Paolo Delise

Structural effects of the co-ordination of quadridentate Schiff bases to transition-metal atoms. Structure of NN′-(o-phenylene)bis(salicylideneamine) and of its cobalt(II) complex

Geometrical variations which occur when a quadridentate Schiff-base co-ordinates to a cobalt(II) atom are compared on the basis of the crystal structure analysis of the ligand NN′-(o-phenylene) bis(salicylideneamine)(I) and its CoII derivative in its orthorhombic (II) and monoclinic (III) modifications. Crystals of (I) are monoclinic, space group P21/c, with cell parameters: a= 6.064(3), b= 16.541(7), c= 13.306(7)A, β= 91.5(1)°. Crystals of (II) are orthorhombic, space group P212121, with a= 16.755(7), b= 17.532(8), c= 5.362(3)A, and of (III) are monoclinic, space group P21/nwith a= 10.681(5), b= 8.354(4), c= 18.185(8)A, β= 105.3(1)°. A total of 1 277 (I). 1 113 (II), and 2 558 (III) independent reflexions were used : the structures were solved from diffractometer data by the heavy-atom method and refined to final R factors of 0.056 (I), 0.046 (II), and 0.041 (III). The enolimine form is established for (I) in the solid state. Upon co-ordination, with formation of (II) and (III), the geometrical data suggest that the contribution to the resonance of a ketamine form becomes as important as that of the enolimine. This is in agreementwith a π-orbital delocalization of the electronic charge over the planar complex molecule.

Quadridentate Schiff-base metal complexes as chelating ligands of alkali metals. Synthesis and structure of ammonium and sodium tetra-phenylborate addition complexes with [NN′-ethylenebis(salicylideneiminato)]nickel(II)

Transition-metal complexes of the Schiff-base NN′-erhylenebis(salicylaidimine)(H2salen) co-ordinate ammonium and alkali-metal cations to give addition complexes of different stoicheiometry. The complex [Ni(salen)] with ammonium or potassium tetraphenylborate, M′[BPh4], gives addition compounds of formula [{Ni(salen)3-,M′(BPh4)]·nL [L = solvent, e.g. tetrahydrofuran (thf), acetonitrile, or acetone]. For n= 2 and L = thf the complexes are isomorphous. Reaction with Na [BPh4] in acetonitrile yields again a compound with Ni : Na 3 : 1, from which [{Ni(salen)}2Na(NCMe)2(BPh4)]·2MeCN is obtained by very slow crystallization. The crystal structures of [{Ni(salen){3(NH4)(BPh4)]·2thf, (I), and [{Ni(salen)}2Na(NCMe)2]·2MeCN, (II), have been determined from three-dimensional X-ray data. Crystals of both compounds are triclinic, space group P, Z= 2, with cell parameters: (I), a= 18.93(1), b= 16.94(1), c= 14.84(1)A, α= 91.6(2), β= 111.4(2), γ= 116.8(2)°; (II), a= 14.64(1), b= 15.56(1), c= 14.91 A, α= 85.2(1), β= 114.2(1), γ= 98.7(1)°. The structures have been solved by Patterson and Fourier methods and refined by block-diagonal matrix least squares to R 0.11 for (I) and 0.080 for (II). The structure of (I) consists of discrete [BPh4]– anions and [{Ni(salen)}3(NH4)]+ macrocations in which the ammonium ion is surrounded by the six oxygen atoms (mean N H4+⋯ O 2.92 A) of the three Ni(salen) moieties. The co-ordination polyhedron is intermediate between a trigonal prism and an octahedron. as determined by a balance of steric and electrostatic factors. Similarly the structure of (II) has discrete [BPh4]– anions and [{Ni(salen)}2Na(NCMe)2]+ macrocations with the sodium ion on an approximately two-fold axis, co-ordinated by the four oxygen atoms of the two Ni(salen) molecules and by the nitrogen atoms of the two acetonitrile molecules occupying cis positions. The co-ordination polyhedron approximates to an octahedron with mean Na+⋯ O 2.41 and Na+⋯ N 2.49 A.

Five-co-ordinate ethylene complexes of platinum(II). Part 2. Synthesis and reactivity of some five-co-ordinate complexes of platinum with bis(hydrazones) and X-ray crystal structure of [butane-2,3-dione bis(methylhydrazone)]dichloro(η-ethylene)platinum(II)

The reaction of bis(hydrazones) with Zeises salt, K[Pt(C2H4)Cl3], to give stable five-co-ordinate complexes of general formula [Pt(C2H1)Cl2(L)] is reported [L = Ph(H)N·N:[graphic omitted]:N·N(H)Ph (L1), Ph(H)N·N:C(Me)·C(Me):N·N(H)Ph (L2), Ph(Me)N·N:C(Me)·C(Me):N·N(Me)Ph (L3), Me(H)N·N:C(Me)·C(Me):N·N(H)Me (L4), or Me2N·N:C(Me)·C(Me):N·NMe2(L5)]. These have a trigonal bipyramidal structure with the chlorine atoms in the apical positions, and the bidentate ligand (which co-ordinates through its α-di-imine unit) and the ethylene in the equatorial plane. The five-co-ordinate species decompose in solution releasing ethylene and giving four-co-ordinate complexes of formula [PtCl2(L)]. The rate of decomposition in 1,2-dichloroethane has been measured and its relationship to 1H n.m.r. data is discussed.The crystal and molecular structure of the five-co-ordinate [Pt(C2H4)Cl2(L4)] has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The structure has been refined by full-matrix least-squares techniques to a final R(on F) of 0.035 based on 712 reflections. The title compound crystallizes in the orthorhombic space group Cmcm, with four molecules in a cell of dimensions a= 7.912(7). b= 15.821 (9), and c= 10.718(8)A. The co-ordination of the platinum atom is trigonal bipyramidal, assuming the ethylene molecule acts as a umdintate ligand. One symmetry plane contains the Cl–Pt–Cl group and bisects the bis(hydrazone) and the ethylene molecules, whilst the other contains the platinum atom and all the non-hydrogen atoms of the equatorial ligands. Significant bond distances are Pt–Cl = 2 304(3). Pt–N = 2.221(10), and Pt–C = 2.073(12)A. The results suggest that the equatorial and axial covalent radii of five-co-ordinate platinum(II) resemble those of three-co-ordinate platinum(0) and four-co ordinate platinum(II) respectively.

The bonding of hydrazones in transition metal complexes. Crystal and molecular structure of trans-dichloro-ethylene-acetonemethylphenylhydrazone- and trans-dichloro-ethylene-acetaldehydedimethylhydrazone-platinum(II) complexes

Abstract The X-ray structures of trans-[Pt(C2H4)Cl2(Me2C = NNMePh)], I, and trans-[Pt(C2H4Cl2(MeHC = NNMe2)], II, have been determined. They were solved by conventional Patterson and Fourier methods giving conventional discrepancy factors of R = 0.066 for 1476 reflections in compound I and R = 0.065 for 866 reflections in compound II. Compound I crystallizes in the space group P21/c with four formula weights in a cell Measuring a = 9.488(8), b = 11.315(8), c = 14.726 (9) A; β = 105.2°; compound II crystallizes in the space group P21, with two formula weights per unit cell having a 6.652(7), b = 11.961(8), c = 7.143(7) A; β = 98.8°. Crystal densities are 1.987 g/cm3 and 2.31 g/cm3 for compound I and II respectively. The structures consist of individual monomeric molecules with the platinum atom in a four coordinate arrangement. The hydrazone molecule coordinates through the iminic nitrogen; the two nitrogen atoms and the skeleton of the carbonylic residue lie essentially in a plane which 70.3° in compound I and of 87.7° in compound II. The geometry around the aminic nitrogen, N(2), is pyramidal and in both cases its methyl substituent is directed towards the metal. The structural data are compared with those of the palladium complex trans-[PdCl2(Me2C = NNmePh)2].

Crystal and molecular structure of five-co-ordinate fumaronitrile(8-methoxycyclo-oct-4-enyl)(1,10-phenanthroline)iridum(I)

The crystal structure of the title compound was determined from three-dimensional X-ray data by conventional Fourier methods. Crystals are triclinic, space group P, with Z= 2, and cell parameters a= 9.848(6), b= 14.25(1), c= 17.93(1)A, α= 36.28(4), β= 128.5(1), γ= 125.0(1)°. Least-squares refinement, based on 1 921 independent reflexions, reduced R to 0.078. Crystals consist of discrete molecules in which the iridium (I) atom has distorted trigonal-bipyramidal stereochemistry with the phenanthroline and cyclo-octenyl ligands both spanning axial and equatorial positions; the fumaronitrile molecule occupies the remaining equatorial position. The σ-bonded carbon atom of the cyclo-octenyl ligand is axial [Ir–C 2.13(3)A] and the two olefinic linkages are equatorial with the CC bonds practically coplanar with the metal atom.

Synthesis and crystal structure of the metallacyclopentane complex 2,2,5,5-tetracyano-3-ethoxy-1,1-bis(triphenylphosphine)-1-platinacyclopentane

Reaction of [Pt(PPh3)2(C2H4)] with 1,1,2,2-tetracyano-3-ethoxycyclobutane and 1,1,2,2-tetracyano-3-(p-methoxyphenyl)cyclobutane gives the platinum-cyclopentane complexes (1)[Pt(PPh3)2{C4H3(CN)4OEt}] and (2)[Pt(PPh3)2{C4H3(CN)4C6H4OMe}]. The crystal structure of (1) was determined from diffractometer data. Crystals are monoclinic, space group P21/c with cell parameters a= 10.586(6), b= 20.422(10), c= 23.234(10)A, β= 115.23(10)°. The structure was solved by the heavy-atom method and final least-squares refinement gave R 0.092 for 2 636 reflections. The platinum atom has been inserted into a carbon–carbon bond. Three- and four-membered carbocycles are compared.