Arene displacement, C-H activation and acetonitrile insertion reactions enabled by coordination of a functionalized iminophosphorane to a RuII-p-cymene scaffold

Reaction of a sterically demanding iminophosphorano-phosphine, Ph2PCH2Ph2PNAr* (here onwards referred to as PCPNAr*; Ar* = 2,6-dibenzhydryl-4-methylphenyl), (1) with [Ru(η6-p-cymene)Cl2]2 yielded three different types of complex, [RuCl2{(η6-p-cymene)(PCPNAr*)-κ1-P}] (2), [RuCl{(P(O)CPNAr*)(κ2-N,C)(C-η6-arene)}] (3) and [RuCl{(POCPNAr*)(κ2-N,C-o)(C-η6-arene)}] (4), depending on the reaction conditions via CH activation, tethered η6-arene coordination, ortho-metallation or PN bond cleavage/rearrangement reactions. Interestingly, a similar reaction in CH3CN in the presence of AgBF4 resulted in the insertion of CH3CN into the PN bond to form a novel metallacycle [Ru(NCMe)3{(PC2PN(CH3)CNAr*)-κ3-N,N,P}][BF4]2 (5) containing 4- and 5-membered rings via an aza-Wittig type reaction. Complex 4 showed very good catalytic activity in the transfer hydrogenation of carbonyl compounds.

Heteroleptic mononuclear compounds of ruthenium(ii): synthesis, structural analyses, in vitro antitumor activity and in vivo toxicity on zebrafish embryos

The limitations of platinum complexes in cancer treatment have motivated the extensive investigation into other metal complexes such as ruthenium. We herein present the synthesis and characterization of a new family of ruthenium compounds 1a-5a with the general formula [Ru(bipy)₂L][CF₃SO₃]₂ (bipy = 2,2'-bipyridine; L = bidentate ligand: N,N; N,P; P,P; P,As) which have been characterized by elemental analysis, ES-MS, ¹H and ³¹P-{¹H} NMR, FTIR and conductivity measurements. The molecular structures of four Ru(ii) complexes were determined by single crystal X-ray diffraction. All compounds displayed moderate cytotoxic activity in vitro against human A2780 ovarian, MCF7 breast and HCT116 colorectal tumor cells. Compound 5a was the most cytotoxic compound against A2780 and MCF7 tumor cells with an IC₅₀ of 4.75 ± 2.82 μM and 20.02 ± 1.46 μM, respectively. The compounds showed no cytotoxic effect on normal human primary fibroblasts but rather considerable selectivity for A2780, MCF7 and HCT116 tumor cells. All compounds induce apoptosis and autophagy in A2780 ovarian carcinoma cells and some nuclear DNA fragmentation. All compounds interact with CT-DNA with intrinsic binding constants in the order 1a > 4a > 2a > 3a > 5a. The observed hyperchromic effect may be due to the electrostatic interaction between positively charged cations and the negatively charged phosphate backbone at the periphery of the double helix-CT-DNA. Interestingly, compound 1a shows a concentration dependent DNA double strand cleavage. In addition in vivo toxicity has been evaluated on zebrafish embryos unveiling the differential toxicity between the compounds, with LC₅₀ ranging from 8.67 mg L^-1 for compound 1a to 170.30 mg L^-1 for compound 2a.

Palladium complexes derived from N,N-bidentate NH-iminophosphorane ligands: synthesis and use as catalysts in the Sonogashira reaction

The addition of primary amines to the C=C bond of diphenylalkenyl iminophosphoranes yielded a new subtype of N,N-bidentate ligands bearing N=P(V)-C-C-NH backbones. These donor ligands reacted with PdCl(2)(COD) to give the corresponding σN,σN-palladium complexes containing secondary amino groups, bearing an intrinsically chiral nitrogen atom, and iminophosphorane units. These new complexes have been fully characterized by the use of spectroscopic techniques and X-ray crystallography. The comparison of the data extracted from their solution NMR spectra with their solid state structures demonstrated the conformational stability of their six-membered chelate ring and also the configurational stability of the chiral nitrogen atom, thus ruling out an arm-off racemization process. The addition of the chiral, racemic α-methylbenzylamine to the prochiral P-alkenyl iminophosphoranes yielded mixtures of the two expected diasteroisomeric ligands in low diastereoisomeric ratios. One of these mixtures was resolved into their components, each one in turn giving rise to a pair of diasteromeric palladium complexes epimeric at the amino nitrogen atom. One selected example of the new complexes efficiently catalyzes the copper- and amine-free Sonogashira reaction of aryl halides with acetylenes.

Luminescent ruthenium-polypyridine complexes & phosphorus ligands: anything but a simple story

This tutorial review presents an exhaustive picture of the luminescence studies that have been undertaken on ruthenium(ii) complexes bearing polypyridine and phosphorus(iii) ligands. The introduction of phosphorus to the Ru coordination sphere has multiple consequences on the nature and energy of the various excited states involved, but it does not necessarily rule out room temperature emission.