Jean-Pierre Laurent

New examples of dinuclear copper complexes with ferromagnetic interactions mediated by μ-1,1 bridging azido and nitrito groups: structures and magnetic properties of [L2(N3)2Cu2] and [L2(NO2)2Cu2]·H2O (L=7-amino-4-methyl-5-aza-3-hepten-2-onato(1−))

Abstract The reaction of L 2 Cu 2 OAc 2 ( L = 7amino-4-methyl-5-aza-3-hepten-2-onato(−1); OAc = acetate ion) with NaN 3 and NaNO 2 yields [L 2 (N 3 ) 2 Cu 2 ] ( 1 ) and [L 2 (NO 2 ) 2 Cu 2 ]·H 2 O ( 2 ), respectively. The azido complex crystallizes in the triclinic space group P 1 with a = 8.261(1), b = 9.176(1), c = 7.915(1) A , α = 113.06(1), γ = 108.90(1)°, Z = 1 . The nitrito complex also crystallizes in the triclinic space group P 1 with a = 11.523(1), b = 11.532(1), c = 112.22(1), β = 91.33(1), γ = 92.06(1)°, Z = 2 . In both cases the structure consists of neutral dinuclear entities resulting from the pairing of two mononuclear units via single-atom bridges connecting an equatorial position of a copper centre to an axial position of the other one. The copper ions adopt a (4 + 1) square-based geometry in the azido complex while (4 + 1) and (4 + 2) environments are present in the nitrito complex. Analysis of the thermal variation of the magnetic susceptibility shows that in both complexes, the two spins are ferromagnetically coupled within the dimer while an antiferromagnetic coupling is operative between dinuclear entities. Both types of interactions are larger in the case of the azido complex ( J = 24 cm −1 , J ′ = 1.6 cm −1 ) than for the nitrito complex ( J = 8 cm −1 , J ′ = −0.2 cm −1 ).

Sur la structure des alkylcycloarsoxanes (RAsO)α

Abstract Organometallic compounds of general formula (RAsO) α are associated as trimers (R = C 2 H 5 , C 3 H 7 , C 4 H 9 ) or even as a tetramer (R = CH 3 ). Their physicochemical properties show them to be cyclic, the oxygen atoms being located in the bridging position. A “limited” electron delocalization may occur in these rings.

SPECTROSCOPIC AND X-RAY STRUCTURAL STUDY OF THE COPPER(II) COMPLEX WITH SCHIFF BASE BETWEEN PYRIDOXAL AND BENZYLAMINE

Abstract Bis(N-benzylpyridoxaldiminato) copper(II) has been prepared and studied in solution and solid state. The complex crystallizes in the monoclinic space group C2h 5 – P21/a in a cell of a = .9561(9), b = 16.605(8), c = 17.561(2) A and β = 104.14(l). Based on 3684 unique reflections, the structure was refined by fullmatrix least-squares techniques to a conventional agreement factor (on F) of R = 0.045. Each ligand is bidentate through the phenolic oxygen and the imino nitrogen atoms, leading to a tetrahedrally distorted square planar environment about the copper atom. The dihedral angle between the two chelating moieties is 35.31°. The two benzyl groups are, surprisingly, in a cis position with respect to the mean plane of the molecule. In solution, the ESR data are consistent with a distorted square planar structure around Cu. Under particular conditions two sets of ESR signal are observed, suggesting the occurrence of two species.

Carboxy uracil and some of its derivatives as complexant toward platinum. Platinum blues

Abstract Platinum complexes of 6-carboxy uracil (orotic acid), 3-methyl orotic acid and 5-nitro-orotic acid and particularly a ‘platinum-blue’ have been isolated and studied; the different complexation sites of the ligand are discussed, the orotic acid nucleus exhibiting multiplicity and interconversion of binding sites.

A dicopper complex of N,N′-bis[2,2-dimethyl-4-(2-hydroxyphenyl)-3-aza-3-buten] oxamide. Structure and magnetic behaviour of the mono hydrated form

The ligand N, N′-bis[2,2-dimethyl-4-(2-hydroxyphenyl)-3-aza-3-buten] oxamide with two identical coordination sites reacts with copper ions in its tetradeprotonated form to yield the dinuclear complex [Cu2(C24H26N4O4)]·H2O. The structure of this compound has been determined by the X-ray diffraction method. The crystals are orthorhombic with a = 11.744(1), b = 16.369(2), c = 26.340(3) A, V = 5064(1) A3, Z = 8, space group Pbca. The oxamide is in a trans conformation with two different environments for the copper centres, a (4 + 1) coordination mode for the first one and a square planar environment for the other one. The water molecule is not directly bound to a copper centre, but involved in hydrogen bonding with the two oxygen atoms of an N2O2 coordination site. Indeed, extra coordination comes from a phenolic oxygen atom belonging to an adjacent dinuclear unit. Static susceptibility measurements point to a strong intrapair antiferromagnetic exchange interaction of 2J = −520(±4) cm−1 and possibly an interpair ferromagnetic exchange interaction of 10(±5) cm−1.

Etude par resonance magnetique nucleaire de la structure de quelques composes d'addition formes par des aminophosphines avec le borine et le monoethylborane

Abstract Four equimolecular adducts between aminophosphines [(CH3)2NP(CH3)2 and [(CH3)2N)3P] and boron hydrides [BH3 and B(C2H5)H2] have been prepared and characterised. From a study of their NMR (1H, 11B and 31P) spectra it is concluded that, in spite of the presence of two different donor atoms, the actual dative bond is a phosphorus-boron one.

Scrambling reactions between boron and various phosphorus moieties: The B(NEt2)3/PCl3, B(NEt2)3/OPCl3 and B(NEt2)3/SPCl3 systems

Abstract A 31 P, 11 B and 1 H NMR study of the scrambling reactions between tris (diethylamino) boron B[N(C 2 H 5 ) 2 ] 3 and PCl 3 , OPCl 3 and SPCl 3 shows that the mixed species Q Cl 3− n (NEt 2 ) n [ Q = B, P, OP or SP and n = 1 or 2] are more favoured than would be the case if a completely random mechanism was involved. In the PCl 3 /B[N(C 2 H 5 ) 2 ] 3 system the chlorine substituents display preferential affinity for phosphorus moieties over boron centers while the reverse situation is encountered in the two other systems involving quadruply coordinated phosphorus. The Lewis acidity of boron and the effective electronegativity of phosphorus moieties may explain these trends.

Sur le Mode de Reaction Des Alkylfluorobore BRnF3-n (n = 0,1,2 et 3) Avec l'acetylacetone

Abstract The NMR spectra of alkylfluoroborane BRnF3-n (n = 0, 1, 2, 3) acetylacetone C5H8O2 systems have been studied with a view to rationalizing more accurately their behaviours. At low temperatures, the C5H8O2.BRnF3-n adduct has been characterized; however, when the temperature is increased some chelated compounds appear by elimination of HF (n = 0, 1, 2) or an alcane (n = 3). The disproportionation ability of these systems has been investigated.

Comparison (nature and biological activity) between two new blue species involving, respectively, malonamide and succinamic acid as ligands

Abstract Although the preparation of blue platinum complexes is generally achieved through the reaction of a ligand involving a HNCS group with the hydrolysis products of cis -Pt(NH 3 ) 2 Cl 2 , blue species may be obtained using M 2 PtCl 4 as platinum precursors. Two new blue species involving malonamide and succinamic acid have been prepared according to this process. They display the main characteristics of the blue species, i.e. : an absorption near 660 nm in their visible spectrum, a paramagnetic behaviour (EPR signal and platinum atoms in a nonintegral oxidation state. In both cases, solid state infrared spectroscopy gives evidence of coordination through the deprotonated amido groups. The two species have been tested for antitumor activity and toxicity using Sarcoma 180 in mice. Examination of test data shows important differences between the two compounds. For instance, malonamide blue does not significantly improve the median survival time (T/C) at doses up to 1100 mg/Kg body w. while a single dose (150 mg/Kg) of the succinamic acid species produces a 189% T/C (10% survivors). The analytical data and the physico-chemical properties of the two blue species are considered with the aim of suggesting likely explanations of the differences observed in their biological properties.