M. G. H. Wallbridge

N,N'-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine

In the title compound, C19H22N2O2, the average N⋯O separation of 2.580 (4) A is indicative of intramolecular hydrogen bonding within each salicylideneimine unit. The two aromatic rings are inclined at an angle of 68.66 (11)° and this results in a conformation which is inappropriate for quadridentate ligand activity.

Di-μ-fluoro-bis[bis(dimethyl sulfoxide)trifluorozirconium(IV)]

The title compound, (ZrF4(C2H6OS)2)2 , is a centrosym- metric fluorine-bridged dimer. The seven-coordinate Zr atoms are in a pentagonal bipyramidal environment with F atoms above and below the pentagonal plane. The av- erage Zr--F bridging distance of 2.167 (4)A, is signif- icantly longer than the terminal distances which range from 1.973 (4) to 2.001 (4) ,~,.

N1,N2-Di(p-tolyl)benzamidine, C21H20N2

The C-N bonds in the amidine skeleton show distinct amine and imine characteristics; the N-C-N bond angle is 120.8 (7) o . An E,Z configuration is observed and the solid is held together in infinite chains containing N-H...N hydrogen bonding

N,N'-Diphenylbenzamidinium nitrate

The title compound, C 19 H 17 N 2 + NO 3 - , consists of a diphenylbenzamidinium cation [Ph(H)NC(Ph)N(H)Ph] + hydrogen-bonded to a planar nitrate anion through an N-H...O interaction; both ions lie on a twofold axis. The hydrogen-bonded N...O distance is short at 2.7767 (19) A, and placing the N-H protons in calculated positions gives an N-H...O angle of 173°. There are no other significant intermolecular interactions between the ions.

2-{1-[(2-Amino-4,5-dimethylphenyl)imino]ethyl}phenol

In the title compound, C16H18N2O, the imine N⋯O separation is 2.521 (2) A, indicative of intramolecular hydrogen bonding within the salicylideneimine unit. The two aromatic rings are inclined at an angle of 50.04 (6)° with respect to one another, which results in a conformation unsuitable for meridional tridentate ligand complexation to a metal.

N1,N2-diphenylacetamidine

The structure of the title compound, C14H14N2, consists of amidine molecules hydrogen-bonded to form an alterI nating chain-like arrangement. Each molecule is bonded to two other molecules by N-H...N bonds. In each amidine N-C-N fragment, the C-N bond distances are different [1.281 (3) and 1.364 (3) A], indicating some C=N imine character in one of the bonds.

Dichloro(2,3,6,8,11,12,15,17-octamethyl-5,9,14,18-tetraazadibenzo[a,h]cyclotetradecene-κ4N)zirconium(IV) tetrahydrofuran hemisolvate

The coordination geometry of the title compound, [ZrCl 2 (C 26 H 30 N 4 )].0.5C 4 H 8 O, approximates to trigonal prismatic. The Cl atoms are coordinated to the zirconium in a cis configuration. Disordered tetrahydrofuran (THF) solvent molecules are present in the crystal structure.

A dibenzotetraaza [14] annulene

The ligand 2,3,6,8,11,12,15,17-octamethyl-5,14-dihydro-5,9,14,18-tetraazadibenzo[b,i]cyclotetradecene H 2 omtaa, C 26 H 32 N 4 ) has a pronounced saddle shape as a result of interactions between the methyl groups and the phenyl rings [the dihedral angle between the phenyl rings is 139.2 (3)°]. The overall geometry of H 2 omtaa is very similar to that of H 2 tmtaa (6,8,15,17-tetramethyl-5,14-dihydro-5,9,14,18-tetraazadibenzo[b,i]cyclotetradecene, C 22 H 24 N 4 ) [Geodken, Pluth, Peng & Busten (1976). J. Am. Chem. Soc. 98, 8014-8021]

Structure of the monomethylgallium derivative of TMTAA (dibenzotetramethyltetraaza[14]annulene)

The structure consists of a GaCH 3 unit bound symmetrically to the four N atoms of the macrocycle with the metal atom 0.65 (1) A above the N 4 plane. The four N and C(methyl) atoms form a distorted square-based pyramidal geometry around the Ga atom. The average Ga-N bond distance is 2.016 (5) A and the Ga-C distance of 1.958 (8) A is fractionally shorter than the Ga-C distance of 1.967 (2) A in Ga(CH 3 ) 3 [Beagley, schmidling & Steer (1974). J. Mol. Struct. 21, 437-444]

7-Methyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene

The title compound, C14H24N4, is known to act as a macrocyclic ligand and its conformation has been determined to facilitate future comparisons with its coordinated forms. The alphatic macrocyclic strand is disordered with respect to a mirror plane perpendicular to the pyridine ring and containing the ordered tertiary N atom; the four donor N atoms are approximately coplanar.