Ruthenium complexes biphenyl

P-Cyclodextrines, appended to a ruthenium complex, have been employed as hosts for iridium and osmium complexes bearing adamantyl or biphenyl moieties, which form strong host-guest complexes with P-cyclodextrines (see Fig. 3). In such systems, photoinduced energy transfer can occur from the periphery, upon complexation of the iridium units, toward the central ruthenium acceptor, or switched in the other direction, from the ruthenium to the periphery when the osmium moieties are assembled (see Fig. 3) 42). The lowest excited state is in fact localized on the osmium center, while the highest luminescent excited state belongs to the iridium complex (see Fig. 3 right). 

A versatile route to 3-benzoheteropines has been reported starting from o-phthalaldehyde, including the first preparations of 3-benzarsepines and the parent 3-benzothiepin and 3-benzoselenepins <96CC2183>. l,7-Dihydro-l//-dibenzo[c,c]tellurepin has been prepared from 2,2 -bis(bromomethyl)biphenyl and potassium tellurocyanate and its complexes with palladium and ruthenium species have been studied, a number of mono- and binuclear complexes are formed <96RTC427>. 

Janetka and Rich (78) have utilized the considerable stability of ruthenium-77-arene systems in the synthesis of cyclic tripeptides as analogs of the protease inhibitor K-13 (cf. 34, Scheme 28). Their approach involves the construction of linear tripeptide complexes (35) using diimide/HOBt coupling of [Ru(Cp)(Boc-p-Cl-PheOH)]PF6 (Cp = 775-C5H5) with the appropriate dipeptide ester. Cyclization of 35 affords the biphenyl ether 36, which on photolysis (350 nm) gives 34. 

Tethered arene complexes of ruthenium(II) are also formed readily when the conformational freedom of the tether is restricted, for which purpose the biphenyl unit has proved ideal. Thus, (2-dicyclohexylphosphino)biphenyl and its derivatives react with [RuCl2(r 6-C6H6)]2 in DMF at 100 °C to give directly the tethered complexes 67-69 in yields of 31-96% without detection or isolation of the presumed P-coordinated intermediates.65... 

Chiral silver complexes bearing bidentate NHC ligands (24) have been synthesized. They are used in alkene metathesis and allylic alkylation reactions high diastereos- (g) electivity is observed induced by the chiral backbone on the prochiral biphenyl.27 Ruthenium-based complexes obtained from transmetalation with a Grubbs-Hoveyda complex exhibited high activities and enantioselectivities in ring-opening metathesis/ ... 

Consequently, organometallic ruthenium(II) and osmium(II) arene complexes have recently attracted interest as anticancer agents [51]. The presence of a 7i-bonded arene in Ru11 (and Os11) complexes can have a dramatic influence on their chemical reactivity. There is a delicate balance between electron donation from the arene into the empty Ru 4d orbitals and back-donation from the filled 4d6 orbitals into vacant arene orbitals. This is influenced by the donor-acceptor power of the arene (e.g. hexamethylbenzene as a strong donor, in contrast to biphenyl which may act as acceptor) and by the other ligands on Ru11 which can influence the... 

The simpler architecture is the 1,1 -biphenyl scaffold, likewise introduced by Hoveyda and coworkers [19]. The synthesis of the imidazolium salt starts with a chiral diamine and a substituted, achiral biphenyl [82-84], Subsequent introduction of a Mes substituent on the remaining primary amino end and ring closure reaction yields the chiral saturated imidazolium salt after hydrolysation of the methoxy group to liberate the phenolic hydroxy group (see Figure 4.22). Reaction with silver(I) oxide and carbene transfer to a Grubbs (Hoveyda) catalyst sets up the ruthenium catalyst complex. 

Biphenyl is reductively eliminated from a ruthenium diphenyl complex by simply heating the diaryl compound at 85°C. The ruthenium intermediate involved in the reductive elimination can be trapped with phosphine in quantitative yield . 

Ruthenium arenes are another interesting class of organometallics with proven anticancer activity. The most active complex [( 7 -biphenyl)Ru(ethylene-diamine)Cl] 1 (Scheme 11) had an activity comparable to Garboplatin against a human ovarian cancer cell line. " The interaction of this compound with different biomolecules has been studied, and again, DNA has been suggested as the primary target. It is, however, unclear at present... 

Ruthenium arene complexes appear to have a wide spectrum of cytotoxicity towards cancer cells. For example, the complexes [(ri -biphenyl)Ru(en)Cl]PFg and [(ri -dihydroanthracene)Ru(en)Cl)PF 5 are active against not only AZ7S0 human ovarian cancer cells, but also HT29 colon, Panc-1 pancreatic and NX02 lung cancer cells with IC5Q values in the range 1-13 pM [77]. 

Blechert et al. successfully introduced a desymmetrization approach. An asymmetric ring-opening cross metathesis of norbornenedicarboxylic anhydride was rendered possible by a Hoveyda- Blechert type ruthenium- carbene complex with a chiral N-heterocyclic carbene (NHC) ligand (Scheme 5.6). The chiral iirforma-tion of the NHC backbone was translated into ruthenium s active coordination sphere by the steric repulsion of an isopropyl group with a skewed ort/ro-biphenyl substituent [17]. 

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