Dario Vitali

Carbonyl derivatives of phthalocyaninatoiron(II), especially those containing group VI axial donor atoms. Crystal and molecular structure of carbonyl(N,N-dimethylformamide)phthalocyaninatoiron(II) and mössbauer studies of some of the products

Abstract The carbonyl adduct of phthalocyaninatoiron(II), FePc, with N , N -dimethylformamide (DMF) as axial ligand, FePc(CO)DMF, was prepared by the reaction of iron carbonyls, Fe(CO) 5 or Fe 2 (CO) 9 , with o -phthaalonitrile in DMF as solvent. Several carbonyl adducts of FePc of general formula FePc (CO)L are reported, with L being a ligand with oxygen, sulphur and nitrogen donor atoms (L = tetrahydrofuran, H 2 O, CH 3 OH, dimethylsulphoxide, tetrahydrothiophene, ammonia, n-propylamine, diethylamine, triethylamine). The crystal and molecular structure of FePc(CO)DMF·DMF was investigaed by X-ray diffraction methods. The compound has a monoclinic unit cell and space group P 2 1 / n , a 9.86(1), b 17.35(3), c 19.79(4) », β 87.9(2)°, Z = 4, U 3383 » 3 , D 3 1.458 g cm −3 . The iron atom is hexacoordinated to the four inner nitrogen atoms of the macrocyle, to carbon monoxide (Fe—C distance 1.72(2) ») and to DMF (Fe—O distance 2.07(1) »). The extra DMF occupies lattice sites. All of the compounds reported in this paper are substantially diamagnetic. Mossbauer spectra show typical isomer shift parameters for the bis-adducts and for the carbonyl adduct, substantially independent of the nature of the axial ligand. The quadrupole splitting parameter of the carbonyl adducts is strongly affected by the nature of the axial ligand.

Studies on organometallic compounds with hetero multiple bridges : V. Crystal and molecular structure of the parent rhenium complex Re2Br2(CO)6(THF)2 and substituted products of tricarbonylrhenium(I) derived from it

Abstract Reactions of the tetrahydrofuran adduct Re 2 Br 2 (CO) 6 (THF) 2 with some phosphorous- and nitrogen-containing donors under mild conditions are reported, which led to the formation of substituted products of tricarbonylrhenium(I). Bromide abstraction from the THF adduct by secondary amines and CS 2 produced the dithiocarbamato derivatives Re(S 2 CNR 2 )(CO) 3 (HNR 2 ) whose behaviour in solution with CO was also investigated. Mass spectral data for some of the substituted products have been measured. The title compound crystallizes in the space group P 2 1 / n with cell constants a = 8.661(2), b = 11.251(3), c = 11.424(3) A and β = 110.36(2)°, U = 1043.67 A 3 and D calc = 2.686 g cm −3 , Z = 2. The molecule consists of a planar Re 2 Br 2 moiety, as demanded by symmetry. The two THF groups are on opposite sides of this plane and the three CO groups around each rhenium atom are arranged in a fac arrangement. The unique ReBr distances are 2.642(5) and 2.644(4)A, while the ReO distance is 2.129(31) A. The ReBrRe and BrReBr angles are 97.3(2) and 82.7(1)°, respectively. The Re⋯Re nonbonding distance is 3.967(3) A. The THF ligands consist of a nearly planar C 4 fragment (maximum deviation from planarity 0.06 A), while the oxygen is 0.348 A out of that plane, the angle defined by the C 4 plane and the COC fragment of the THF ligand being 24.99°. Final values of the discrepancy indices are R ( F ) = 0.074 and R w ( F ) = 0.095.

Bis adducts of phthalocyaninatoiron(II) with Group 6 axial donor atoms. Crystal and molecular structure of sulphur-bonded bis(dimethyl sulphoxide)phthalocyaninatoiron(II)–dimethyl sulphoxide (1/2)

The bis adducts of tetrahydrothiophen (tht) and dimethyl sulphoxide (dmso) with phthalocyaninatoiron(II), [Fe(pc)L2], have been obtained by direct combination of the components. The crystal and molecular structure of the dmso adduct, [Fe(pc)(dmso)2]·2dmso, has been solved by Patterson and Fourier methods. The crystals are monoclinic, space group P21/c, with a= 7,993(2), b= 16.175(7), c= 16.086(7)A, β= 104.53(3)°, U= 2 013 A3, Dm(flotation)= 1.45 ± 0.01 g cm–3, Z= 2, Dc= 1.454 g cm–3, R= 0.067 for 1 062 independent reflections. The iron is six-co-ordinated to the four inner nitrogens of the macrocycle and to the sulphur atom of the dmso ligands, with Fe–S 2.308(4), S–O 1.474(14), and Fe–N(average) 1.94 A. The bonding parameters of the lattice dmso present in the bis adduct have also been determined, S–O 1.443(18)A. Unsuccessful attempts to prepare some bis adducts with oxygen donors are reported.

Reaction of a tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) with dioxygen: synthesis and X-ray characterization of both the oxidation product and its precursor

Abstract The tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) Ce 4 ( O 2 CN i Pr 2 ) 12 , 1, has been synthesized and its crystal structure solved through X-ray diffraction methods. The oxidation of the cerium(III) complex by dioxygen produces the μ3-oxo tetranuclear cerium(IV) derivative Ce 4 ( μ 3 - O ) 2 ( O 2 CN i Pr 2 ) 12 , 2, which has been characterised by single crystal X-ray diffractometry. Structural rearrangements on going from the cerium(III) derivative to the corresponding cerium(IV) product have been established. This is the first case of a μ-oxo-carbamato complex being obtained by oxygenation, whereby product and precursor maintain the basic structural features.

Crystal and molecular structure of di-µ-bromo-µ-tetraphenyldiphosphane-bis[tricarbonylrhenium(I)]

The title complex has been prepared by treating P2Ph4 either with [ReBr(CO)5] at the reflux temperature of benzene or with [Re2Br2(CO)6(thf)2](thf = tetrahydrofuran) at room temperature in toluene. Three-dimensional X-ray analysis has shown this to be the first example of a diphosphane bridging two co-ordination octahedra joined by a common edge. The substance crystallizes from toluene in the triclinic system, space group P, with cell constants a= 11.110(9), b= 11.538(9), c= 12.913(9)A, α= 95.95(5), β= 102.54(5), γ= 95.92(5)°, and Z= 2. The molecule consists of two rhenium atoms linked by two bromine atoms and by a P–P bridge. The six carbonyl groups are distributed around the two rhenium atoms in two groups of three, each in a fac arrangement, thus completing the six-co-ordination. The normals to the planes defined by Re(1)–Br(1)–Br(2) and by the Re(2)–Br(1)-Br(2) intersect at an angle of 23.4°. Probably important P⋯Br interactions exist, as evidenced by the non-bonding distance of 3.49 A observed, which is ca. 0.4 A less than the van der Waals radii. The P–P bond is 2.308(6)A. Evidence is presented that the products of formula [Re2X2(CO)6(P2Ph4)](X = Cl or I) previously reported have structures probably similar to that of the present complex.

Synthesis, and crystal and molecular structure of µ-dibromo-µ-tetraphenyl-diphosphane-bis[tricarbonylrhenium(I)], a molecule containing a new type of tetraphenyldiphosphane bridge

No cleavage of the P–P bond occurs during the reaction of the tetrahydrofuran (thf) complex [Re2Br2(CO)6(thf)2] with P2Ph4 in toluene; an X-ray study shows that the resulting compound contains bridging tetraphenyldiphosphane in a unique type of bonding.

The reaction of hexacarbonylvanadium with aromatic compounds. Part 4. Properties of tetracarbonylvanadium arene cations and the crystal and molecular structure of tetracarbonyl(1,2,4,5-tetramethylbenzene)vanadium(I) hexacarbonylvanadate(1—)

Improved syntheses of the cationic arene complexes of vanadium(I), [V(CO)4(C6H6-nMen)]+, are reported together with their 1H n.m.r. spectra. An X-ray crystal and molecular structure determination of the title compound has been carried out. Crystals are monoclinic, space group P21/a, a= 18.135(5), b= 12.746(4), c= 10.025(4)A, β= 93.03(2)°, and Z= 4. R= 0.072 for 1 007 observed reflections (Mo-Kα radiation). In the cation the vanadium atom is half-sandwiched between the arene ligand and the four carbonyl groups, the latter being oriented in such a way as to become eclipsed with respect to two of the methyl groups. The [V(CO)6]– anion is a nearly regular octahedron with a mean V–C distance of 1.93 A and two sets of C–V–C angles, thus leading to a slight trigonal elongation of the octahedron.

Hexacarbonyl complexes of dirhenium(I) containing E2Ph4(E = P, As, or Sb) ligands; X-ray crystal structure of [Re2Br2(CO)6(Sb2Ph4)]

The E2Ph4 complexes of rhenium(I), [Re2X2(CO)6(E2Ph4)](X = Br, E = As or Sb; X = I, E = P, As, or Sb), have been prepared by the reactions of [Re2Br2(CO)6(thf)2](thf = tetrahydrofuran) or [Re2I2(CO)8] with the appropriate E2Ph4. The crystal and molecular structure of one of the compounds, namely [Re2Br2(CO)6(Sb2Ph4)], has been solved by X-ray diffraction methods. The crystals are monoclinic, space group P21/n, with a= 16.585(8), b= 22.036(13), c= 19.764(19)A, β= 109.34(6)°, and Z= 8. Data collection yielded 2 197 observed reflections, R= 0.040. The molecule consists of two pseudo-octahedral rhenium(I) centres joined by bromide and Sb2Ph4 bridges. Average distances include Re–Br 2.663(4), Sb ⋯ Br 3.640(3), Re ⋯ Re 3.970(2), and Sb–Sb 2.826(4)A. The rhenium–P2Ph4 complex undergoes nucleophilic attack by PPh2– to form an anionic rhenium(I) carbonyl species. The small angle of folding along the Br ⋯ Br vector produces the appearance of the number of i.r. carbonyl stretches expected for the local C2v symmetry of the Re2(CO)6 core, presumably due to a better coupling of the two Re(CO)3 moieties. Chemical evidence and mass spectral data indicate that the stability of the rhenium(I) complexes decreases with increasing atomic weight of the Group 5 donor atom.

Nucleophilic aromatic substitution of the nitro-group

The reaction of piperidine with 1,2,4-trinitrobenzene or with o-dinitrobenzene in benzene affords 2,4-dinitro-1-piperidinobenzene or 2-nitro-1-piperidinobenzene, respectively, in quantitative yield. Neither reaction undergoes base catalysis and overall second-order kinetics (first-order with respect to each reagent) were observed for a wide range of piperidine concentrations in benzene. Acid catalysis does not occur either as added p-methoxyphenol fails to affect appreciably the kinetics of the reaction of the trinitrobenzene. Comparison with the reaction of piperidine with 1-fluoro-2,4-dinitrobenzene in benzene, where pronounced catalysis by both piperidine and p-methoxyphenol has been observed, allows an interpretation of the reaction in terms of an addition–elimination mechanism with rapid expulsion of the nitro-group from the intermediate. Why the expulsion of the nitro-group from the intermediate should occur so easily is not clear, however. The recent literature concerning the nucleophilic aromatic substitution of the nitro-group is reviewed.

Electrophilic cleavage of the sulphur–sulphur bond. Kinetics of the isotopic exchange between p-chlorophenylsulphenyl chloride and pp′-dichlorodiphenyl disulphide in the dark

Kinetics of the isotopic exchange between p-chlorophenylsulphenyl chloride and the corresponding [35S2]disulphide in benzene in the dark are of the second order, first order with respect to each compound. Change to chlorobenzene as solvent results in a four-fold increase of the exchange rate. Moreover, addition of tetra-alkylammonium perchlorates in benzene dramatically accelerates the exchange which, however, remains of the first order with respect to the disulphide. Also, addition of tetra-n-butylammonium chloride does not depress the exchange rate in the presence of perchlorate salts. These results suggest a polar mechanism for the exchange in the dark which cannot involve a sulphenium ion in a kinetically important step. Rather, the sulphenyl chloride must be the electrophilic species involved in the sulphur–sulphur bond breaking.