1,4-Bis(4-nitrosophenyl)piperazine: novel bridging ligand in dinuclear complexes of rhodium(iii) and iridium(iii)

Abstract

The synthesis, spectroscopic characterization and crystal structures of the first 1,4-bis(4-nitrosophenyl)-piperazine (BNPP) (4) bridged dinuclear complexes of rhodium(III) and iridium(III) are presented. All new compounds were characterized by their NMR, IR and mass spectra. The X-ray structure analyses of the obtained half-sandwich complexes revealed a slightly distorted pseudo-octahedral configuration ("three-legged pianostool") for the metal(III) centers. The bridging BNPP ligand is s-N coordinated by both nitroso groups and shows different conformations of the piperazine ring depending on the solvent used for crystallization. Moreover the crystal structures of 1,4-bis(4-nitrosophenyl)piperazine (4) and its precursor 1,4-diphenylpiperazine (3) are reported.

Reactivity of 4-Nitrosoanilines Towards Dimeric Halogenido-bridged Complexes of Iridium(III) and Rhodium(III) of the Type [(η5- C5Me5)MX2]2

“…Structure determinations are only known for ligand 3 (Rh-N 2.050(4)Å) [32] or 1-bromo-4-nitrosobenzene (Rh-N 1.958(3)Å) [30] at Rh(I) centers. Again the Rh-N bond lengths observed in 7a (2.1069(18)Å) and 8a (2.086(3)Å) are slightly longer and in good accordance to our results for 1,4-bis(4-nitrosophenyl)piperazin (2.097(2)Å) [36]. Thus, the M-N bond lengths found in 5a-8a are close to those observed in Rh(III) or Ir(III) complexes with bidentate sp 2 -N-donor ligands [53 -57].…”

“…(Table 2; only exception 7a: N2-M-X2) and prove the only slight distortion of the pseudo-octahedral geometry. The Ir-N bonds observed in 5a, 5c and 6a-c are in the range 2.054(2)-2.087(3)Å and therefore somewhat longer than reported for 1-chloro-2-nitroso-1,2-dihydrodicyclopentadiene σ -N coordinated to Ir(III) (1.948(6)Å) [52], but similar to that of our own recently published dinuclear Ir(III) complexes (2.061(4)-2.088(3)Å) [36]. Crystallographic data for C-nitroso ligands with σ -N coordination to Rh(III) are not available from other groups.…”

“…Besides our own results [36], the available crystallographic data for monodentate σ -N-coordination is limited to only two Rh(I) complexes [30,32]. In fact, the new complexes presented in the following are the results of preliminary research to our recently published work on 1,4-bis(4-nitrosophenyl)piperazine as a bridging ligand [36] and are the only further examples for crystallographically characterized Ir(III) and Rh(III) complexes containing monodentate σ -N-coordinated aromatic C-nitroso ligands. c 2012 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com Scheme 1.…”

A structural study of 2,4-dimethylaniline derivatives

“…In the case of the more sterically hindered derivative 1, this arrangement is not feasible and chains are instead adopted. Most of the crystallographically characterized diarylpiperazines feature the chair conformation; a few have been determined in the twist-boat form (Wirth et al, 2012). Whereas the phenyl groups of piperazine 2 are twisted relative to the N 2 C 4 mean plane, the structure of the less substituted N,N 0 -diphenylpiperazine, which crystallizes in the Pbca space group, exhibits phenyl groups closer to being in conjugation with the nitrogen lone pairs (Wirth et al, 2012;Safko & Pike, 2012).…”

Enhanced Sensing of 4-Nitroso-N,N–Dimethyl Aniline using Multi-Walled Carbon Nano Tube Modified Glassy Carbon Electrode

“…These compounds were also used in the synthesis of some natural product building blocks with high enantiomeric purity [10]. On the other hand, the presence of two heteroatoms (oxygen and nitrogen) in the nitroso group makes these compounds suitable as ligands for the synthesis of a wide variety of metal complexes [11]. From the medical point of view, N-Nitroso compounds are known to be potent animal carcinogens [12].These compounds react in biological systems with biomolecules that have sulfur atoms such as proteins with cysteine residues or glutathione, as potential nucleophiles [13].…”