A di-palladium urea complex as a molecular receptor for anions

N,N′-Dimethylurea as an efficient ligand for the synthesis of pharma-relevant motifs through Chan–Lam cross-coupling strategy

The combination of copper and N,N′-dimethylurea is used to showcase the Chan–Lam N-arylation of three different nitrogen nucleophiles. The synthesized catalyst is cheap, chemoselective, and also found to be effective in the N-arylation of target APIs.

Mixed NHC-thiolato complexes of palladium: understanding the formation of di-versus mononuclear complexes

The preference for the formation of mono- versus dinuclear mixed carbene/thiolato complexes of Pd^II has been studied with three types of N-heterocyclic carbenes derived from benzimidazole, imidazole and 1,2,4-triazole. The complexes were prepared by treatment of halido/NHC precursors with sodium isopropylthiolate in a salt metathesis reaction. Mononuclear complexes are formed when the sulfur and carbon donors are exclusively cis to each other, while their trans arrangement preferably leads to dinuclear complexes with μ₂-bridging thiolato ligands. The increased electron density in the latter case cannot be sufficiently compensated by one Pd^II center alone and leads to the formation dinuclear species with bridging thiolato ligands.

Sulfonamide carbazole receptors for anion recognition

Carbazole-based receptors functionalized with two sulfonamide groups have been synthesized and their properties as anion receptors have been evaluated. The receptor with bis(trifluoromethyl)aniline groups has shown a very high affinity for halide ions, especially remarkable as only two hydrogen bonds are formed in the complexes. (1)H NMR and fluorescence titrations have been carried out and binding constants up to 7.9 × 10(6) M(-1) have been reached. X-ray structures have been obtained and a modelling study has shown the possible reasons for the large affinity of these compounds for halide anions.

Enhanced anion binding from unusual coordination modes of bis(thiourea) ligands in platinum group metal complexes

Treatment of a range of bis(thiourea) ligands with inert organometallic transition-metal ions gives a number of novel complexes that exhibit unusual ligand binding modes and significantly enhanced anion binding ability. The ruthenium(II) complex [Ru(η(6)-p-cymene)(κS,S',N-L(3)-H)](+) (2b) possesses juxtaposed four- and seven-membered chelate rings and binds anions as both 1:1 and 2:1 host guest complexes. The pyridyl bis(thiourea) complex [Ru(η(6)-p-cymeme)(κS,S',N(py)-L(4))](2+) (4) binds anions in both 1:1 and 1:2 species, whereas the free ligand is ineffective because of intramolecular NH⋅⋅⋅N hydrogen bonding. Novel palladium(II) complexes with nine- and ten-membered chelate rings are also reported.

On the many roles of NH3 ligands in mono- and multinuclear complexes of platinum

The role of the NH(3) ligands in the highly successful antitumour agents cisplatin and carboplatin is not fully understood. Suggestions that the ammonia ligands are involved in target recognition through hydrogen bond formation, e.g. with guanine-O6, have been questioned. Here, we review the roles and functions of NH(3) ligands of cis-PtCl(2)(NH(3))(2) and likewise of its trans-isomer in complexes with model nucleobases as well as other N-heterocyclic ligands. Specifically, their roles in hydrogen bonding interactions with nucleobases as well as anions, the influence on acid-base properties of co-ligands, their involvement in condensation reactions, as well as a variety of displacement reactions will be examined. As a result, it can be stated that the ammonia ligands in cis- and trans-Pt(II)(NH(3))(2) entities display additional features to those generally discussed in the last four decades since the discovery of the antitumour activity of cisplatin.

Di-platinum complexes containing thiolato-urea ligands: structural and anion binding studies

The new di-platinum(II) thiolato-bridged complexes [(dppp)Pt{micro-S(CH(2))(n)NHC([double bond, length as m-dash]O)NHR}](2)(OTf)(2) (n = 2, 3; R = Et, Ph) have been synthesized. The X-ray crystal structures of three of these complexes have confirmed their formulation and highlighted the ability of the urea groups on the thiolato bridges to display hydrogen bonding interactions with anions. The binding of anions by these receptors has been quantitatively determined by (1)H NMR spectroscopy and in a qualitative fashion by indicator displacement assays. These studies have shown the receptors to be selective for inorganic phosphate. In addition we have isolated and structurally characterized an unusual 1D coordination polymer with formula {[(dppp)Pt{micro-S(CH(2))(2)NHC([double bond, length as m-dash]O)NHR}][Pb(2)Cl(6)]}(n). The X-ray crystal structure of this inorganic polymer has shown that it consists of units of the di-platinum-thiolato cations bridged by [Pb(2)Cl(6)](2-) moieties.

Pressure-Assisted Hetero- and Homodialkylation of Sulfide in [Pt2(μ-S)2(dppp)2]: One-Pot Conversion of {Pt2(μ-S)2} into {Pt2(SR)2} and {Pt2(SR)(SR′)}

Heterodialkylation of [Pt2(mu-S)2(dppp)2] (dppp = Ph2P(CH2)3PPh2) was achieved under high pressure (10 kbar). This enabled the synthesis of rare diplatinum complexes with structurally diverse thiolate bridges, such as [Pt2(mu-SC5H10CO2CH2CH3)(mu-SC3H7)-(dppp)2](PF6)2, which was crystallographically identified. Complete homodialkylation was also achieved under similar conditions (6 kbar at room temperature), thus permitting the isolation of [Pt2(mu-SC2H4CO2CH2CH3)2(dppp)2]-(PF6)2. The isolation of these complexes extends the applications of high-pressure chemistry to thiolato homo- and heterobridged complexes that are otherwise not accessible.