Chelating ligands ruthenium

Figure 1.29 Synthesis of ruthenium complexes of the chelating ligand bis(dimethylphosphino)-...

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

It appears that abpy- or abcp-substituted oxo-centered triruthenium derivatives exhibit a high stabilization on low-valence III,III,II and III,II,II species, which are usually unavailable through axial ligand substitution. The abpy or abcp exhibits a i-T 1(N),r 2(N,N) bonding mode, chelating one ruthenium center via azo N and pyridyl/pyrimidine N donors as well as bound to another ruthenium center via the other pyridyl/pyrimidine N donor. 

Ru(II)) excited ruthenium chelate, ligands omitted as well as in Ru(III). 

The use of an extended arene (tetrahydroanthracene) in [OsCl(en)(ri6-tha)]+ (29) gave rise to a similar potency (112). This is in contrast with the data for ruthenium-arenes, where the same substitution gave rise to a 10-fold increase in activity. Further work therefore needs to determine if the extended Os-arenes can intercalate into DNA in a manner similar to Ru-arenes. Replacement of the iV /V-chelating ligand en for other AyV-bidentates with pyridine, aliphatic amine, or azopyridine donor atoms leads to loss of activity, probably because of slower hydrolysis and higher acidity of the coordinated water (112). 

The complex [Ru(NO)(NH3)(S4)2] has been prepared and crystallographically characterized. It contains two 84 chelating ligands, and the NO and NH3 ligands are mutually trans. This complex was the first polysulfido nitrosyl complex of ruthenium. ... 

The majority of ruthenium(II) compounds which have been observed to be luminescent are complexes of aromatic heterocyclic chelating ligands. Methods of synthesizing such complexes are reviewed and recommendations made (where considered possible) as to the best procedures. 

Novel picolinate derivatives have been synthesised that show hydrolysis rates intermediate between the slow values for the complexes with /V,/V-chelating ligands, and the rapidly-hydrolysing complexes with 0,0- or N,0- amino acidlike chelating ligands. For these organometallic osmium complexes, the hydrolysis rates fall into the range of the active ruthenium-arene relatives (Fig.l) [66]. 

A fluorescent complex [Ru(r 6-p-cym)Cl(L)]Cl (L = 2-[(2-aminoethyl)amino] ethyl-2-(methylamino)benzoate) has been synthesised by tagging a small fluoro-genic reporter onto the chelating ligand. The interaction of this complex with porcine liver esterase (PLE) showed that esterase-catalysed hydrolysis reactions can liberate methylisatoic acid (MIAH) from the ruthenium complex suggesting a possible use of similar derivatives in esterase-activated Ru-based prodrug delivery systems. The hydrolysis reaction appears to be slow [156]. 

Habtemariam A, Melchart M, Fernandez R, Parsons S, Oswald IDH, Parkin A, Fabbiani FPA, Davidson JE, Dawson A, Aird RE, Jodrell DI, Sadler PJ (2006) Structure-activity relationships for cytotoxic ruthenium(II) arene complexes containing N, N-, N, O-, and O, O-chelating ligands. J Med Chem 49 6858-6868... 

Fernandez R, Melchart M, Habtemariam A, Parsons S, Sadler PJ (2004) Use of chelating ligands to tune the reactive site of half-sandwich ruthenium(II)-arene anticancer complexes. Chem Eur J 10 5173-5179... 

Zinc amalgam reduction of Ru(acac)3 in the presence of olefinic N- or O-donor chelating ligands affords the corresponding complexes 89 of ruthenium(II) . ... 

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