E. Donald Mckenzie

Metal(III) compounds of potentially septadentate[N4O3] ligands derived from tris(2-aminoethyl)amine and substituted salicylaldehydes. Part I. Preparation of gallium, chromium, manganese, iron, and cobalt compounds, and the crystal and molecular structure of the iron compound of tris[2-(5-chloro-2-hydroxybenzylidene)ethyl]amine, [Fe(C27H24Cl3N4O3)]·3H2O

The potentially septadentate and trianionic Schiff base ligands, prepared from tris(2-aminoethyl)amine and three moles of salicylaldehyde, react with GaIII, CrIII, MnIII, FeIII and CoIII species to form 1 : 1 neutral compounds. This paper reports a range of such compounds, prepared from substituted aldehydes (3-OMe, 3-NO2-, 5-Cl, 5-Br, 5-OMe, and 5-NO2) as well as the parent salicylaldehyde; details are given of their electronic spectra; some polymorphs and isomorphous series are classified from the X-ray powder diffraction patterns; and a full X-ray structural analysis of the iron(III) compound of the 5-chloro-substituted ligand is reported. Crystals of the latter were cubic with a = 22.497(1)A, space group la3 (Tn7, No. 206). Data were collected by diffractometer, and the structure solved from 1 081 independent reflections by conventional Patterson and Fourier techniques; it was refined by block-diagonal least-squares to a final R of 0.060. The molecule is essentially an [Fe(O3N2)] octahedral species [Fe–O 1.953(6), Fe–N 2.185(7)A], lying on a three-fold crystallographic axis. The latter passes through the iron and the other (apical) nitrogen N(1), which appears to be antibonding with respect to the metal. This nitrogen is 3.26(2)A, from the metal atom, and almost co-planar with its three carbon-atom substituents. C–N(1)–C anglesare 117.8 (15)°; and N(1) isonly 0.2A below the C3plane. Thewater molecules, in the crystal, form a flattened octahedral set about the crystallographic C3 axis, hydrogen-bonded to themselves and to the phenolic oxygens of the ligand.

Steric strain in cobalt(III) compounds. Crystal and molecular structure of dibenzoylmethanato-O,O′-[NN′-o-phenylenebis(salicylideneiminato)]cobalt(III)

A preparative study is reported of the mixed-ligand cobalt(III) compounds with β-diketonate or related ester anions and the quadridentate ligand of the title compound. Although the quadridentate ligand was expected to remain in a planar configuration in such compounds, several β-diketonate species can be made in which the diketone is O,O-bidentate and the quadridentate ligand is in the same non-planar configuration that NN′-ethylenebis(salicylideneiminate) adopts in related compounds. This is proven, and the details of the steric strain in the molecule are revealed, by an X-ray structural study of the title compound. The orange-brown crystals are monoclinic with a= 16.89(2), b= 16.47(1), c= 9.84(1)A, β= 90.86(5)°, space group P21/n, and Z= 4. A total of 3 091 independent reflections were obtained on a diffractometer. The structure was solved by conventional Patterson and Fourier techniques and was refined to a final R of 0.059. The octahedral cobalt(III) molecular species contains an O,O-bidentate β-diketonate anion, and the quadridentate Schiff-base ligand is in the non-planar cis-β configuration. The steric strain is taken up not only in the expected bond-angle distortions, but also in significant bond-length changes. Whereas the two Co–N distances are not significantly different [1.906(4) and 1.902(5)A], nor are the two Co–O distances for the β-diketonate [1.897(4) and 1.894(4)A], yet the two Co–O distances for the quadridentate ligand differ by 8σ. The distance to the ‘out-of-plane’ oxygen is long [1.912(4)A] and that to the ‘in-plane’ oxygen is shorter than normal [1.880(4)A]. Bond angles at the cobalt range between 83.5(2) and 96.5(2)°. In contrast to the diketonates, both ethyl acetoacetate and diethyl malonate form C-bonded unidentate compounds, with the quadridentate ligand in the planar configuration.

The mixed ligand cobalt(III) compounds of β-diketonates and quadridentate dianion Schiff bases

A structural study is reported of the mixed chelate compounds of cobalt(III) with the quadridentate dianion ligand NN′-ethylenebis (salicylideneiminate)(salen and some methyl substistuted analogues) and some potentially bidentate monoanion ligands: β-diketonates, salicylaldehyde, and ω-nitroacetopheone. Structures in soluton have been correlated with solid state structures, now known from recent three-dimemsioanl X-ray crystallographic studies. Roliance is largely on n.m.r(1H and 19F) data, with some help from the i.r and visible and u.v electronic spectra. The compounds generally have a distored octahedral six-co-ordinate structure with a non-planar strained salen moiety. Evidence is reported for isomers of many of the compounds and their interconversion, giving equilibrium mixtures in solution. Their range of stability has been investigated, and it is shown that in donor solvents reaction occurs giving the species [Co(salen)(solvent)2][β-diketonate] in which the quadridentate ligand its more stable, essentially planar structure. No evidence could be found for species in which the β-diketonate is bonded to the metal in an alternative mode through the methylene carbon atom.

The crystal and molecular structure of a paramagnetic, five-co-ordinate cobalt(III) compound : {NN′-bis[α-(2-amino-5-chlorophenyl)benzylidene]-ethane-1,2-diaminato(2-)-NN′N″N‴}chlorocobalt(III)–chloroform–dichloromethane (1/0.5/0.5)

Crystals of the title compound are monoclinic, a= 6.92(2), b= 16.19(5), c= 26.69(8)A, β= 95.3(1)°, space group P21/c. A three dimensional X-ray analysis of the structure was made with counter data (1 303 independent reflections). The structure was solved by conventional Patterson and Fourier methods and refined by block-diagonal least squares to R 0.088. The [Co(N4)Cl] co-ordination polyhedron is square pyramidal (Co–N 1.84–1.92 A); the cobalt atom lies 0.19 A out of the N4 plane in the direction of the axial chlorine atom; there is an unusually long Co–Cl bond [2.507(2)A]. The quadridentate ligand has a stepped conformation with the phenylene moieties approximately parallel and inclined at 173.9 and 172.6° to the N4 plane; the central chelate ring has a symmetrical gauche conformation.

Crystal and molecular structure of a solvate of chloro-[1,6-bis-(2′-pyridyl)-2,5-diazahexane]copper(II) chloride

The structure of the α-form of the title compound has been determined by a three-dimensional X-ray structural analysis. Crystals are monoclinic with a= 9·73(1), b= 13·66(1). c= 14·52(1)A, β= 112·95(5)°, space group P21/c, and Z= 4. The structure was solved by conventional Patterson and Fourier techniques and refined by block-diagonal least-squares methods to a final R of 0·102, for 1246 independent reflections collected on an automatic diffractometer. The cation is five-co-ordinate with a geometry approximating to a square pyramid. One of the pyridyl nitrogens occupies the axial position with Cu–N 2·21 (2)A. The other bond lengths are normal, although there are distortions of the co-ordination polyhedron resulting from ligand constraints, and some distortions of bond angles in the chelating ligand itself. The chloride anions form hydrogen-bonded ‘bridges’ between secondary amine nitrogens of screw-related cations. The solvent (water or methanol) is disordered in regions around centres of symmetry; water and/or methanol can be accommodated with small variations of the unit-cell dimensions.

Cobalt(III) compounds of carbanions and their reactivity. Part II. Crystal and molecular structure of malononitrilato[propane-1,2-bis(salicylideneiminato)]pyridinecobalt(III)

The structure of the title compound has been determined by a three-dimensional X-ray structural analysis. Crystals were monoclinic with a= 9·25(3), b= 18·14(6), c= 14·00(4)A, β= 105·3(1)°, space group P21/c, and Z= 4. The structure was solved by conventional Patterson and Fourier techniques, and was refined anisotropically by block-diagonal least-squares methods, using of 1369 independent reflections, collected on a diffractometer, to a final R of 0·061. This analysis confirms the presence of a Co–C bond [2·02(1)A] in the six-co-ordinate cobalt(III) molecule, and trans to it is a long cobalt to pyridine bond [Co–N 2·06(1)A]. The four donor atoms of the quadri-dentate ligand are in an essentially planar array with normal bond-lengths [Co–O 1·89(1) and 1·88(1); Co–N 1·91(1) and 1·88(1)]. There is disorder in the 1,2-di-iminopropane chelate ring, which appears to include methyl groups which must be axial substituents on nonsymmetrical chelate rings.

Crystal and molecular structure of chloro[NN′-di-(3-aminopropyl)-piperazine]nickel(II) chloride

The structure of the title compound has been determined by a three-dimensional X-ray structural analysis, by use of 1967 independent reflections obtained photographically. Crystals are monoclinic with a= 7·85(3), b= 14·47(3), C= 14·14(3), β= 110·00(5)°, space group P21/c, and Z= 4. The structure was solved by conventional Patterson and Fourier techniques and refined by block-diagonal least-squares methods to R 0·084. The cation is five-co-ordinate with a geometry approximating to a square pyramid. The four nitrogens of the tetra-amine are closely co-planar, with the nickel 0·34 A out of this plane towards the covalently bound chlorine [Ni–N(primary) 2·103(7) and 2·107(7); Ni–N(tertiary) 2·052(8) and 2·053(8); Ni–Cl 2·338(3)A]. The N4 plane, however, is distorted from a square by ligand constraints, so that N–Ni–N angles (between adjacent nitrogens) are 72·0(3)–95·2(3)°. Bond lengths within the cation have normal covalent values; the chloride ion forms a specific hydrogen-bonded ion-pair with the cation so as to be near the (sterically hindered)‘sixth co-ordination site’ of the nickel [Ni–Cl 3·395(3)A]. The analysis shows the steric over-crowding of the ligand system (B-strain) which accounts for the low stability constants of its metal compounds.

Crystal and molecular structure of 1,3-bis(2-iminobenzylideneimino)-propanenickel (II)

Crystals of the title compound are orthorhombic with a= 7·69, b= 24·42, and c= 7·94 A, space group Pnma(D2h16, no. 62). A three-dimensional X-ray analysis of the structure was made with Weissenberg photographic data, estimated visually (783 independent reflections). The structure was solved by conventional Patterson and Fourier methods and refined by block-diagonal least-squares to a final R of 0·069. The [NiN4] co-ordination polyhedron [Ni–N = 1·860(7) and 1·923(7)A] is essentially planar (Ni atom 0·04 A out of the symmetry imposed N4 plane), but the molecule has an oblique-puckered conformation, with the aromatic moieties of the ligand inclined at 36·6° to one another, and the chelate ring containing the trimethylene moiety has an uncommon symmetrical ‘boat’ conformation.

Stereochemistry of bis(salicylaldiminato)metal(II) compounds. Part I. Bis[N-(2,6-dialkylphenyl)salicylideneiminato]nickel(II) compounds and five- and six-co-ordinate pyridine and picoline complexes

The compounds bis[N-(2,6-dimethylphenyl)salicylideneiminato]nickel(II), bis[N-(2,6-diethylphenyl)salicylideneiminato]nickel(II), and analogous species with substituents at the 3 and/or 5 positions of the salicyl moiety, strongly prefer the four-co-planar geometry in the solid state and in non-donor solvents. They are forced into tetrahedral structures only by bulky substitution (NO2, but not Me, OMe, Br, or Cl) at the 3 position of the salicyl moiety; and they do not form six-co-ordinate oligomers as do the N-phenyl and 3- and 4-substituted N-phenyl compounds. In pyridine and the picolines, however, in spite of bulk steric effects (B-strain), they form five- and six-co-ordinate complexes with the bases, to an extent determined by (a) the steric effect {Me > Et (on N-phenyl); and γ-pic py > α-pic}; and (b) the electron-withdrawing substituents on the salicyl moiety (NO2 > OMe > Br Cl > Me H > 5,6-benzo; and 3- > 5-). Electronic spectra (5–30 103 cm–1), bulk magnetic susceptibility, and 1H n.m.r. data (including paramagnetic shifts) have been used to define structures.