Search

In an attempt to understand the factors that govern the rates of reaction of the complexes [Pt(en)Cl(NH2R)]+NO3− (en = ethylene diamine) with guanosine monophosphate (dGMP) a series of amine complexes, where R＝C8H9NO2 (benzo[d][1,3]dioxol-5-ylmethanamine) (1), C8H11N (phenethylamine) (2), C7H9N (benzylamine) (3), C6H7N (aniline) (4), C6H6IN (p-iodo-aniline) (5) C3H9NO (2-methoxy-ethylamine) (6) and C6H13N (cyclohexylamine) (7), were synthesized and their reactions with deoxyguanosine monophosphate (dGMP) were followed by 1H NMR. Compound 1 was initially chosen because it showed significant water solubility. Compound 1 reacted quantitatively but slowly with dGMP and a subsequent Transmission Electron Microscopy (TEM) study of the binding 1 to a GATC DNA repeat gave a TEM micrograph that showed selective labeling of DNA at guanine, using a technique that allowed the laying down of a straight single strand of DNA on a carbon platform. The TEM suggested a possible side reaction with adenine and so a study of the reaction of 1 with adenine was performed and showed slow and what appeared to be non-specific binding to deoxyadenosine monophosphate (dAMP). The reactions of compounds 2–7 with dGMP were then studied by 1H NMR and it was found that 2 reacted much faster than 1 with dGMP while the remaining complexes reacted more slowly. No reaction of 2 with dAMP was observed in the same time frame. The ultimate goal of the project was to bind a third row transition metal cluster to guanine and given the effective binding of 1 to DNA the synthesis of the complex [Os3(CO)11PPh2(CH2)2NH2(en)PtCl]NO3 (9) is also reported that contains Pt as a linker to label guanine. The synthesis was performed by reacting Os3(CO)10(CH3CN)2 with Ph2PCH2CH2NH2 which gave an η2 chelate complex Os3(CO)10PPh2(CH2)2NH2 (8). Complex 8 was reacted with [Pt(en)Cl(DMF)]NO3 in a CO atmosphere to give 9. 1H and 195Pt NMR indicate formation of an adduct with dGMP but too slowly to be of use in labeling DNA. The solid-state structure of 8 is also reported. [Copyright &y& Elsevier]

Abstract: Coordination of CoCl2 solutions to the silica polyamine composite, WP-1, made with the branched polymer polyethylenimine (PEI) shows irreversible binding resulting from surface oxidation of the Co2+–Co3+. This is not the case for the silica polyamine composite BP-1 made with the linear polymer polyallylamine where reversible binding and no oxidation is observed. These observations suggested that oxidation of the cobalt was related to the greater coordination number available with the branched polyamine relative to the linear polyamine. A study of the kinetics of cobalt binding to WP-1 indicated initial loading of Co2+ at relatively low coordination number followed by desorption of Co2+ leading to oxidation and irreversible binding. Exclusion of oxygen from the composite-cobalt solution mixtures resulted in irreversible binding at a level that was 14% of the initial experiments. These observations prompted us to undertake a study to elucidate the coordination number around cobalt in the case of the branched polymer PEI. Towards this end, we have synthesized the model complexes [(tren)Co(H2O)2]3+3Cl− (tren=tris(2,2′,2″aminoethyl)amine) and [(dien)Co(H2O)3]3+3Cl− (dien=diethylenetriamine). The UV–Vis spectra of these model complexes were compared with Co3+ coordinated to PEI in solution and it was concluded that the UV–Vis spectrum of the tren complex was closer to that observed for the solution UV–Vis spectrum of Co3+–PEI. These data indicated that coordination of four amines was needed to drive surface oxidation under ambient conditions. In order to further elucidate the coordination number of a metal coordinated to the surfaces of WP-1 and BP-1, we reacted these composites with the probe molecule [Ru(CO)3(TFA)3]−K+ (TFA=trifluoroacetate) (1) where the carbonyl stretching frequencies could be used as a measure of coordination number and geometry of the adsorbed complex. The IR of this complex on WP-1 indicated a monocarbonyl species while the IR of this complex on BP-1 indicated the presence of dicarbonyl species on the surface. These data are consistent with a coordination number of four amines in the case of WP-1 and the coordination of two amines in the case of BP-1 based on our previous studies of the solution coordination chemistry of the 1. Subsequent 13C CPMAS solid-state NMR on 13CO enriched samples of the 1 adsorbed onto BP-1 and WP-1 were consistent with the IR data. [Copyright &y& Elsevier]

The reactions of the electron deficient benzoheterocycle clusters Os3(CO)9(μ3-η2-L&z.sbnd;H)(μ-H) (L=phenanthridine, 2; 5,6-benzoquinoline, 3; quinoxaline, 4; 2-methyl benzimidazole, 5; 2-methyl benzotriazole, 6; 2-methyl benzothiazole, 7; benzothiazole, 8; 2-methyl benzoxazole, 9; benzoxazole, 10) with n-butylamine and with the protic acids HBF4 and CF3CO2H are reported. Complexes 2 and 3 behave very similarly to the analogous quinoline complex (L=quinoline, 1) forming adducts with n-butylamine with similar spectral properties to 1 and undergoing simple protonation at the metal core with both HBF4 and CF3CO2H. Complexes 4–10 on the other hand form an additional amine adduct with different spectral characteristics than 1–3 and in the case of 5 this is the only detectable product. In addition, these compounds also form adducts with acetonitrile while 1–3 do not. Compounds 4–9 also exhibit much more complex behavior in the presence of CF3CO2H than 1–3, giving trifluoroacetate adducts subsequent to initial protonation. Although 4, 5 and 10 behave differently than 1 with n-butylamine and protic acids they form exactly the same triphenyl phosphine adduct as 1 and 3 based on multinuclear NMR data. The solid-state structure for the amine adduct of 2 is reported and suggested structures for the other amine and acid adducts, based on NMR data, are presented. The reasons for the differences in the behavior of the three distinct groups of benzoheterocycles (1–3, 4 and 5–10) are discussed. [Copyright &y& Elsevier]

[Display omitted] Reactions of the electron defficient triosmium [Os 3 (CO) 9 (μ 3 -η1,κ1-C 9 H 6 N)(μ-H)] with Ph 3 EH (E = Si, Ge, Sn) have been investigated. The reactions of quinoline-capped triosmium cluster [Os 3 (CO) 9 (μ 3 -η1,κ1-C 9 H 6 N)(μ-H)] (1) with Ph 3 EH (E = Si, Ge, Sn) have been investigated. Cluster 1 reacts with Ph 3 EH in refluxing benzene to afford [Os 3 (CO) 9 (EPh 3)(μ-η1,κ1-C 9 H 6 N)(µ-H) 2 ] (2a , E = Si; 2b , E = Ge; 2c , E = Sn) and [Os 3 (CO) 8 (EPh 3)(μ 3 -η1,κ1-C 9 H 6 N)(µ-H) 2 ] (3a , E = Si; 3b , E = Ge; 3c , E = Sn). Control experiments confirm that 2 is a precursor of 3. Cluster 2 is formed via oxidative-addition of E–H bond to 1 whose decarbonylation leads to the formation of 3. The molecular structures of all the new clusters (except 3c) have been determined by X-ray crystallography. Both 2 and 3 exist as a pair of isomers in solution, and their fluxionality in solution has been probed by VT NMR experiments. [ABSTRACT FROM AUTHOR]

The reaction of the electron-deficient 6-methoxyquinolinate-substituted triosmium cluster [Os 3 (CO) 9 {μ 3 -η 1 ,κ 1 -C 9 H 5 N(6-OMe)}(μ-H)] ( 1 ) with PPh 3 proceeds readily at room temperature to afford the electron-precise adduct [Os 3 (CO) 9 (PPh 3 ){μ-η 1 ,κ 1 -C 9 H 5 N(6-OMe)}(μ-H)] ( 2 ), in which the PPh 3 ligand is bound to the osmium that serves as the coordination site for the hydride and the metallated-carbon atom of the benzoheterocycle. This reaction also leads to a change in the hapticity of the 6-methoxyquinolinate ligand from μ 3 -η 1 ,κ 1 to μ-η 1 ,κ 1 as confirmed by X-ray crystallography. Thermolysis of 2 in boiling toluene furnishes five new triosmium clusters ( 3 – 7 ) as a result of ligand isomerization, decarbonylation and orthometallation of the ancillary PPh 3 ligand. Clusters 3 and 4 are isomers of 2 and the location of the metal-bound hydride and PPh 3 with respect to 6-methoxyquinolinate moiety is the only difference between these isomers. Control experiments show that 5 is a decarbonylation product of 4 which converts into 6 as a result of further decarbonylation with concomitant orthometallation of one of the phenyl rings of the coordinated PPh 3 ligand, whilst 7 is formed from 6 through replacement of an equatorial carbonyl of the nitrogen-bound osmium by PPh 3 ligand. All the new clusters have been characterized by a combination of analytical and spectroscopic methods as well as by X-ray crystallography in the case of 2 , 3 , 6 and 7 . [ABSTRACT FROM AUTHOR]

Reactions of Ru3(CO)10(µ-dppf) (1) (dppf = 1,1'-bis(diphenylphosphino)ferrocene), Ru3(CO)10(µ-dppm) (2) (dppm = bis(diphenylphosphino)methane), and the orthometalated derivative Ru3(CO)9{µ3- PPhCH2PPh(C6H4)} (3) with silanes (Ph3SiH, Et3SiH, Ph2SiH2) are reported. Treatment of 1 with Ph3SiH and Ph2SiH2 at room temperature leads to facile Si--H bond activation to afford Ru3(CO)9(µ-dppf)(SiPh3)(µ-H) (4) (60% yield) and Ru3(CO)9(µ-dppf)(SiPh2H)(µ-H) (6) (53% yield), respectively. The reaction of 1 with Ph3SiH has been investigated by electronic structure calculations, and these data have facilitated the analysis of the potential energy surface leading to 4. Compound 1 does not react with Et3SiH at room temperature but reacts at 68 °C to give Ru3(CO)9(µ-dppf)(SiEt3)(µ-H) (5) in 45% yield. Reaction of 2 with Ph3SiH at room temperature yields two new products: Ru3(CO)9(µ-dppm)(SiPh3)(µ-H) (7) in 40% yield and Ru3(CO)6(µ3-O)(µ-dppm)(SiPh3)(µ- H)3 (8) in 15% yield. Interestingly, at room temperature compound 7 slowly reverts back to 2 in solution with decomposition and liberation of Ph3SiH. Complex 8 can also be prepared from the direct reaction between 7 and H2O. Similar reactions of 2 with Et3SiH and Ph2SiH2 give only intractable materials. The orthometalated compound 3 does not react with Ph3SiH, Et3SiH and Ph2SiH2 at room temperature but does react at 66 °C to give Ru3(µ-CO)(CO)7{µ3- PPhCH2PPh(C6H4)}(SiR2R¹)(µ- H)](9, R = R' = Ph, 71% yield; 10, R = R' = Et, 60% yield; 11, R = Ph, R' = H, 66% yield) by activation of the Si--H bond. Compounds 4 and 8--11 have been structurally characterized. In 4, both the dppf and the hydride bridge a common Ru--Ru vector, whereas NMR studies on 7 indicate that two ligands span different Ru--Ru edges. Compound 8 contains a face-capping oxo moiety, a terminally coordinated SiPh3 ligand, and three bridging hydride ligands, whereas 9--11 represent simple oxidative addition products. In all of the compounds examined, the triruthenium framework retains its integrity and the silyl groups occupy equatorial sites. [ABSTRACT FROM AUTHOR]

Abstract: Upon mild heating (60–65°C), electron-deficient [Os3(CO)9(μ3-C7H4NS)(μ-H)] (1) readily adds to the activated alkyne, RChsp sp="0.25" />=CO2Me), to give two isomers of the alkenyl complexes, [Os3(CO)9(μ-C7H4NS)(μ3-RCCHR)] (2 and 3), differing in the orientation of the benzothiazole ligand. In both the alkenyl ligand acts as a five-electron donor binding through both carbons and one of the oxygen atoms of the substituents, which adopt a relative cis disposition. Heating 2 cleanly affords 3 suggesting that the former is the kinetic product and the latter is thermodynamically favoured. At higher temperatures (110°C), 3 rearranges to a third isomer [Os3(CO)9(μ-C7H4NS)(μ-RCCHR)] (4) which differs in the binding mode of the alkenyl ligand and where the alkyne substituents are in a relative trans disposition. A second product of this reaction is [Os3(CO)8(μ-OCH3){μ3-C7H4NSC(R)C}(μ-H)] (5) which results from the loss of two moles of CO, carbon–carbon coupling between hydrocarbyl and benzothiazole ligands and carbon–hydrogen addition to the triosmium centre. All new clusters are characterized by a total of 50 valence electrons and contain two metal–metal bonds as shown by single crystal X-ray diffraction studies. [Copyright &y& Elsevier]

Abstract: Treatment of unsaturated [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (2) with t BuNC at room temperature gives [Os3(CO)8(CNBu t )){μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os3(CO)7(CNBu t ){μ3-Ph2PCHP(Ph)C6H4}(μ-H)2] (4). Reaction of the labile complex [Os3(CO)9(μ-dppm)(NCMe)] (5) with t BuNC at room temperature affords the substitution product [Os3(CO)9(μ-dppm)(CNBu t )] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os3(CO)9{μ3-η2-C7H3(2-Me)NS}(μ-H)] (7) with t BuNC yields the addition product [Os3(CO)9(CNBu t ){μ-η2-C7H3(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os3(CO)8(CNBu t ){μ3-η2-C7H3(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh3 at room temperature to give the adduct [Os3(CO)8(PPh3)(CNBu t ){μ-η2-C7H3(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies. [Copyright &y& Elsevier]

Abstract: Treatment of [(μ-H)Os3(CO)10(μ-OMe)] (1) with dppm {dppm=bis(diphenylphosphino)methane} at 110°C gave the known compound [Os3(CO)10(μ2-η2-dppm)] (2) and the new compound [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppm)] (3). A similar reaction of 1 with dppe {dppe=bis(diphenylphosphino)ethane} afforded two products, [(μ-H)Os3(CO)8(μ-OMe)(μ1-η2-dppe)] (5) and [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppe)] (6) which differ in the mode of bonding of the dppe ligand. The reaction of 1 with dppp {dppp=bis(diphenylphosphino)propane} at 110°C gave exclusively [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppp)] (7) which exists as two isomers in solution. Compounds 2, 3, and 5–7 are also obtained in almost similar yields from reactions of [(μ-H)Os3(CO)9(μ-OMe)(MeCN)] (4) with the appropriate diphosphine at ambient temperature. The reaction of 1 with PPh2H at 110°C gave the new compounds [(μ-H)Os3(CO)9(μ-OMe)(PPh2H)] (8) and [(μ-H)2Os3(CO)7(μ-PPh2)2(PPh2H)] (10) and the previously reported compound [(μ-H)2Os3(CO)8(μ-PPh2)2] (9). The molecular structures of 3 and 8 were determined by single crystal X-ray diffraction. In compound 3, the dppm ligand bridges the same Os–Os edge as the hydride and the methoxide ligand. In 8, the PPh2H ligand occupies a ‘pseudo’ axial site on one of the osmium atoms bearing the bridging hydride and methoxide ligand. [Copyright &y& Elsevier]

Abstract: Heating [Os3(CO)10(μ-dppm)] (1) with two equivalents of PhSSPh in toluene under reflux provided three new triosmium compounds [(μ-H)Os3(CO)7(μ-SPh){μ3-η4-Ph2PCHP(Ph)C6H4}] (2), [Os3(CO)8(μ-SPh)2(μ-dppm)] (3) and [(μ-H)Os3(CO)7(μ-η2-SC6H4)(μ-SPh)(μ-dppm)] (4) in 20%, 21% and 26% yields, respectively. In contrast, a similar reaction of 1 with two equivalents of PhTeTePh in refluxing toluene gave the binuclear compound [Os2(CO)4(μ-TePh)2(μ-dppm)] (6) in 15% yield, and two 50 electron isomeric compounds 5 and 7 with the formula [Os3(CO)8(μ-TePh)2(μ-dppm)] in 20% and 23% yields, respectively. Thermolysis of 3 at 110°C afforded 4 in 53% yield which on further thermolysis in refluxing octane at 128°C gave 2 in 45% yield. Thermolysis of 3 in refluxing octane also gave 2 in 50% yield. The new compounds, 2–7, were all spectroscopically characterized, and the X-ray structures of 2, 3 and 7 have been determined. Compound 2 contains a bridging SPh ligand and a μ3,η4-Ph2PCHP(Ph)C6H4 ligand, formed by two kinds of C–H activation, including orthometallation of a phenyl group as well as an unusual activation of the methylene group of the dppm ligand. The molecular structure of 3 reveals that two SPh groups span the open Os–Os edge of the Os3 triangle, while the dppm ligand bridges one of the closed Os–Os edges. In compound 7, one TePh group spans the open Os–Os edge, while the other spans one of the two closed Os–Os edges and the dppm ligand bridges the third Os–Os vector. [Copyright &y& Elsevier]

Abstract: Treatment of the electronically unsaturated cluster [(μ-H)Os3(CO)8(Ph2PCH2P(Ph)C6H4)] (1) with HCl gas at ambient temperature in dichloromethane afforded (μ-H)Os3(CO)8(μ-Cl)(μ-dppm) (2) and [(μ-H)Os3(CO)7(η1-Cl)(μ-Cl)2(μ-dppm)] (3). Thermolysis of 2 at 110 °C led to an isomer of 2, 4. A similar reaction of 1 with HBr gas gave [(μ-H)Os3(CO)8(μ-Br)(μ-dppm)] (5) as the only product which does not isomerize at 110 °C. In sharp contrast, treatment of 1 with HF gas gave the protonated species [(μ-H)2Os3(CO)8(Ph2PCH2P(Ph)C6H4)]+ (6). Treatment of 1 with CF3CO2H also gave cation 6 whereas CH3CO2H yielded [(μ-H)Os3(CO)8(μ-η2-CH3CO2)(μ-dppm)] (7). Structures of 2, 3, 4 and 6 were established crystallographically. In 2, both the chloride and the hydride ligands simultaneously bridge the same Os–Os edge and the dppm spans another Os–Os bond whereas in 4, all the three ligands bridge the same Os–Os edge. Compound 3 is comprised of an open Os3 arrangement in which one chloride bridges the open Os⋯Os edge, another chloride and a hydride mutually bridge an Os–Os bond and the third chloride is terminally coordinated to one of the Os atoms of the dppm bridged edge. The cation 6 consists of a triangle of osmium atoms in which the shortest Os–Os edge is bridged by a hydride and the metallated phenyl ring and the longest edge is bridged by another hydride and the diphosphine ligand. [Copyright &y& Elsevier]

Abstract: We have studied the ability of several bioorganometallic clusters [(μ-H)Os3(CO)9(L)(μ3-η2-(Q-H))], where L=[P(C6H4SO3Na)3] or [P(OCH2CH2NMe3I)3], and Q=quinoline, 3-aminoquinoline, quinoxaline or phenanthridine, of inhibiting telomerase, a crucial enzyme for cancer progression. In general, quinolines have shown interesting biological properties, especially in inhibiting enzymes. For example, the 2,3,7-trichloro-5-nitroquinoxaline (TNQX) exhibited strong anti-telomerase activity in vitro. Among the quinoline-clusters under study, only the negatively charged ones (by virtue of the sulfonated phosphines) exhibited good anti-telomerasic activity on semi-purified enzyme in a cell-free assay, while they were ineffective in vitro on Taq, a different DNA-polymerase. On the contrary, the treatment of breast cancer MCF-7 cell line did not evidence any activity of these clusters, suggesting a low aptitude for crossing cell membrane. Furthermore, all clusters exhibited non-specific, acute cytotoxicy, probably due to accumulation on cell membranes by virtue of their amphiphilic character. A detailed study of Os uptake and accumulation in MCF-7 cells supported this hypothesis. [Copyright &y& Elsevier]

The reaction of [Ru3(CO)10(mu-dppm)] (1) with dppmSe at 66 °C affords [Ru3(CO)8(mu-dppm)2] (2), [Ru3(CO)7(mu3-CO)(mu3-Se)(mu-dppm)] (3), [Ru3(CO)5(mu3-CO)(mu3-Se)(mu-dppm)2] (4) and [Ru3(CO)6(mu3-CO)(mu3-Se)(mu-dppm)(mu1-Ph2PCH2P(double bond; length as m-dashO)Ph2)] (5) in 7%, 5%, 9% and 33% yields, respectively. A similar reaction between 1 with dppmS gives [Ru3(CO)7(mu3-S)2(mu-dppm)] (6), [Ru3(CO)7(mu3-CO)(mu3-S)(mu-dppm)] (7) [Ru3(CO)5(mu3-CO)(mu3-S)(mu-dppm)2] (8) and [Ru3(CO)6(mu3-CO)(mu3-S)(mu-dppm)(mu1-Ph2PCH2P(double bond; length as m-dashO)Ph2)] (9) in 8%, 7%, 14% and 35% yields, respectively. Treatment of 1 with PhSeSePh at 66 °C affords the dinuclear compound [Ru2(CO)4(mu-SePh)2(mu-dppm)] (10) in 14% yield. Thermolysis of 5 and 9in refluxing toluene at 110 °C gives 4 and 8, respectively. The molecular structures of 4, 9 and 10 have been determined by single-crystal X-ray diffraction studies. The cores of the new clusters 4, 5, 8 and 9 consist of metal triangles capped by mu3-sulfur or selenium atoms with the bidentate ligand bridging in equatorial positions. In compounds 4 and 8, two bidentate dppm ligands bridge the Ru3 triangle in such a way that each ligand bridges two ruthenium atoms and one Ru-Ru edge remains unbridged. Compounds 5 and 9 contain one bridging dppm ligand and one dangling dppm mono-oxide ligand Ph2PCH2P(double bond; length as m-dashO)Ph2 coordinated to the rear metal atom at an equatorial position. The molecular structure of 10 shows classical "sawhorse" structure with two bridging SePh ligands as well as the dppm ligand. [ABSTRACT FROM AUTHOR]

The reactions of [Os3(CO)10(MeCN)2], [Ru3(CO)12], [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}], [Os3(CO)10(μ-dppm)] and [Ru3(CO)10(μ-dppm)] with 2-mercapto-1-methylimidazole are reported. The labile cluster [Os3(CO)10(MeCN)2] reacts with 2-mercapto-1-methylimidazole at 25 °C to give [(μ-H)Os3(CO)10{μ-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)}] (1) whereas the corresponding reaction of [Ru3(CO)12] with the ligand at 68 °C gives [(μ-H)Ru3(CO)9{μ3-η2-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)}] (2). Both [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}] and [Os3 (CO)10(μ-dppm)] react with 2-mercapto-1-methylimidazole at 25 and 110 °C, respectively, to give [(μ-H)Os3(CO)8{μ-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)(μ-dppm)] (3). In contrast [Ru3(CO)10(μ-dppm)] reacts with 2-mercapto-1-methylimidazole at 68 °C to yield the known compound [Ru3(CO)7(μ3-CO)(μ3-S)(μ-dppm)] (4). The structures of 1–3 have been determined by X-ray crystallography. [Copyright &y& Elsevier]