Neil F. Curtis

Some Di- and Tri-nuclear Compounds of Copper(II) with 4-Amino-4-methylpentan-2-one Oxime; Structures and Magnetism

Green [{Cu(amox)(amoxH)}2](NO3)2 (amoxH = 4-amino-4-methylpentan-2-one oxime) has twofold symmetrical, oximato-bridged, dinuclear cations. Each copper(II) ion is bonded to the nitrogen atoms of one bidentate amox – and one bidentate amoxH (marked *) ligand {Cu–Namine 2.039(4), 2.006(4)* A and Cu–Noxime 1.975(5), 2.192(5)* A}. The dinuclear cations have bonds between each copper(II) ion and the oximato oxygen atom of the other (marked #) unit {Cu–O# 2.062(4) A, Cu–Cu# 3.801(5) A}. The copper(II) ion is in asymmetrical trigonal-bipyramidal coordination, with Namine*–Cu–Noximate axial {176.5(2)˚}, and Namine–Cu–O# {136.6(2)˚}, Namine–Cu–Noxime* {126.2(2)˚} and Namine–Cu–O# {96.9(2)˚} equatorial [orthorhombic, Pbcn, a 12.218(1), b 23.361(3), c 12.275(1) A, Z 4, R1 0.057 for 2239 reflections]. The magnetic susceptibility values follow the Curie Weiss relation, with q = –10(2) K. Dark-green [{{Cu(amox)}3O}2H] (ClO4)3·3H2O has threefold symmetrical trinuclear cations, with each copper(II) ion chelated by the amine {Cu–N 1.977(3) A} and oxime {Cu–N 1.994(2) A} nitrogen atoms of one amox – ligand, and coordinated by the bridging oximato oxygen atom of another amox – ligand {Cu–O# 1.938(2) A}. A central oxygen atom on the threefold axis completes square-planar tetracoordination about each copper(II) ion {Cu–O 1.910(1) A}. Cu–Cu# distances are 3.283(2) A, with the central oxygen atom 0.233(2) A out of the Cu3 plane. Two of these tri-nuclear cations are linked confacially by a proton on the common threefold axis {O–O# 2.474(1) A}, to form novel hexanuclear clusters, with dihedral angles about the central Cu–O–O#–Cu# axis of 37.4(1)˚. Distances Cu–Cu# between the triangles are 3.180(5), 3.860(5) and 4.738(5) A [trigonal, R3 – c, a 23.932(5), c 18.581(4) A, Z 12, R1 0.034 for 1660 reflections]. The magnetic susceptibility values indicate extensive antiferromagnetic spin-coupling within the triangles. A blue compound of stoichiometry Cu(amox)(H2O)(NO3) has susceptibility values supporting a di-nuclear spin-coupled structure.

Structural studies on co-ordinated macrocyclic ligands. Part III. Preparations and crystal structure analyses of salts of the nickel(II) complex C-rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane, [Ni(tetb)]2+, in the α-, β-, and γ-configurations

The preparations and X-ray structural analyses of three configurational isomers of the [Ni(tetb)]2+ complex cation are described: [Ni(α-tetb)](ClO4)2, a= 19·298(9), b= 17·34(1), c= 14·078(6)A, space group Pbca; (Ni)(β-tetb)ZnCl4,H2O, a= 19·442(8), b= 9·926(4), c= 12·657(7)A, space group Pna21: [Ni(γ-tetb)](ClO4)2, a= 17·08(2), b= 9·01(1). c= 8·19(1)A,β= 107·1(2)°, space group P21/a. The structures of the α- and β-isomer were solved from diffractometer data and of the γ-isomer from photographic data by the heavy-atom method. The structures were refined by least-squares techniques to R 0·071 (α,1 536 reflections), 0·039 (β, 1698 reflections), and 0·075 (γ, 1184 reflections). All are co-ordinatively planar and thus strained with respect to the preferred conformation attained by co-ordination of the ligand to adjacent octahedral sites. The strain induced in the macrocycle is particularly manifest in the α-isomer in the distortion of both six-membered chelate rings, in the β-isomer by the distortion of the five-membered rings, and in the γ-isomer by distortion of just one six-membered ring. Details of these deviations from preferred geometry are presented and discussed.

A Copper(II) Compound of a Tetradentate Amine Imine Ligand with Coordinated Tetrachlorozincate Ion

Reaction of bis(ethane-1,2-diamine)copper(II) chloride with acetone in the presence of zinc(II) chloride yields m-chloro-trichloro-2K3Cl-(4,6,6-trimethyl-3,7-diazanon-3-ene-1,9-diamine-1K4N,N¢,N¢¢,N¢¢¢)copper(II)zinc(II). This has copper(II) coordinated by the tetradentate triamine monoimine ligand NH2–(CH2)2–N=C(CH3)– CH2–C(CH3)2–NH–(CH2)2–NH2. The coordination geometry is pyramidally distorted square planar, with trans N–Cu–N angles of 167.5(2) and 178.8(2)˚, and Cu–N distances for primary amine 2.001(4) and 2.007(4), secondary amine 2.011(4) and imine 1.988(4) A. One chloride ion of the [ZnCl4]2– ion is weakly coordinated axially (Cu···Cl 2.679(1) A, Cu···Cl–Zn 110.83(6)˚ with supporting N–H···Cl hydrogen bonds between the two primary amine groups and two further chloride ions of the ZnCl4 2– ion [C10H24Cl4CuN4Zn, Mr 471.04, orthorhombic, space group Pna21, a 11.418(1), b 15.392(2), c 10.723(2) A, Z 4, R1 = 0.030 for 2039 reflections with I > 2s(I)].

Structural studies on co-ordinated macrocyclic ligands. Part I. Crystal and molecular structure of [(1RS,3SR,8RS,10SR)-3,5,7,7,10,12,-14,14-octamethyl-1,4,8,11-tetra-azacyclotetradeca-4,11-diene]nickel(II) perchlorate

The X-ray structural analysis of the title compound has been determined from diffractometer data and refined by least-squares to R 0·08 for 2211 independent reflexions. Crystals are monoclinic, space-group P21/c, a= 16·401(4), b= 10·856(6), c= 15·072(4)A,β= 91·07(3)°, Z= 4. In the complex cation the two secondary amine and two imino-donor groups are in trans planar co-ordination. The two asymmetric carbon centres and the two asymmetric nitrogen centres occur in racemic pairs, the configuration of the racemate being (1RS, 3SR, 8RS, 10SR).

Structural studies on co-ordinated macrocyclic ligands. Part II. Crystal and molecular structure of acetylacetonato-C-meso-(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane)nickel(II) perchlorate

The title compound and the corresponding cobalt(III) compound have been prepared and the crystal and molecular structure of the former has been determined fromX-ray diffractometer data. Crystals are monoclinic,a= 16·190(8), b= 12·678(7), and c= 13·197(6)A, β= 100·52(8). Space group Cc. The structure was solved by the heavy-atom method and refined to R0·0630 for 1580 independent reflections. The nickel(II) ion is in approximately octahedral co-ordination with the macrocycle folded at N(4) and N(11) to occupy four adjacent co-ordination sites, a symmetrical, planar acetylacetonato-chelate occupying the two remaining sites. In the structure the configuration of the amine is 1RS, 4RS, 7RS, 8RS, 11RS, 14SR. The five-membered chelate rings adopt unsymmetrical gauche conformations and the six-membered chelate ring including N(1) and N(11) adopts a chair conformation. That containing N(4) and N(8) adopts a twist-boat conformation which minimises non-bonded interactions of the methyl substituents. The strain inherent in this non-optimum geometry is considered to be responsible for the observed low stability of compounds in which the amine has this configuration.