Jacqueline Vaissermann

Molecules to build solids: high TC molecule-based magnets by design and recent revival of cyano complexes chemistry

Abstract This paper was presented as a session lecture at the XXXIII ICCC in Florence (29 August–4 September 1998). It intends to point out some recent achievements in the chemistry and physics of transition metal polycyanides in the field of molecular magnetism. Prussian blue is sometimes considered as the first coordination compound and the paper shows how it is possible to obtain brand new results with Prussian blue analogues when looking at these antique systems with fresh eyes. Hexacyanometalates revealed in the last few years as very flexible molecular precursors to build three-dimensional molecule-based magnets with tunable and high Curie temperatures or to grow high nuclearity clusters with tunable high spins and anisotropy. The use of a localized electron orbital model allowed the authors’ team to push the Curie temperatures from 5.6 K in the Prussian blue itself to above room temperature in a vanadium–chromium Prussian blue analogue. Several groups confirmed the result and are improving it. In the same way, high spin molecules with ground spin states ranging from S=3/2 to 27/2 were obtained. The paper reviews some of the steps which lead to these spectacular findings and some of the prospects opened in molecular materials by this revival of polycyanide chemistry.

Facile route to ferrocifen, 1-[4-(2-dimethylaminoethoxy)]-1-(phenyl-2-ferrocenyl-but-1-ene), first organometallic analogue of tamoxifen, by the McMurry reaction

Abstract As part of the search for tamoxifen substitutes that could be useful in the treatment of breast cancer, the use of organometallic complexes has been investigated. For this purpose a synthesis has been developed for ferrocifen, the prototype of this new series of complexes. Low valent titanium-mediated (TiCl4/Zn) cross-coupling of 4-MeO-C6H4COPh with ferrocenyl ethyl ketone affords the corresponding but-l-ene in high yield (66%), from which ferrocifen, 3, is rapidly prepared in an overall yield of 41%.

Cyanide-bridged Fe(III)–Co(II) bis double zigzag chains with a slow relaxation of the magnetisation

Reaction of [Fe(III)(bipy)(CN)4]- with fully solvated M(II) cations [M = Co (1) and Mn (2)] produces the isostructural bis double zigzag chains [[Fe(III)(bipy)(CN)4]2M(II)(H2O)] x MeCN x (1/2)H2O; 1 exhibits intrachain ferromagnetic and interchain antiferromagnetic couplings, slow magnetic relaxation and hysteresis effects.

A chromium(III) nickel(II) cyanide-bridged ferromagnetic layered structure with corrugated sheets

An infinite stair-like layered ferromagnetic system is obtained from the reaction of K3[CrIII(CN)6] with [NiII-(cyclam)][ClO4]2(cyclam = 1,4,8,11-tetraazacyclotetradecane); a quasi-two-dimensional magnetic behaviour is suggested by the absence of three-dimensional magnetic order down to 2 K.

Cerium(III) Complexes with Lacunary Polyoxotungstates. Synthesis and Structural Characterization of a Novel Heteropolyoxotungstate Based on α-[SbW9O33]9− Units

Several cerium(III) complexes with lacunary polyoxotungstates α-B-XW9O9−33 (X=AsIII, SbIII) and W5O6−18, have been synthesized and characterized by single-crystal X-ray analysis, elemental analysis and IR spectroscopy. The X-ray analysis of Na25[Ce(H2O)5As4W40O140]⋅63H2O (1) reveals the framework of the well-known [As4W40O140]28− anion with a {Ce(H2O)5}3+ unit in the central site S1. The anion in (NH4)19[(SbW9O33)4{WO2(H2O)}2Ce3(H2O)8(Sb4O4)]⋅48H2O (2) consists of a tetrahedral assembly of four α-B-SbIIIW9O9−33 units connected by two additional six-coordinate tungsten atoms, three nine-coordinate monocapped square-antiprismatic cerium atoms and a Sb4O4 cluster. The CeIII center in the [Ce(W5O18)2]9− anion in Na9[Ce(W5O18)]⋅NaCl⋅30H2O (3) displays the square-antiprismatic environment observed in all complexes of the type [Ln(W5O18)2]n−.

Selective estrogen-receptor modulators (SERMs) in the cyclopentadienylrhenium tricarbonyl series: Synthesis and biological behaviour

A series of organometallic antiestrogens based on the OH‐tamoxifen (OH‐Tam) skeleton and bearing the (η5‐C5H4)ReI(CO)3 unit has been prepared by using McMurry coupling for the purpose of studying their biological behaviour. The cyclopentadienylrhenium tricarbonyl moiety is indeed stable in biological media, compact, lipophilic and easy to handle. Furthermore, this study allowed us to select the best candidates for subsequent use as radiopharmaceuticals either for imaging or therapy by using appropriate radionucleides, namely 99mTc and 188Re. In these molecules the β‐phenyl group of OH‐Tam has been replaced by the (η5‐C5H4)Re(CO)3 moiety, and the length of the dimethylamino side chain O(CH2)nN(CH3)2 was varied (n=2, 3, 4, 5 and 8). The compounds 7 a–7 e were obtained as mixtures of their Z and E isomers, which could be separated by semipreparative HPLC. Unlike their ferrocene homologues, the compounds do not isomerise in solution. Structural identification was carried out with NMR spectroscopy by using the HMBC and NOE techniques and was confirmed by the X‐ray structural determination of (E)‐7 a (n=2). These molecules were more lipophilic than OH‐Tam (log Po/w=4.5–6.3) and they were all reasonably well recognized by the two forms of the estrogen receptor (ERα and ERβ). For example, (Z)‐7 b (n=3) has high relative binding affinity (RBA) values of 31 % for ERα and 16.8 % for ERβ. The antiproliferative effects of two pairs of isomers, (Z)‐ and (E)‐7 b (n=3) and (Z)‐ and (E)‐7 d (n=5), were studied at a molarity of 1 μM on two breast‐cancer cell lines, MCF7 (ERα positive) and MDA‐MB231 (ERα negative). These molecules had an antiproliferative effect on MCF7 cells slightly higher than that of OH‐Tam and no effect on MDA‐MB231 cells. Thus, the antiproliferative effect observed on the MCF7 cells seemed essentially to be linked to an antiestrogenic effect. Molecular modelling studies have allowed us to rationalise these effects and select the best compounds for future development of a radioactive series.

[Cr(AA)(C2O4)2]− and [Cu(bpca)]+ as building blocks in designing new oxalato-bridged CrIIICuII compounds [AA=2,2′-bipyridine and 1,10-phenanthroline; bpca=bis(2-pyridylcarbonyl)amide anion]

Abstract The monouclear complex PPh4[Cr(bipy)(ox)2]·H2O (1) and the heterodinuclear compounds [Cu(bpca)(H2O)Cr(bipy)(ox)2]·2.5H2O (2) and [Cu(bpca)(H2O)Cr(phen)(ox)2]·2H2O (3) [PPh4+=tetraphenylphosphonium cation, bpca=bis(2-pyridylcarbonyl)amide anion, ox=oxalate dianion, bipy=2,2′-bipyridine and phen=1,10-phenanthroline] have been synthesized and characterized by single-crystal X-ray diffraction. Discrete [Cr(bipy)(ox)2]− mononuclear anions and tetraphenylphosphonium cations are present in 1 whereas the structures of 2 and 3 are made up neutral oxalato-bridged bimetallic CrIIICuII units. The chromium environment is distorted octahedral in the three complexes: two nitrogen atoms from a bidentate bipy (1 and 2) or phen (3) ligand and four oxygen atoms from two oxalate groups (1–3) build the coordination polyhedron around the chromium atom. The CrN(bipy) [2.055(3) and 2.078(3) A for 1 and and 2.060(3) and 2.066(3) A for 2] and CrN(phen) bond lengths [2.056(5) and 2.069(5) A (3)] are somewhat longer than the CrO(ox) ones [values in the ranges 1.944(2)–1.955(2) (1), 1.948(2)–1.960(2) (2) and 1.945(4)–1.953(4) A (3)]. The copper atom in 2 and 3 exhibits a distorted square-pyramidal surrounding: three bpca-nitrogen atoms [values of the CuN(bpca) bonds in the ranges 1.922(3)–2.017(3) (2) and 1.918(5)–2.004(6) A (3)] and a water molecule [CuOw=1.952(3) (2) and 1.952(5) A (3)] define the equatorial positions whereas an oxalate-oxygen atom occupies the axial site [CuOox=2.253(2) (2) and 2.325(4) A (3)]. The oxalate bridge in 2 and 3 exhibits a unusual bidentate/monodentate coordination mode, the metalmetal separation across this bridge being 5.283(1) (2) and 5.407(1) A (3). Magnetic susceptibility measurements of 1–3 in the temperature range 1.9–290 K reveal a Curie law behavior for the three complexes. The preparation of bimetallic systems by using [Cr(AA)(ox)2]− (AA=α-diimine type ligand) as a complex ligand towards coordinatively unsaturated metal complexes is analyzed and discussed.

Carbon monoxide as a building block in organic synthesis. Part V. Involvement of palladium-hydride species in carbonylation reactions of monoterpenes. X-ray crystal structure of [Ph3PCH2CHCHPh]4[PdCl6][SnCl6]☆

Abstract A palladium precursor and SnCl 2 as cocatalyst were used under 4 MPa of carbon monoxide for the catalytic alkoxycarbonylation of several monoterpenes into C 11 esters. The active catalyst involves a palladium-hydride species whose formation was investigated. In the case of the model substrate 3-phenylpropene, the source of the hydrido ligand was determined to be the alkene itself. Allylic hydrogen abstraction seems to be a general way to produce the active hydridopalladium species since monoterpenes having labile allylic hydrogens were converted under exceptional mild conditions. An X-ray crystal structure analysis was carried out on [(Ph 3 PCH 2 CH MPh) 4 (PdCl 6 )(SnCl 6 )]. kw]Palladium; X-ray structure; Terpenes; Carbonylation; Hydroesterification

Asymmetric synthesis of pipecolic acid derivatives

Abstract Condensation of chiral N-homoallyl β-amino alcohols with glyoxal produces iminium ions which are cyclized with complete stereoselectivity. These substrates, whose reactivity is closely dependent on the substitution pattern of the ethylenic moiety, undergo ene-iminium cyclizations that ultimately lead to homochiral pipecolic acid derivatives.

Cobalt(III) Complexes with Carboxamido‐N and Sulfenato‐S or Sulfinato‐S Ligands Suggest that a Coordinated Sulfenate‐S is Essential for the Catalytic Activity of Nitrile Hydratases

A bis(sulfenato-S)CoIII complex and its corresponding bis(sulfinato-S) complex were prepared. Their catalytic nitrile hydration activity was tested. Whereas the former catalyzes the hydration of CH3CN under mild acidic conditions, the latter is inactive. A mechanism for this reaction is proposed, in relation with nitrile hydratase activity.