Irvin Booysen

Monodentate imido coordination of 2-aminodiphenylamine to rhenium(V)

The complex trans-[Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre solely through a dianionic imido nitrogen, with distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re–Cl bond trans to the Re=N bond is shorter than the two equatorial Re–Cl bonds. The Re = N–C bond angle of the phenylimido moiety equals 178.7(4)°.

A trigonal-bipyramidal oxorhenium(V) complex with a bidentate nitrogen-donor ligand

The oxorhenium(V) complex [ReO(Hapb)(apb)] (1) (H2apb  = 2-(2-aminophenyl)-1-benzimidazole) was prepared by reaction of trans-[ReO2(py)4]Cl with a twofold molar amount of H2apb. The complex was characterized by spectroscopy and X-ray crystallography. The results show that the rhenium atom lies in a distorted trigonal-bipyramidal environment, with the two imidazole nitrogen atoms in apical positions, and the oxo and two amido nitrogens in the trigonal plane.

Imido, amino and amido coordination of diaminouracil to rhenium(V)

Reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3-dimethyl-2,4-dioxopyrimidine (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2] (ReO4) (1). A single-crystal X-ray crystal structure shows that ddd is coordinated as a monodentate through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated as a bidentate via a neutral amino nitrogen atom, trans to the imido nitrogen, and a singly deprotonated amido nitrogen atom, trans to the iodide.

SYNTHESIS AND CRYSTAL STRUCTURE OF AN UNUSUAL MIXED CRYSTAL CONTAINING AN OXORHENIUM(V) AND IMIDORHENIUM(V) COMPLEX

An unusual mixed crystal of a square-pyramidal oxorhenium(V), [ReOCl(Hdua)], and an octahedral imidorhenium(V) complex, [Re(dua)Cl2(PPh3)], was prepared from the reaction of trans-[ReOCl3(PPh3)2]_and (6Z)-6-(2-aminobenzylideneamino)- 5-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione (H3dua) in ethanol. Characterization was performed by single crystal X-ray structure determination and IR spectroscopy. The chelate Hdua is coordinated as a tridentate diamido-imine, and dua is chelated as an imido-imino-amide.

Synthesis and characterization of a neutral rhenium(V) complex containing a tridentate chelate with an imido donor atom

The six-coordinate complex cis-[Re(mps)Cl2(PPh3)] (1) (H3mps = N-(2-amino-3-methylphenyl)-salicylideneimine) was prepared the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The compound was characterized by spectroscopy and single-crystal X-ray crystallography. Mps coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the phenolate oxygen atoms. The imide and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.

Synthesis and crystal structure of a rhenium(V) complex containing a tridentate imido-coordinated Schiff base

The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (1) (H3mps = N-(2-amino-3-methylphenyl)salicylideneimine) was prepared by reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The compound was characterized by spectroscopy and X-ray crystallography. The results show that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen atoms. The imido nitrogen and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre.

2-(5,6-Di-hydro-benzimidazolo[1,2-c]quinazolin-6-yl)aniline methanol solvate.

In the structure of the title compound, C20H16N4·CH4O, the aniline ring forms dihedral angles of 89.9 (2) and 85.4 (2)° with the benzimidazole and benzene rings, respectively. The orientation of the aniline ring is mainly determined by strong hydrogen bonds between the amino group and the non-fused quinazoline N atom. Intermolecular hydrogen bonds of the N—H⋯N—H⋯N type along [010] and the N—H⋯O—H⋯N type along [100] are formed, resulting in C 2 2(4) and C 2 2(10) descriptors, respectively, on a binary level of graph-set analysis. There are C—H⋯π contacts with H⋯π distances of 2.44 Å; however, no π-stacking is observed.

Oxidation of 5,6-Diamino-1,3-dimethyl-2,4-dioxopyrimidine by Perrhenate: the crystal structure of 1,3,6,8-Tetramethylpyrimidopteridine-2,4,5,7-tetrone

The oxidation of 5,6-diamino-1,3-dimethyl-2,4-dioxopyrimidine (H2ddd) by perrhenate (ReO4-) led to the formation of 1,3-dimethylalloxan, which condenses with unoxidized H2ddd to yield the product 1,3,6,8-tetramethylpyrimidopteridine-2,4,5,7-tetrone (tppt). The structure of tppt consists of a central pyrazine ring and two terminal pyrimidine rings in cis positions. The dihedral angles between the pyrazine and pyrimidine rings are 1.08° and 1.20°.

6-(2-Hydroxy­phen­yl)-5,6-dihydro­benzimidazolo[1,2-c]quinazolin-12-ium bromide ethanol solvate

In the title compound, C20H16N3O+·Br−·C2H6O, the phenol ring forms dihedral angles of 84.5 (1) and 89.3 (1)° with the benzimidazole system and the quinazoline benzene ring, respectively. The two N—H groups act as donors in hydrogen bonds with the bromide ion as acceptor, leading to infinite eight-membered chains along [100]. According to graph-set theory the descriptor on the binary level is C 2 1(8). O—H⋯O and O—H⋯Br hydrogen bonds also occur.

2,2′-Diamino-N,N′-(o-phenyl­ene)di­benz­amide

In the structure of the title compound, C20H18N4O2, the N—H and C=O bonds are trans to each other and the amide O atoms are syn to the ortho amino N atom in the benzoyl rings. The amide groups form dihedral angles of 8.4 (2) and 13.8 (2)° with their respective benzoyl rings, and dihedral angles of 51.85 (16) and 51.19 (17)° with the phenylenediamine ring. In the crystal, a centrosymmetric dimer is formed by intermolecular N—H⋯O hydrogen bonds, resulting in an R 2 2(14) descriptor on a unitary level of graph-set analysis, and three intramolecular N—H⋯O bonds also occur.