Supramolecular Aggregates of Complex Cations via Unusual Purine−Purine Base Pairing in a New Organorhodium(III) Compound Containing the Antileukemic Drug Purine-6-thione. Synthesis, X-ray Structure of <i>trans</i>(<i>C</i>,<i>N</i><i>⁷</i>),<i>trans</i>(<i>S</i>,<i>S</i>),<i>trans</i>(<i>P</i>,<i>N</i><i>⁷</i>)-[Rh(C₆H₅)(H¹,H⁹- H₂tp)₂(PPh₃)][Rh(C₆H₅)(H¹,H⁹-H₂tp)(H⁹- Htp)(PPh₃)]Cl₃·HCl·6H₂O, and Density Functional Analysis of the {H₂tp···Htp}^- Base Pair

Supramolecular Aggregates of Complex Cations via Unusual Purine−Purine Base Pairing in a New Organorhodium(III) Compound Containing the Antileukemic Drug Purine-6-thione. Synthesis, X-ray Structure of trans(C,N7),trans(S,S),trans(P,N7)-[Rh(C6H5)(H1,H9- H2tp)2(PPh3)][Rh(C6H5)(H1,H9-H2tp)(H9- Htp)(PPh3)]Cl3·HCl·6H2O, and Density Functional Analysis of the {H2tp···Htp}- Base Pai

Supramolecular Aggregates of Complex Cations via Unusual Purine−Purine Base Pairing in a New Organorhodium(III) Compound Containing the Antileukemic Drug Purine-6-thione. Synthesis, X-ray Structure of <i>trans</i>(<i>C</i>,<i>N</i><i>⁷</i>),<i>trans</i>(<i>S</i>,<i>S</i>),<i>trans</i>(<i>P</i>,<i>N</i><i>⁷</i>)-[Rh(C₆H₅)(H¹,H⁹- H₂tp)₂(PPh₃)][Rh(C₆H₅)(H¹,H⁹-H₂tp)(H⁹- Htp)(PPh₃)]Cl₃·HCl·6H₂O, and Density Functional Analysis of the {H₂tp···Htp}^- Base Pair

Supramolecular Aggregates of Complex Cations via Unusual Purine−Purine Base Pairing in a New Organorhodium(III) Compound Containing the Antileukemic Drug Purine-6-thione. Synthesis, X-ray Structure of trans(C,N7),trans(S,S),trans(P,N7)-[Rh(C6H5)(H1,H9- H2tp)2(PPh3)][Rh(C6H5)(H1,H9-H2tp)(H9- Htp)(PPh3)]Cl3·HCl·6H2O, and Density Functional Analysis of the {H2tp···Htp}- Base Pai

Polynuclear Metallacarborane−Hydrocarbon Assemblies: Metallacarborane Dendrimers¹

The first dendrimers containing metallacarborane modules have been prepared and characterized. The acyl derivative nido-[η5-C5H4C(O)Cl]Co(2,3-Et2C2B3H5) was treated with diaminobutane-dend(NH2)16 (DAB-16) and Et3N in CH2Cl2 to give the 16- and 32-cobalt metallodendrimers DAB-dend-[NHC(O)-C5H4Co(2,3-Et2C2B3H5)]16 (5) and DAB-dend-[NHC(O)-C5H4Co(2,3-Et2C2B3H5)]32 (6), which were isolated as air-stable yellow solids in 76% and 79% yields, respectively

Polynuclear Metallacarborane−Hydrocarbon Assemblies: Metallacarborane Dendrimers¹

The first dendrimers containing metallacarborane modules have been prepared and characterized. The acyl derivative nido-[η5-C5H4C(O)Cl]Co(2,3-Et2C2B3H5) was treated with diaminobutane-dend(NH2)16 (DAB-16) and Et3N in CH2Cl2 to give the 16- and 32-cobalt metallodendrimers DAB-dend-[NHC(O)-C5H4Co(2,3-Et2C2B3H5)]16 (5) and DAB-dend-[NHC(O)-C5H4Co(2,3-Et2C2B3H5)]32 (6), which were isolated as air-stable yellow solids in 76% and 79% yields, respectively

A Complete Family of Isostructural Cluster Compounds with Cubane-like M₃S₄M‘ Cores (M = Mo, W; M‘ = Ni, Pd, Pt): Comparative Crystallography and Electrochemistry

By reaction of the geometrically incomplete cubane-like clusters [(η5-Cp‘)3Mo3S4)][pts] and [(η5-Cp‘)3W3S4][pts] (Cp‘ = methylcyclopentadienyl; pts = p-toluenesulfonate) with group 10 alkene complexes, three new heterobimetallic clusters with cubane-like cluster cores were isolated:  [(η5-Cp‘)3W3S4M‘(PPh3)][pts] ([5][pts], M‘ = Pd; [6][pts], M‘ = Pt); [(η5-Cp‘)3Mo3S4Ni(AsPh3)][pts] ([7][pts]). The compounds [5][pts]−[7][pts] are completing the extensive series of clusters [(η5-Cp‘)3M3S4M‘(EPh3)][pts] (M = Mo, W; M‘ = Ni, Pd, Pt; E = P, As) which allows the consequences of replacing a single type of atom on structural and NMR and UV/vis spectroscopic as well as electrochemical properties to be determined. Single-crystal X-ray structure determinations of [5][pts]−[7][pts] revealed that [5][pts] was not isomorphous to the other members of the series [(η5-Cp‘)3M3S4M‘(EPh3)][pts] due to distinctly different cell parameters, which in the molecular structure of [5]+ is reflected in a slightly different orientation of the PPh3 ligand. Electrochemical measurements on the series showed that the Mo-based clusters were more difficult to oxidize than their W-based analogues. The Pd-containing clusters underwent two-electron oxidation processes, whereas the Ni- and Pt-containing clusters underwent two separated one-electron oxidation processes

A Complete Family of Isostructural Cluster Compounds with Cubane-like M₃S₄M‘ Cores (M = Mo, W; M‘ = Ni, Pd, Pt): Comparative Crystallography and Electrochemistry

By reaction of the geometrically incomplete cubane-like clusters [(η5-Cp‘)3Mo3S4)][pts] and [(η5-Cp‘)3W3S4][pts] (Cp‘ = methylcyclopentadienyl; pts = p-toluenesulfonate) with group 10 alkene complexes, three new heterobimetallic clusters with cubane-like cluster cores were isolated:  [(η5-Cp‘)3W3S4M‘(PPh3)][pts] ([5][pts], M‘ = Pd; [6][pts], M‘ = Pt); [(η5-Cp‘)3Mo3S4Ni(AsPh3)][pts] ([7][pts]). The compounds [5][pts]−[7][pts] are completing the extensive series of clusters [(η5-Cp‘)3M3S4M‘(EPh3)][pts] (M = Mo, W; M‘ = Ni, Pd, Pt; E = P, As) which allows the consequences of replacing a single type of atom on structural and NMR and UV/vis spectroscopic as well as electrochemical properties to be determined. Single-crystal X-ray structure determinations of [5][pts]−[7][pts] revealed that [5][pts] was not isomorphous to the other members of the series [(η5-Cp‘)3M3S4M‘(EPh3)][pts] due to distinctly different cell parameters, which in the molecular structure of [5]+ is reflected in a slightly different orientation of the PPh3 ligand. Electrochemical measurements on the series showed that the Mo-based clusters were more difficult to oxidize than their W-based analogues. The Pd-containing clusters underwent two-electron oxidation processes, whereas the Ni- and Pt-containing clusters underwent two separated one-electron oxidation processes

Synthesis, Structural Characterization, Solution Chemistry, and Preliminary Biological Studies of the Ruthenium(III) Complexes [TzH][<i>trans</i>-RuCl₄(Tz)₂] and [TzH][<i>trans</i>-RuCl₄(DMSO)(Tz)]·(DMSO), the Thiazole Analogues of Antitumor ICR and NAMI-A

Two ruthenium(III) complexes bearing the thiazole ligand, namely, thiazolium (bisthiazole) tetrachlororuthenate (I, TzICR) and thiazolium (thiazole, DMSO) tetrachlororuthenate (II, TzNAMI) were prepared and characterized. The crystal structures of both complexes were solved by X-ray diffraction methods and found to match closely those of the corresponding imidazole complexes. The behavior in aqueous solution of bothTzICR and TzNAMI was analyzed spectroscopically. The time-dependent spectrophotometric profiles resemble closely those of the related ICR and NAMI-A anticancer compounds, respectively. It is observed that replacement of imidazole with thiazole, a less basic ligand, produces a significant decrease of the ligand exchange rates in the case of the NAMI-like compound. The main electrochemical features of these ruthenium(III) thiazole complexes were determined and compared to those of ICR and NAMI-A. Moreover, some preliminary data were obtained on their biological properties. Notably, both complexes exhibit higher reactivity toward serum albumin than toward calf thymus DNA; cytotoxicity is negligible in line with expectations. A more extensive characterization of the pharmacological properties in vivo is presently in progress

Electronic Properties of Mononuclear, Dinuclear, and Polynuclear Cobaltacarboranes: Electrochemical and Spectroelectrochemical Studies

Electronic interactions and metal−metal communication in a wide range of cobaltacarborane−hydrocarbon complexes containing one to six metal centers, and exhibiting a variety of modes of inter-cage connectivity and molecular architectures, have been investigated via cyclic voltammetry, controlled potential coulometry, and UV−visible spectroelectrochemistry. The properties of mixed-valent CoIII/CoIV and CoII/CoIII species that are generated on oxidation or reduction of dinuclear and polynuclear CoIII complexes were examined and classified as Robin-Day Class I (localized), Class II (partially delocalized), or Class III (fully delocalized) systems. The extent of metal−metal communication between metallacarborane cage units is strongly influenced by the type of intercage connection (e.g., cage B−B or Cp−Cp); the vertexes involved (equatorial vs apical); the nature of the linking unit, if any; and the presence of substituents on the carborane cages. In multi-tripledecker complexes where three CpCo(C2B3H4)CoCp units are linked through a central triethynyl benzene connector, the data suggest that Co−Co electronic communication is extensive (Class III) within individual sandwich units while intersandwich delocalization is weak or absent. An extended Hückel study of CpCoC2B4H6 double-decker and CpCo(C2B3H5)CoCp triple-decker sandwich model complexes shows significant differences in the orbital contributions involved in the HOMO and LUMO of the former vs the latter type. The calculations afford additional insight into the electronic structures and properties of these systems as elucidated by the experimental studies

Gold(III) Dithiocarbamate Derivatives for the Treatment of Cancer: Solution Chemistry, DNA Binding, and Hemolytic Properties

Gold(III) compounds are emerging as a new class of metal complexes with outstanding cytotoxic properties and are presently being evaluated as potential antitumor agents. We report here on the solution and electrochemical properties, and the biological behavior of some gold(III) dithiocarbamate derivatives which have been recently proved to be one to 4 orders of magnitude more cytotoxic in vitro than the reference drug (cisplatin) and to be able to overcome to a large extent both intrinsic and acquired resistance to cisplatin itself. Their solution properties have been monitored in order to study their stability under physiological conditions; remarkably, they have shown to undergo complete hydrolysis within 1 h, the metal center remaining in the +3 oxidation state. Their DNA binding properties and ability in hemolyzing red blood cells have been also evaluated. These gold(III) complexes show high reactivity toward some biologically important isolated macromolecules, resulting in a dramatic inhibition of both DNA and RNA synthesis and inducing DNA lesions with a faster kinetics than cisplatin. Nevertheless, they also induce a strong and fast hemolytic effect (compared to cisplatin), suggesting that intracellular DNA might not represent their primary or exclusive biological target

Inverted Ligand Field in a Pentanuclear Bow Tie Au/Fe Carbonyl Cluster

Gold chemistry has experienced in the last decades exponential attention for a wide spectrum of chemical applications, but the +3 oxidation state, traditionally assigned to gold, remains somewhat questionable. Herein, we present a detailed analysis of the electronic structure of the pentanuclear bow tie Au/Fe carbonyl cluster [Au­{η2-Fe2(CO)8}2]− together with its two one-electron reversible reductions. A new interpretation of the bonding pattern is provided with the help of inverted ligand field theory. The classical view of a central gold­(III) interacting with two [Fe2(CO)8]2– units is replaced by Au­(I), with a d10 gold configuration, with two interacting [Fe2(CO)8]− fragments. A d10 configuration for the gold center in the compound [Au­{η2-Fe2(CO)8}2]− is confirmed by the LUMO orbital composition, which is mainly localized on the iron carbonyl fragments rather than on a d gold orbital, as expected for a d8 configuration. Upon one-electron stepwise reduction, the spectroelectrochemical measurements show a progressive red shift in the carbonyl stretching, in agreement with the increased population of the LUMO centered on the iron units. Such a trend is also confirmed by the X-ray structure of the direduced compound [Au­{η1-Fe2(CO)8}­{η2-Fe2(CO)6(μ-CO)2}]3–, featuring the cleavage of one Au–Fe bond