Mono-and polynuclear CoII complexes with 2-hydroxy-6-methylpyridine

The reaction of 2-hydroxy-6-methylpyridine with Co(NO₃)₂·6H₂O or Co(F₃CSO₃)₂·6H₂O in the absence of a deprotonating agent produces the mononuclear complexes Co(HL)₄(NO₃)₂ or Co(HL)₄(F₃CSO₃)₂ (HL is 6-methyl-2-pyridone), respectively. In the presence of triethylamine, the reaction affords the trinuclear complex Co₃(HL)₂(L)₄(NO₃)₂ or the heptanuclear dicationic complex [Co₇L₁₂]·(F₃CSO₃)₂·4MeCN in the case of cobalt nitrate or cobalt trifluoromethanesulfonate, respectively. When HL is deficient, the replacement of the trimethylacetate anions in polymeric cobalt pivalate [Co(OH)_n(OOCCMe₃)_2−n ]_x gives rise to the hexanuclear complex Co₆(μ₃-OH)₂(η²,μ₃-L)₂(μ-OOCCMe₃)₈(HOOCCMe₃)₄, whereas the HLCo₆(μ₃-OH)(η²,μ₃-L)₃(η²,μ-L) (μ₃-L)(μ₃-OOCCMe₃)(μ-OOCCMe₃)₄(η²-OOCCMe₃) complex is generated when HL is present in excess. The structures of the reaction products were established by X-ray diffraction. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1851–1862, November, 2006.     

Trimethylacetate nickel complexes

The present review is devoted to the chemistry of trimethylacetate Ni^II complexes with various nitrogen-containing ligands. Pathways of formation of complexes containing the Ni₂(μ-OH₂)(μ-OOCCMe₃)₂ and Ni₂(μ-OOCCMe₃)₄ fragments are discussed. Pathways of degradation of the nine-nuclear complex Ni₉(HOOCCMe₃)₄(μ₄-OH)₃(μ₃-OH)₃)₃(μ₄-OOCCMe₃)₁₂ under the action of primary amines (aniline or propargylamine) as well as the process of dehydration ofN-phenyl-o-phenylenediamine up to the bischelate mononuclear complex [1,2-(NH)(NPh)C₆H₄]₂Ni are demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–419, March, 1999.     

Synthesis and structures of nickel(II) trimethylacetate dimers with coordinated diamines

Thermal decomposition of the tetranuclear nickel(II) complex Ni₄lη²-o-(NH₂)(NHPh)C₆H₄|₂(MeCN)₂(μ-OOCCMe₃)₄(η²-OOCCMe₃)₂ (I) under an inert atmosphere (o-xylene, 140 °C) was investigated. Under these conditions, the asymmetric binuclear complex Ni|η²-o-(NH₂)(NHPh)C₆H₄‖(η¹-o-(NH₂))(NHPh)C₆H₄|(η²,η-O,O-OOCCMe₃)(η²-OOCCMe₃) (2) was formed at the first stage. Complex2 was converted into the symmetric dimer Ni|η¹-o-(NH₂)(NHPh)C₆H₄|(μ-OOCCMe₃)₄ (3) upon recrystallization from benzene. The structures of complexes2 and3 were established by X-ray diffraction analysis. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1915–1918, November, 2000.     

Role of metal center in reactions of polynuclear nickel(ii) and cobalt(ii) trimethylacetates with 8-amino-2,4-dimethylquinoline

The reactions of 8-amino-2,4-dimethylquinoline (L) (1) with polynuclear nickel(ii) and cobalt(ii) hydroxotrimethylacetato complexes under anaerobic conditions were studied. The nonanuclear cluster Ni₉(₄-OH)₃(₃-OH)₃(_n-OOCCMe₃)₁₂(HOOCCMe₃)₄ gave the mononuclear complex Ni(²-L)(²-OOCCMe₃)₂ (2). The tetranuclear complex Ni₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ produced the mononuclear complex Ni(²-L)(²-OOCCMe₃)(OOCCMe₃)L (3). At room temperature, the cobalt-containing polynuclear trimethylacetates, viz., the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x and the tetranuclear complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆, were transformed into the trinuclear cobalt(ii) complex Co₃(₃-OH)(-OOCCMe₃)₄(²-L)₂(OOCCMe₃) (4). Meanwhile, at 80 °C these compounds generated the binuclear cobalt(iii) complex Co₂(₂²-(HN)C₉NMe₂)₂(-OOCCMe₃)(L)(OOCCMe₃)₃ (5). The structures of the resulting compounds were established by X-ray diffraction analysis. Compounds 2—4 exhibit the antiferromagnetic spin-spin exchange coupling, whereas compound 5 is diamagnetic.     

Synthesis, structures, and magnetic properties of binuclear carboxylate complexes with NiII and NiIII atoms

The reaction of NiCl₂·6H₂O with Me₃CCOOH and KOH taken in a molar ratio of 1:2:2 in water afforded the nonanuclear antiferromagnetic complex Py₂Ni₂(Me₃CCOOH)₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH₂), which apparently contains Ni^II and Ni^III atoms. The complex was isolated by extraction with CH₂Cl₂, benzene, or hexane. The reactions of this complex with pyridine bases (pyridine (Py), 3,4-lutidine (Lut), and nicorandil (Nic)) gave the adducts L₄Ni₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH) (L=Py, Lut, or Nic, respectively). According to magnetic measurements, intramolecular ferromagnetic exchange interactions in these adducts are complemented by intermolecular antiferromagnetic interactions. Pyrolysis of the pyridine adduct in air or under an inert atmosphere in xylene yielded the antiferromagnetic complex Py₂Ni₂(Me₃CCOOH)₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH₂), which contains Ni^II atoms. The structures of all the complexes synthesized were established by X-ray diffraction analysis. The electronic absorption spectra of these compounds are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–738, April, 1998.     

New cobalt trimethylacetate complexes with pyridine

The reaction of the tetranuclear trimethylacetate complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ with pyridine in acetonitrile was studied. Two new compounds, viz., the hexanuclear cobalt(ii) complex Co₆py₄(₃-OH)₂(-OOCCMe₃)₁₀ (25% yield) and the unusual ionic compound [Co₃py₃(₃-O)(-OOCCMe₃)₆]⁺[Co₄py(₄-O)(-OOCCMe₃)₇]^– (5% yield), were prepared. The structures of the new compounds were established by X-ray diffraction analysis.     

High-spin carboxylate polymers [M(OOCCMe3)2]n of group VIII 3d metals

A coordination polymer of the general formula [Co(OOCCMe₃)₂]_n (2) was prepared by mild thermolysis of the coordination polymer of variable composition [(HOOCCMe₃)_xCo(OH)_n(OOCCMe₃)_2−n ]_m, the dinuclear cobalt complex Co₂(μ-H₂O)(OOCCMe₃)₄(HOOCCMe₃)₄, the tetranuclear cobalt cluster Co₄(μ₃-OH)₂(OOCCMe₃)₆(HOEt)₆, and the hexanuclear cluster [Co₆(μ₄-O)₂(μ_n-OOCCMe₃)₁₀(C₄H₈O)₃(H₂O)]·1.5(C₄H₈O) (7) in organic solvents. In the crystal, the polymer has a chain structure. Unlike thermolysis of cobalt pivalates, thermolysis of the dinuclear complex Ni₂(μ-H₂O)(OOCCMe₃)₄(HOOCCMe₃)₄ gave rise to the hexanuclear complex Ni₆(μ₂-OOCCMe₃)₆(μ₃-OOCCMe₃)₆ (3). The magnetic properties of compound 2 are substantially different from those of 3. Compound 2 undergoes the magnetic phase transition into the ordered state at T _c = 3.4 K (H = 1 Oe), whereas compound 3 exhibits antiferromagnetic properties. Solid-state decomposition of polymeric cobalt carboxylate 2 (below 350 °C) afforded the octanuclear cluster Co₈(μ₄-O)₂(μ₂-OOCCMe₃)₆(μ₃-OOCCMe₃)₆ (9) as the major product, which sublimes without decomposition. Decomposition of 3 gave nickel oxide as the final product. Pivalates 2 and 3 reacted with 2,3-lutidine in acetonitrile at 80 °C to form the isostructural dinuclear complexes (2,3-Me₂C₅H₃N)₂M₂(μ-OOCCMe₃)₄ (M = Co or Ni). The structures of compounds 3 and 7 were established by X-ray diffraction. The structure of polymer 2 was determined by powder X-ray diffraction analysis. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1841–1850, November, 2006.     

Formation of cobalt(iii) cations with semiquinonediimine ligands

The reactions of polynuclear cobalt(ii) trimethylacetates [Co(OH) _n (OOCCMe₃)_2–n ] _x , Co₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄, or Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with an excess of N-phenyl-o-phenylenediamine (1) in toluene followed by treatment with atmospheric oxygen afforded the diamagnetic complex [Co{²-(NPh)(NH)C₆H₄}₂{¹-(NH₂)C₆H₄(NPhH)}]⁺(Me₃CCOO...H...OOCCMe₃)^– (3), whose cation contains the Co^III atom. The reaction of Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with a deficient amount of diamine 1 in acetonitrile under an argon atmosphere gave rise to the antiferromagnetic ionic complex [Co{²-(NPh)(NH)C₆H₄}₂MeCN]⁺[Co₂(₂,²-OOCCMe₃)(₂-OOCCMe₃)₂(²-OOCCMe₃)₂]^–·2MeCN (4), whose cation is an isoelectronic analog of the cation in complex 3. The structures of the new compounds were established by X-ray diffraction analysis.     

New cobalt and iron pivalate complexes with 2,2′:6′,2″-terpyridine: synthesis, structure, and magnetic properties

The mononuclear complexes (η³-terpy)M(Piv)²·MeCN (M = Fe ⁱⁱ (3) and Co ⁱⁱ (4), and Piv is the pivalate anion) were synthesized by the reactions of polymeric iron(ii) and cobalt(ii) pivalates with 2,2′:6′,2″-terpyridine (terpy). The oxidation of compound 3 affords the pentanuclear heterospin iron(ii,iii) complex (η³-terpy)Fe₅(μ₄-O)(μ₃-OH)(μ-OH)₂(μ-Piv)₇(η¹-Piv)₂ (5). All compounds were characterized by X-ray diffraction. Dedicated to the 90th anniversary of the L. Ya. Karpov Institute of Physical Chemistry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1186–1190, June, 2008.     

Formation of cobalt- and lithium-containing heterometallic pyridonate carboxylate coordination polymers

The reaction of cobalt(II) chloride with 2-hydroxypyridine (Hhp) and lithium pivalate in acetonitrile affords the 1D polymer [Li₃CoCl(μ-Piv)(μ₃-Piv)₂(μ₃,η²-Piv)(μ-Hhp)₂(η¹-HPiv)] _n , in which the repeating units are linked by bridging pyridone molecules. The reaction of cobalt nitrate hexahydrate with 2-hydroxy-6-methylpyridine (Hmhp) in the presence of the deprotonating agent (Et₃N) resulted in the crystallization of the 1D polymer of the composition [Li₂Co₇(μ₃-OH)₂(μ₃-Piv)₃(μ-Piv)₂(μ₃,η²-mhp)₅(μ,η²-mhp)₂(μ₃-mhp)(μ,η²-NO₃)·2MeCN] _n , in which the bulky metal fragments {Li₂Co₇(OH)₂(Piv)₅)(mhp)₈} are linked together through the lithium atoms by chelate bridging nitrate anions. The resulting 1D polymers were characterized by X-ray diffraction, and their magnetic properties were investigated.     

Pivalate Bridged High Spin Manganese(II) and Iron(II) Polymers

Antiferromagnetic Mn(II) polymers of general formula {[L₂Mn(μ-OOCCMe₃)₂][Mn₂(μ-OOCCMe₃)₄]}_n (L = 1,2-phenylenediamine (3) and 4,5-dimethyl-1,2-phenylenediamine (4)) were synthesized from [Mn(μ-OOCCMe₃)₂(HOEt)] _n (1) polymer and arenediamines in MeCN solution. The tetranuclear cluster Fe₄(μ₃-OH)₂(μ-OOCCMe₃)₄(η²-OOCCMe₃)₂(EtOH)₆ (5) was prepared by reacting FeSO₄·7H₂O with KOOCCMe₃ in EtOH and was used as starting pivalate iron(II) agent in further reactions. The thermolysis of 5 in MeCN was shown to result in a ferromagnetic polymer [Fe(μ-OOCCMe₃)₂] _n (6) containing tetrahedral iron(II) atoms. Cluster 5 was found to react with o-phenylenediamine giving rise to ferrimagnetic polymer [Fe(μ-OOCCMe₃)₂(HOEt)]_n (7). The reaction 7 with 2,6-diaminopyridine in MeCN results in binuclear antiferromagnetic complex (2,6-(NH₂)₂C₅H₃N)₂Fe₂(μ-OOCCMe₃)₄· 4MeCN (8). However the reaction of 4,5-dimethyl-1,2-phenylenediamine with polymer 7 yields a polymer {[L₂Fe(μ-OOCCMe₃)₂][Fe₂ (μ-OOCCMe₃)₄]} _n (9), which is an analogue of the manganese polymer 4. All newly synthesized compounds were characterized by the by X-ray diffraction studies and magnetic measurement. Dedicated to Professor Ilya I. Moiseev in recognition of his outstanding contribution to cluster chemistry     

Unsymmetrical dinuclear cobalt and nickel trimethylacetate complexes

The reaction of the dinuclear complex Co₂(-OOCCMe₃)₂(²-OOCCMe₃)₂bpy₂ (1) with the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x afforded the unsymmetrical dinuclear complex bpyCo₂(₂-O,²-OOCCMe₃)(₂-O,O"-OOCCMe₃)₂(²-OOCCMe₃) (2). The reaction of 2,2"-dipyridylamine with [Co(OH) _n (OOCCMe₃)_2–n ] _x gave rise to the analogous complex [(C₅H₄N)₂NH]Co₂(₂-O,²-OOCCMe₃)(-OOCCMe₃)₂(²-OOCCMe₃) (3). The reaction of complex 1 with Ni₄(₃-OH)₂(-OOCCMe₃)₄(OOCCMe₃)₂(MeCN)₂[²-o-C₆H₄(NH₂)(NHPh)]₂ (4) produced an isostructural heterometallic analog of complex 2 with composition bpyM₂(₂-O,²-OOCCMe₃)(₂-O,O"-OOCCMe₃)₂(²-OOCCMe₃) (5) (M = Co, Ni; Co : Ni = 1 : 1) and the dinuclear heterometallic complex bpy(HOOCCMe₃)M(-OH₂)(-OOCCMe₃)₂M(OOCCMe₃)₂[o-C₆H₄(NH₂)(NHPh)] (6) (M = Co, Ni; Co : Ni = 0.15 : 1.85). Compounds 2 and 5 exhibit ferromagnetic spin-spin exchange interactions.     

Formation of an Ni7(μ3-OH)6(η-OOCBu t )6(μ3-OOCBu t )2(Hdmpz)6 cluster during the thermolysis of binuclear complex Ni2(μ-OOCBu t )4(Hdmpz)2 (Hdmpz = 3,5-dimethylpyrazole)

Cluster Ni₇(μ₃-OH)₆(OOCBu ^t )₈(Hdmpz)₆ was found to form as a result of the thermal destruction of complex Ni₂(μ-OOCBu ^t )₄(Hdmpz)₂ at 190°C. The cluster was characterized using X-ray crystallography.     

Formation and Transformations of Polynuclear Hydroxo- and Oxotrimethylacetate Complexes of Ni(II) and Co(II)

Transformations of polymeric trimethylacetate complexes [M(OH) _n (OOCCMe₃)_{2 – n} ] _m (M = Ni (I) and Co (II)) and clusters Ni₉(₄-OH)₃(₃-OH)₃(-O,O-OOCCMe₃)(-O,O"-OOCCMe₃)₇(₃-O,O,O"-OOCCMe₃)₃(₄-O,O,O",O"-OOCCMe₃)(HOOCCMe₃)₄(III) and Co₆(₃-OH)₂(-OOCCMe₃)₁₀(HOOCCMe₃)₄(VIII), which are formed from Iand IIupon their recrystallization from nonpolar solvents, were studied. It was shown that the action of N-phenyl-o-phenylenediamine (L) on Ior IIIresults, depending on the solvent, in different tetranuclear clusters with the hydroxo bridges. For example, in benzene, the L₂Ni₄(₃-OH)₂(HOOCCMe₃)₄(-OOCCMe₃)₆complex (IX) is formed; its L molecules are coordinated in a monodentate way, whereas in acetonitrile, they chelate to give the {[o-C₆H₄(NH₂)(NHPh)]₂Ni₄(₃-OH)₂(MeCN)₂(OOCCMe₃)₂(-OOCCMe₃)₄} compound (X). Heating of Xin the presence of atmospheric oxygen yields IX, the mononuclear bissemiquinonediimine [o-C₆H₄(NH)(NPh)]₂Ni complex (XI), and water. It was noted that the use of aniline in these reactions affords, independent of the nature of the solvent, only one (NH₂C₆H₅)₂Ni₄(₃-OH)₂(HOOCCMe₃)₄(-OOCCMe₃)₆cluster (VI); in acetonitrile, this cluster is formed as the solvate VI· 2HOOCCMe₃(VIa). When treated with ethanol, Iand IIIgive the Ni₄(EtOH)₆(₃-OH)₂(₂-OOCCMe₃)₄(OOCCMe₃)₂cluster (V), which is structurally close to the known cobalt-containing analog IV. Thermolysis of IVin decalin at 170° causes its dimerization, giving the octanuclear Co₈(₄-O)₂( _n -OOCCMe₃)₁₂complex (VII) with the tetradentate oxo bridges.     

Magnetic properties of binuclear high-spin trimethylacetate nickel(II) complexes

The static magnetic susceptibility of mononuclear trimethylacetate nickel complex Ni(NH₂Ph)₄(OOCCMe₃)₂ (3) and binuclear complexes Ni₂(μ-OH₂)(μ-OOCCMe₃)₂(OOCCMe₃)₂(dipy)₂ (4) and Ni₂(μ-OOCCMe₃)₄py₂ (5) was measured in the temperature range of 2–300 K. The magnetic behavior of3 is typical of mononuclear complexes with the Ni¹¹ atom in the octahedral environment. Numerical calculations of the temperature dependence of magnetic susceptibility with inclusion of isotropic exchange interactions (J) and single-ion initial splitting parameters showed that the magnetic behavior of complexes4 and 5 can be interpreted in terms of ferromagnetic (for4) and antiferromagnetic (for5) interactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 437–442, March, 2000.     

Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3<Emphasis Type="Italic">s</Emphasis> and Co3<Emphasis Type="Italic">p</Emphasis> X-ray photoelectron spectroscopy

The electronic structure of mono-, hexa-, and nonanuclear cobalt trimethylacetate complexes was studied by XPS. The Co3s- and Co3p X-ray photoelectron spectra of the complexes were recorded. The Co3p spectrum of bivalent cobalt was calculated in the isolated-ion intermediate-coupling approximation. Spectrum analysis showed that the [Co(N-Phobsqdi)2(η′-N-Ph-opda)(OOCCMe₃)] complex is a strong-field complex with Co(III) in the diamagnetic state; the [Co(dipy)₂(OOCCMe₃)₂], [Co(dipyam)(OOCCMe₃)₂], and [Co₉(μ₃-OH)₆(μ-OOCCMe₃)₁₂(OCMe₂)₄] are high-spin weak-field Co(II) complexes; and the [Co₆(μ₄-O)₂(OOCCMe₃)₁₀(THF)₄] complex contains both the Co(II) and Co(III) atoms. The energy position of major Co3s- and Co3p spectral maxima were found to be sensitive to the nature of the nearest environment of cobalt atoms. The data correlate well with X-ray crystallographic data.     

Unusual coordination of a chloride ion to six copper ions: Synthesis and crystal structure of copper(II) complexes with 4-(4-hydroxyphenyl)-1,2,4-triazole

Novel copper(II) complexes, molecular [Cu₆(μ₆-Cl)(μ₃-OH)₂(μ-L)₆Cl₉(H₂O)₃] · 3H₂O (1) and polymeric [Cu(μ-L)(μ-OH)(H₂O)₂]Cl (2) (L = 4-(4-hydroxyphenyl)-1,2,4-triazole), have been prepared and characterized by X-ray structural analysis. Compound 1 appears to be an unusual example of a chloride ion with six equal Cu–Cl distances of 2.8397(3) Å. It has also been characterized by X-ray powder diffraction and magnetic measurements. Both complexes have distorted octahedral configurations of copper ions; the coordination cores are CuN₂Cl₂O₂ or CuN₂Cl₃O (1) and CuN₂O₄ (2).     

Reactions of ortho-Phenylenediamine with a Nickel Trimethylacetate Complex

Interaction of ortho-phenylenediamine with the nonanuclear nickel trimethylacetate cluster Ni₉(₄-OH)₃(₃-OH)₃( _n -OOCMe₃)₁₂(HOOCCMe₃)₄(I) in an amine deficiency yields the antiferromagnetic trinuclear complex [Ni₃{-N,N"-(NH₂)₂C₆H₄}₂(HCCOOCMe₃)₃(₃-OH)(-OOCCMe₃)₄]⁺(OOCCMe₃)^–(III) containing bridging diamine ligands. Reaction of excess diamine with Ior IIIleads to the formation of the paramagnetic monomer Ni{²-o-(NH₂)₂C₆H₄}₂(OOCCMe₃)₂(IV), which reacts with atmospheric oxygen to form the known bis(semiquinonediimine) complex Ni[1,2-(NH)₂C₆H₄]₂(V).     

Remarkable Anticancer Activity of Triruthenium-Arene Clusters Compared to Tetraruthenium-Arene Clusters

Abstract The in vitro activity of a series of ruthenium clusters, [(η⁶-C₆H₆)(η⁶-C₆Me₆)₂Ru₃(μ-H)₃(μ₃-O)][BF₄], [(η⁶-C₆H₆)(η⁶-1,4-ⁱPrC₆H₄Me)(η⁶-C₆Me₆)Ru₃(μ-H)₃(μ₃-O)][BF₄], [(η⁶-C₆H₆)₄Ru₄(μ-H)₄][BF₄]₂, [(η⁶-C₆H₅Me)₄Ru₄(μ-H)₄][BF₄]₂ and [(η⁶-C₆H₆)₄Ru₄(μ-H)₃(μ-OH)][Cl]₂, has been evaluated against A2780 and A2780cisR ovarian carcinoma cell lines. Both triruthenium clusters are very active compared to ruthenium compounds in general, whereas the tetraruthenium clusters do not display significant cytotoxicities. Since the triruthenium clusters are known to form supramolecular interactions with arenes and other functions, it is possible that such interactions are also important with respect to their mode of biological activity. The X-ray structure analysis of [(η⁶-C₆H₅Me)₄Ru₄(μ-H)₄][PF₆]₂ is also reported. Graphical Abstract The in vitro activity of a series of ruthenium clusters has been evaluated against A2780 and A2780cisR ovarian carcinoma cell lines and their activity compared to cisplatin. The triruthenium clusters are very active, while the tetraruthenium clusters do not display significant cytotoxicities. Dedicated to Professor Dieter Fenske on the occasion of his 65th birthday anniversary     

New Cyclosiloxanolate Cluster Complexes of Transition Metals

New cyclosiloxanolate transition metal cluster complex derivatives were prepared. PhSiO₂K reacted with NiX₂ (X₂ = Cl₂ or acac) to give K₂{[η⁶−(PhSiO₂)₆]₂[μ₃−(OH)]₂Ni₄K₄}, a mixed group 1–group 10 metal complex. PhSiO₂Na reacted with Ni(NH₃)₆I₂ to give Na{[η⁶−(PhSiO₂)₆]₂Ni₆(μ₆−I)} as the first example of “encapsulated” I⁻ ion in siloxanolate complexes. The macrocyclic Na₄{[η¹²−(PhSiO₂)₁₂]Cu₄} complex reacted with η⁶−(1,3,5−C₇H₈)Cr(CO)₃ to give the heterobimetallic adduct Na₄{[η¹²−(PhSiO₂)₁₂]Cu₄}· [Cr(CO)₃]₃ as one of the rare examples of heterobimetallic complexes with different oxidation numbers of the metals. The copper derivative {[η⁶−(PhSiO₂)₆]₂Cu₆(n−BuOH)₅} reacted in MeOH/CHCl₃ (1:6) with Et₄NCN to give the hexanuclear complex {[η⁶−(PhSiO₂)₆]₂Cu₆(η²−C₃H₅N₂O₂)₂}, containing 2-amino-2-oxoetanimidic acid methyl ester monoanion ligands, product of an unexpected C–C coupling reaction. This latter complex was characterized also by X-ray diffraction crystal and molecular structure determination. This paper is dedicated to the 70th birthday of Professor Dr. Gunter Schmid (Essen), pioneer of large cluster chemistry, known to friends as GOLD-Schmid, because of his famous discovery of the Au₅₅ cluster. The Authors are proud to be within his many friends.