Triphenylmethyl Thionitrite: An Efficient NO Transfer Reagent During the Synthesis of a Triruthenium Nitrosyl Cluster

The synthesis and structural characterization of the novel triruthenium nitrosyl cluster [Ru-3(mu-NO)(CO)(5)(mu-H)(mu-PBu2t)(2)(mu-dppm)] (2) is described. Compound 2 was obtained by the reaction of the 46-valence electron cluster [Ru-3(mu-CO)(CO)(4)(mu(3)-H)(mu-H)(mu-PBu2t)(2)(mu-dppm)] (1) with nitric oxide and on the other hand in a more efficient way by the reaction of 1 with the nitrosyl transfer reagent triphenylmethyl thionitrite (TTN). The reaction of 1 with NO was outlined in dichloromethane whereas the reaction with TTN was realized in THF. Both methods worked at ambient temperature affording compound 2 in high yield. Temporarily we found that the transformation of 1 with NO was accompanied by a fast side-reaction resulting in a further substitution of CO ligands. The molecular structure of 2 in the crystal was confirmed by single-crystal X-ray diffraction

Reactivity of Cyanide and Thiocyanate Towards the Nitrosyl Carbonyl [Co(CO)3(NO)]

The reaction of equimolar amounts of [Co(CO)3(NO)] and [PPN]CN, PPN+ = (PPh3)2N+, in THF at room temperature resulted in ligand substitution of a carbonyl towards the cyanido ligand presumably affording the complex salt PPN[Co(CO)2(NO)(CN)] as a reactive intermediate species which could not be isolated. Applying the synthetic protocol using the nitrosyl carbonyl in excess, the title reaction afforded unexpectedly the novel complex salt PPN[Co2(μ‐CN)(CO)4(NO)2] (1) in high yield. Because of many disorder phenomena in crystals of 1 the corresponding NBu4+ salt of 1 has been prepared and the molecular structure of the dinuclear metal core in NnBu4[Co2(μ‐CN)(CO)4(NO)2] (2) was determined by X‐ray crystal diffraction in a more satisfactory manner. In contrast to the former result, the reaction of [PPN]SCN with [Co(CO)3(NO)] yielded the mononuclear complex salt PPN[Co(CO)2(NO)(SCN‐κN)] (3) in good yield whose molecular structure in the solid was even determined and its composition additionally confirmed by spectroscopic means

Spontaneous Reductive Elimination at Iridium(III) Induced by the Strong π‐Acceptor Ligand Trifluorophosphane

The reaction of the cyclometalated five‐coordinate 16 VE iridium(III) compound [IrCl(H)(P(tBu)2C6H4‐κ2P,C)(P(tBu)2Ph)] (1) with the strong π‐acceptor ligand trifluorophosphane resulted quickly in the quantitative formation of the new iridium(I) complex trans‐[IrCl(PF3)(P(tBu)2Ph)2] (2). This unexpected spontaneous reductive elimination was already observed in reactions of 1 with the very strong π‐acceptor ligands CO and NO+. First indications during reactions of 1 with lesser strong π‐acceptor ligands like alkyl or arylphosphanes did not show this inversion behavior of the cyclometalation. The title species 2 was characterized by spectroscopic methods and its molecular structure in the crystal was confirmed by X‐ray crystallography

Coinage Metal Complexes of Bis(quinoline-2-ylmethyl)phenylphosphine-Simple Reactions Can Lead to Unprecedented Results

The different coordination behavior of the flexible yet sterically demanding, hemilabile P,N ligand bis(quinoline-2-ylmethyl)phenylphosphine (bqmpp) towards selected Cu-I, Ag-I and Au-I species is described. The resulting X-ray crystal structures reveal interesting coordination geometries. With [Cu(MeCN)(4)]BF4, compound 1 [Cu-2(bqmpp)(2)](BF4)(2) is obtained, wherein the copper(I) atoms display a distorted square planar and square pyramidal geometry. The steric demand and pi-stacking of the ligand allow for a short Cu...Cu distance (2.588(9) angstrom). Cu-I complex 2 [Cu4Cl3(bqmpp)(2)]BF4 contains a rarely observed Cu4Cl3 cluster, probably enabled by dichloromethane as the chloride source. In the cluster, even shorter Cu...Cu distances (2.447(1) angstrom) are present. The reaction of Ag[SbF6] with the ligand leads to a dinuclear compound (3) in solution as confirmed by P-31{H-1} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3, a tris(quinoline-2-ylmethyl)bisphenyl-phosphine (tqmbp) compound [Ag-2(tqmbp)(2)](SbF6)(2) 4 is formed by elimination of quinaldine. The Au(I) compound [Au-2(bqmpp)(2)]PF6 (5) is prepared as expected and shows a linear arrangement of two phosphine ligands around Au-I

Cytotoxic Activities of Half‐sandwich M(III) Complexes (M=Rh, Ir) Bearing Chloro‐substituted Bidentate‐coordinated Phenanthroline or Terpyridine Ligands

The synthesis and characterization of four compounds [M(η5-C5Me5)(N^N)Cl]PF6 [N^N=4,7-dichloro-1,10-phenanthroline with M=Rh, 1, and M=Ir, 2, and N^N=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine in the κ2N,N'-coordination mode with M=Rh, 3, and M=Ir, 4] are described. All compounds were characterized by spectroscopic means and their molecular structures in the crystal were confirmed by single-crystal X-ray diffraction studies. The cytotoxicity of all compounds was evaluated by MTT assay against the three cancer cell lines HeLa (cervical carcinoma), HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma). The complexes 3 and 4 display promising activity with IC50 values of 1 μM. The rhodium(III) complex 1 also shows highly improved cytotoxicity compared to cisplatin against the cancer cell lines HT-29 and MCF-7. In contrast to this, the iridium(III) complex 2 is even less active against the HeLa cell line than cisplatin

Cytotoxic Activities of Bis-cyclometalated M(III) Complexes (M=Rh, Ir) Containing 5-substituted 1,10-Phenanthroline or 4,4'-substituted 2,2'-Bipyridine Ligands

The synthesis and characterization of eight new bis-cyclometalated compounds [M(ptpy)(2)(NN)]PF6 (ptpy=2-(p-tolyl)pyridinato;NN=5-chloro-1,10-phenanthroline: M=Rh, 1;M=Ir, 2);NN=5-methyl-1,10-phenanthroline: M=Rh, 3;M=Ir, 4;NN=4,4'-diphenyl-2,2'-bipyridine: M=Rh, 5;M=Ir, 6;NN=4,4'-diamino-2,2'-bipyridine: M=Rh, 7;M=Ir, 8) are described. All compounds were characterized by spectroscopic means. Additionally, the molecular structures of compounds 4, 5, 6, and 8 in the crystal were determined by single-crystal X-ray diffraction studies. To explore the cytotoxic properties of all new eight compounds, colorimetric assays (MTT assay) against prominent cancer cell lines, MCF-7 and HT-29, were performed. The determined IC50 values are in the low micromolar range, between 1.3-5.6 mu M. The most effective compounds are 1 and 2 with 5-chloro-substituted phenanthroline ligands, whereas the diamino-substituted bipyridine ligands (5 and 6) are the least cytotoxic compounds. The tested complexes showed a significant increase in cytotoxicity, up to 25-fold increase in MCF-7 cancer cells, and up to 60-fold increase in the HT-29 cell line compared to the established anticancer compound cisplatin under identical conditions

Cytotoxic Activity of Some Half‐sandwich Rhodium(III) Complexes Containing 4,4’‐disubstituted‐2,2’‐bipyridine Ligands

The synthesis and characterization of three compounds [Rh(η5-C5Me5)Cl(N^N)]PF6 (N^N=4,4’-disubstituted-2,2’-bipyridines, 1–3) are described. The cationic complexes contain the bidentate ligands N^N=4,4'-di-tert-butyl-2,2'-bipyridine (1), N^N=4,4'-dinonyl-2,2'-bipyridine (2) and N^N=4,4'-diamino-2,2'-bipyridine (3). The complex salts were obtained by the bridge-splitting reaction from the precursor [{Rh(η5-C5Me5)(μ-Cl)Cl}2] and subsequent salt metathesis affording their corresponding hexafluorido phosphate salts. All compounds were characterized by elemental analysis and spectroscopic means. Additionally, the molecular structure of compound 3 in the solid was determined by a single-crystal X-ray diffraction study. The cytotoxicity of all three compounds was examined by MTT assay against two cancer cell lines – HT-29 (colon adenocarcinoma) and MCF-7 (human breast adenocarcinoma) - and normal human fibroblast cells (GM5657T). Compound 1 has moderate cytotoxicity against both cell lines, while compound 2 is seven to nine times more cytotoxic than cisplatin against MCF-7 and HT-29, respectively. In contrast to cisplatin, both compounds are more active against cancer cells than fibroblasts, thus showing some cancer selectivity

Cytotoxic Activities of Bis-cyclometalated Iridium(III) Complexes Containing Chloro-substituted kappa N-2-terpyridines

The synthesis and characterization of two new bis-cyclometalated compounds [Ir(ptpy)(2)(kappa N-2-terpy-C6H4Cl-p)]PF6 [terpy-C6H4Cl-p=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine, (1)], and [Ir(ptpy)(2)(kappa N-2-terpy-Cl)]PF6 [terpy-Cl=4'-chloro-2,2':6',2''-terpyridine, (2);ptpy=2-(p-tolyl)pyridinato)] are described. The molecular structures of compounds 1 and 2 in the crystal were determined by single-crystal X-ray diffraction. 1 crystallized from dichloromethane/methanol/iso-hexane in the monoclinic space group P2/(n) and 2 from the same mixture of solvents in the triclinic space group P(-)1. Photophysical investigations on 1 and 2 revealed broad unstructured luminescence in the red spectral region with the emission maxima in dichloromethane at 620 and 630 nm respectively. To explore cytotoxic properties of compounds 1 and 2, a colorimetric assay (MTT assay) against prominent cancer cell lines, MCF-7 and HT-29, was performed. The determined IC50 values are in the low micromolar range (2-3 mu M). In comparison to cisplatin, the tested complexes 1 and 2 exhibit up to >20-fold (MCF-7) and >40-fold (HT-29) increase in biological activity

Cytotoxic Activities of Bis‐cyclometalated Rhodium(III) and Iridium(III) Complexes Containing 2,2’‐Biphenyldiamine

The synthesis and characterization of new bis-cyclometalated complex salts [M(ptpy)(2)(2,2'-biphenyldiamine)]PF6 (M=Rh, 1; M=Ir, 2; ptpy=2-(p-tolyl)pyridinato) are described. Compounds 1 and 2 were obtained by bridge-splitting reactions of [{M(mu-Cl)(ptpy)(2)}(2)] (M=Rh or Ir) with 2,2'-biphenyldiamine in CH2Cl2/MeOH/H2O mixtures. The molecular structure of compound 2 in the crystal was confirmed by single-crystal X-ray diffraction. 2 crystallized from dichloromethane/methanol/n-heptane in the monoclinic space group P2(1)/(n). The cytotoxic activities of both new compounds were examined and evaluated. Compound 1 and 2 exhibit significant cytotoxicity against human cancer cell lines with the IC50 values in the low micromolar range

Cytotoxic Activities of Bis‐cyclometalated Iridium(III) Complexes Containing Chloro‐substituted κ2N‐terpyridines

The synthesis and characterization of two new bis-cyclometalated compounds [Ir(ptpy)(2)(kappa N-2-terpy-C6H4Cl-p)]PF6 [terpy-C6H4Cl-p=4'-(4-chlorophenyl)-2,2':6',2''-terpyridine, (1)], and [Ir(ptpy)(2)(kappa N-2-terpy-Cl)]PF6 [terpy-Cl=4'-chloro-2,2':6',2''-terpyridine, (2); ptpy=2-(p-tolyl)pyridinato)] are described. The molecular structures of compounds 1 and 2 in the crystal were determined by single-crystal X-ray diffraction. 1 crystallized from dichloromethane/methanol/iso-hexane in the monoclinic space group P2/(n) and 2 from the same mixture of solvents in the triclinic space group P(-)1. Photophysical investigations on 1 and 2 revealed broad unstructured luminescence in the red spectral region with the emission maxima in dichloromethane at 620 and 630 nm respectively. To explore cytotoxic properties of compounds 1 and 2, a colorimetric assay (MTT assay) against prominent cancer cell lines, MCF-7 and HT-29, was performed. The determined IC50 values are in the low micromolar range (2-3 mu M). In comparison to cisplatin, the tested complexes 1 and 2 exhibit up to >20-fold (MCF-7) and >40-fold (HT-29) increase in biological activity