridging dppm groups. Reaction of 1 with 0.5 molar equivalents of [RhCl(COD)]2 at 80°C affords the trinuclear RuRh2H2Cl(PhPCH2PPh2)(COD)2(dppm) (4) in low yield (25%), and that with CuCl at room temperature gives RuRhCuH2Cl2 (COD)(dppm)2 (5) in high yield. Complex 5 is not very stable in solution and is converted into RuCuH2Cl(dppm)2 (6), a typical adduct between a Lewis acid and a hydride complex, which can be more easily obtained from RuH2(dppm)2 and CuCl in toluene at 80°C.

Ferromagnetic interaction in a polynuclear gadolinium complex: structure and magnetic studies

Acetylsalicylic acid reacts with gadolinium(III) ions to yield a new gadolinium complex (1) displaying a chain structure which has been determined by single crystal X-ray crystallography: monoclinic P21/n n(no. 14), a n= 13.5709(13), b n= 6.7141(9), c n= 22.7232(17) nA, β n= 99.705(14)°, Z n= 4. The thermal dependence of the χMT product (χM n= molar magnetic susceptibility) has been measured and analysed according to the analytical expression of an infinite chain of classical spins derived by Fisher. The Gd⋯Gd interaction is weak but surprisingly is ferromagnetic with a magnitude of 0.037 cm−1. Modelling of the field dependence of the magnetization at 2 K corroborates this result. It should be emphasized that (1) is the first example of a polynuclear gadolinium complex displaying a ferromagnetic Gd⋯Gd interaction and having a fully determined structure.

Transition-metal complexes of cyclopentadienylphosphines XIV. Reduction reactions of various derivatives of the chelate fragment [{η5:η1-C5H4(CH2)2PPh2}MIII]2+, M = Rr Ir

Abstract Iodide abstraction by silver salts from the complexes [{η5:η1-C5H4(CH2)2PPh2}MI2], (1, M = Rh; 2, M = Ir), yields products whose structures are dependent on the coordinating ability of the anion originally associated with silver. Silver trifluoroacetate gave fully characterized disubstituted derivatives of the type [{η5:η1-C5H4(CH2)2PPh2}M(CF3COO)2], (3, M = Rh; 4, M = Ir), in which the trifluoroacetate anions are bound in a monodentate fashion. Silver hexafluorophosphate gave a dinuclear dicationic compound [{{η5:η1-C5H4(CH2)2PPh}2}Rh (μ−1)}2][PF6]2, 5, in which the metal atoms are bridged by iodide. Complex 3 crystallizes in the triclinic space group P 1 with two molecules in the unit cell, with a = 8.3060(7) A , b = 18.289(2) A , c = 7.9724(8) A , α=94.178(8)°, β = 106.477(8)°, γ = 93.964(7)° and V = 1153.2(2) A 3 . Least squares refinement leads to conventional R values R(Fo) = 0.041 and Rw = 0.042 for 3361 reflections having 1 > 3σ(1). Complex 5 crystallizes in the monoclinic space group P21/c with two molecules of 5 and two molecules of acetone in the unit cell, the dimensions of which are a = 13.838(1) A , b = 13.403(1) A , c = 14.362(1) A , β = 104.73(1)° and V = 2576.2(5) A 3 . Least squares refinement leads to conventional R values R(Fo) = 0.034 and Rw = 0.040 for 2246 reflections having 1 > 2σ(1). Surprisingly, the treatment of the bis-trifluoroacetato complexes 3 and 4 with lithium triethylhydroborate yields quantitatively the ethylene metal(I) derivatives [{η5:η1-C5H4(CH2)2PPh2}M(C2H4)], (9, M = Rh; 10, M = Ir), whereas unstable polyhydride derivatives result from the reaction of the diiodo complex 1 with lithium triethylhydroborate, and from the reaction of the bis-trifluoroacetato complex 3 with sodium tetrahydroborate. The chemical or electrochemical reduction of complex 5 leads to the solvated rhedium(III) species. [{(η5:η1-C5H4(CH2)2PPh2}RhI(THF)][PF6], 6, together with a dinuclear rhodium(II) species. [{{η5:η1-C5H4(CH2)2PPh2}RhI}2], 7. The protonation of 7 with tetrafluoroboric acid affords the monocationic dinuclear complex [{{η5:η1-C5H4(CH2)2PPh2}RhI}2}H][BF4], 8, in which the added proton bridges the rhodium atoms.