Donald F. Cook

Metal(III) compounds of potentially septadentate [N4O3] ligands. Part II. Crystal and Molecular structures of [M(C27H24Cl3N4O3]·3H2O (M = Cr, Mn)

The three dimensional X-ray structural analyses are reported of the chromium(III) and manganese(III) compounds of the trianionic Schiff base ligand derived from tris(2-aminoethyl)amine and three mol of 5-chlorosalicylaldehyde. Both are isomorphous with the previously reported Fe III compound: space group Ia 3 (No. 206) a = 22.521(2) A [Cr], and 22.490 A [Mn]. Data were collected by diffractometer {958 independent reflections for Cr (Cu-Kα radiation), and 852 for Mn (Mo-Kα radiation)}, and the structures were refined by block-diagonal least-squares to final Rs of 0.072 [Cr] and 0.050 [Mn]. Both are essentially octahedral [M(N 3 O 3 ] species, lying on three-fold crystallographic axes, and the Mn compound provides an unusual example of an undistorted octahedral d 4 system. Bond-lengths in the coordination polyhedra are: CrO 1.979(6), CrN 2.137(7), MnO 1.965(3), and MnN 2.137(4) A . Non-bonded metal to apical (tertiary) nitrogen distances are hardly different from that found in the isomorphous Fe III compound: MN = [Cr] 3.229(8), [Mn] 3.229(4), and [Fe] 3.260(4) A .

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.

Nickel(II) compounds of three homologous linear tetra-amines, especially solvent effects and configuration

Abstract A comparative study has been made of the 1:1 nickel(II) compounds of three homologous linear tetraamines: 1,4,7,10-tetraazadecane(trien), 1,4,8,11- tetraazaundecane(2,3,2-tet), and 1,5,8,12-tetraazodecane(3,2,3-tet). A range of solid compounds Ni(tetraamine)X 2 (X = Cl, Br, I, NCS, NO 2 , NO 3 , Clo 4 ), a number of which are new, has been prepared from 2,3,2-tet and 3,2,3-tet. These include the structural isomers yellow low-spin [Ni(3,2,3-tet)]I 2 ] and lilac high-spin trans -[Ni(3,2,3-tet)]I 2 ]. The high-spin species have a trans octahedral configuration, except for [Ni(2,3,2-tet)NO 3 ]NO 3 , which appears to have a chelating nitrate. In solution in water, DMF, and DMSO two equilibria of these compounds have been studied under varying conditions: (a) the cis ⇄ trans equilibria of the high-spin [Ni(N 4 )(S) 2 ] 2+ species (S = solvent); and (b) high spin octahedral ⇄ low-spin planar equilibria. It is shown for the first time that equilibria (a) occur in such solutions for both 2,3,2-tet and 3,2,3-tet. The trans isomers are preferred over cis in the orders: (i) (for solvent) H 2 O > DMF > DMSO; and (ii) (for the amines) 3,2,3-tet > 2,3,2-tet ⪢ trien. In concentrated LiNO 3 and LiClO 4 , Ni(trien) 2+ , but not the others, forms high spin cis -[Ni-(N 4 )O 2 ] species which apparently have a chelating anion. For equilibria (b) (the singlet ⇄ triplet equil.) the planar low-spin species are preferred in the order 2,3,2-tet > 3,2,3-tet > trien — an order different from that observed in (a). Difficulties in defining ϵ max for these low-spin species, and hence in quantifying the equilibria are discussed with evidence for the complication. The observations on both equilibria can be rationalised by reference to the steric effects of the amines: 3,2,3-tet has a greater preference thatn 2,3,2-tet for trans high-spin isomers, but it can less easily accomodate to the shorter NiN bond lengths in the low-spin species.

The slow isomerisation of a high-spin [Ni(tetraamine)(DMSO)2]2+ cation

In DMSO solution the [Ni(2, 3, 2-tet)DMSO)2]2+ cation (2, 3, 2-tet = 1, 4, 7, 11-tetraazaundecane) undergoes a remarkably slow trans cis isomerisation: the initially trans cation converts to an equilibrium mixture which is mainly cis.kobs(298) = 1.92 × 10−5 sec− (t1/2 ≈ 14 hr), Keq ≈ 5, kobs(138) = 4.89 ×10−5 sec−1, ΔH≠ = 8.2 (±0.5) kcal mol−1, ΔS≠ = −52.0 (±2.0) cal deg− mol−, and Ea = 8.8 (±0.5) kcal mol−1. Added water or dimethylsulphone accelerate the reaction, which seems to be unique among such tetraamine compounds. The slowness probably results from a uniquely ordered solvent shell.

Metal ion complexes of 5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetra-aza-cyclotetradeca-4,11-diene. Part I. Some nickel(II) and copper(II) compounds

Preparations and properties of nickel(II) and copper(II) complexes of the tetra-aza macrocycle (1) formed by reaction of benzylideneacetone with diaminoethane are reported. Stereochemical evidence favouring assignment of the structure 5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetra-azacyclotetradeca-4,11-diene for (1), present in the trans-trans-meso-configuration, is presented. Compounds with two configurations of the cation [Ni(1)]2+ arising from the chiral co-ordinated secondary amino-groups were isolated. The β(N-meso) configuration is optimum for planar bcde-co-ordination and singlet ground-state square-planar salts [Ni(β1)]X2, X = ClO4–, BF4–, I–, and 0·5ZnCl42– and trans-octahedral triplet ground-state compounds trans-[Ni(β1)X2], X = Cl–, NCS–, CH3CO2–, or NO3– and trans-[Ni(β1)(NH3)(H2O)](ClO4)2 were prepared. The α(N-rac) configuration is optimum for folded abcd-co-ordination and triplet ground-state compounds with chelates occupying the ef co-ordination sites, [Ni(α1)en](ClO4)2, [Ni(α1)acac]ClO4, and [{Ni(α1)}2C2O4](ClO4)2 were prepared. Treatment of these compounds with acid removed the chelate by protonation while preserving the α configuration to give square planar salts [Ni(α1)](ClO4)2 and [Ni(α1)]ZnCl4, metastable with respect to their β configurational isomers. The co-ordination stereochemistry of (1) is discussed and 1H n.m.r., i.r., and d-d electronic spectra are reported. It is concluded that the metastability of the α configuration of (1) in planar co-ordination arises from strain introduced by the presence of a phenyl group as an axial substituent on one six-membered chelate ring. The compounds [Cu(β1)]X2, X = ClO4–, NO3–, or NCS– and [Cu(β1)]Cl2,4H2O are assigned tetragonal structures. The i.r. spectra of the perchlorate and nitrate indicate weak metal-anion interactions.

Reactions of copper(II) and nickel(II) compounds of 6-methyl-2-picolylamine with acetone, including and x-ray structural analysis of [Ni(C20H28N4)(NO3)]NO3

The reaction with acetone of nickel(II) and copper(II) bis-chelated compounds of 6-methyl-2-pyridylmethylamine gives compounds of the quadridentate [N4] ligand 2,6-diaza-1,7-bis-(6′-methyl-2′-pyridyl)-3,5,5-trimethyl-hept-2-ene(Q). In the nickel series also, a bis-chelated perchlorate of the terdentate ligand 2-aza-1-(6′-methyl-2′-pyridyl)-3-methyl-hex-2-ene-5-one was obtained. In the copper series, five-coordinate species [Cu(Q)X]X (X = Br, I, NCS) and [Cu(QX]ClO4 (X = Cl) were isolated. If left in acetone, these undergo further reaction, with increasing ease in the order Cl < Br < I. An intermediate formation of a transient brown colour suggests the possible involvement of a copper(I) intermediate. The nature of the products was established by an X-ray analysis of the structure of [Ni(Q)NO3]NO3. Crystals are orthorhombic, a = 20.36(2), b = 13.38(1), c = 8.226(5) A, space group Pna21. Using two-circle diffractometer data (1598 reflections), the structure was solved by Patterson and Fourier methods, and refined by block diagonal least-squares methods to a final R of 0.030. The expected quadridentate ligand was found in the cis-β configuration about the metal, with coordination sphere completed by a bidentate nitrate. Bond-lengths and angles within the molecular cation were unexceptionable considering the small ‘bite’ of the chelated nitrato group of only 59°.

Some metal-ion complexes with ligands formed by reaction of amines with aliphatic carbonyl compounds. Part III. Some compounds formed by reaction of 1,3-diaminopropane nickel(II) compounds with acetone

Bis(1,3-diaminopropane)nickel(II) salts react with acetone to give bisisopropylideneamino-complexes, as singlet ground state salts for ClO4– and BF4– or as triplet ground state di-acido-derivatives for NO3– NCS– or Cl– In the presence of a third mol of the diamine reaction continues to yield salts of a cation with a tetradentate ligand formed from two diamine residues linked by an ‘amine-imine bridge’ derived from two acetone residues, and with an additional isopropylideneamino group. Reaction continues, the final product having a tetra-azacyclohexadeca-diene ligand formed from two diamine residues linked by two such bridges. For the nitrate, an intermediate triplet ground state compound with a pentadentate β-aminoketone ligand and one co-ordinated nitrato-group was isolated.