Biological Potential of Halfsandwich Ruthenium(II) and Iridium (III) Complexes

In vitro studies with the ruthenium(II) and analogous iridium(III) complexes [Ru(η6- p-cymene)Cl2{Ph2PCH2CH2CH2S(O)xPh-κP}], [Ru(η6-p-cymene)Cl{Ph2PCH2CH2CH2S(O)xPh- κP,κS}][PF6] (1-4), [Ir(η5-C5Me5)Cl2{Ph2PCH2CH2CH2S(O)xPh-κP}] and [Ir(η5-C5Me5)Cl{Ph2 PCH2CH2CH2S(O)xPh-κP,κS}][PF6] (5-8; x = 0, 1) revealed the high selectivity toward the 8505C, A253, MCF-7, SW480 and 518A2 cancer cell lines. Thus, the cationic ruthenium complex 4 proved to be the most selective one. In case of the neutral and cationic ruthenium complexes 1-4 the caspase-dependent apoptotic cell death was proven as the main cause of the drug's tumoricidal action on 8505C cell line.

The challenge of deciphering linkage isomers in mixtures of oligomeric complexes derived from 9-methyladenine and trans-(NH3)2Pt(II) units

Metal coordination to N9-substituted adenines, such as the model nucleobase 9-methyladenine (9MeA), under neutral or weakly acidic pH conditions in water preferably occurs at N1 and/or N7. This leads, not only to mononuclear linkage isomers with N1 or N7 binding, but also to species that involve both N1 and N7 metal binding in the form of dinuclear or oligomeric species. Application of a trans-(NH3)2Pt(II) unit and restriction of metal coordination to the N1 and N7 sites and the size of the oligomer to four metal entities generates over 50 possible isomers, which display different feasible connectivities. Slowly interconverting rotamers are not included in this number. Based on (1)H NMR spectroscopic analysis, a qualitative assessment of the spectroscopic features of N1,N7-bridged species was attempted. By studying the solution behavior of selected isolated and structurally characterized compounds, such as trans-[PtCl(9MeA-N7)(NH3)2]ClO4⋅2H2O or trans,trans-[{PtCl(NH3)2}2(9MeA-N1,N7)][ClO4]2⋅H2O, and also by application of a 9MeA complex with an (NH3)3Pt(II) entity at N7, [Pt(9MeA-N7)(NH3)3][NO3]2, which blocks further cross-link formation at the N7 site, basic NMR spectroscopic signatures of N1,N7-bridged Pt(II) complexes were identified. Among others, the trinuclear complex trans-[Pt(NH3)2{μ-(N1-9MeA-N7)Pt(NH3)3}2][ClO4]6⋅2H2O was crystallized and its rotational isomerism in aqueous solution was studied by NMR spectroscopy and DFT calculations. Interestingly, simultaneous Pt(II) coordination to N1 and N7 acidifies the exocyclic amino group of the two 9MeA ligands sufficiently to permit replacement of one proton each by a bridging heterometal ion, Hg(II) or Cu(II), under mild conditions in water.

Lithiated sulfoxides: α-sulfinyl functionalized carbanions

Lithiated sulfoxides of the type [Li₂{CRR′S(O)Ar}₂(TMEDA)₂], their molecular structures, and diastereoselective C–C bond formation reactions with benzaldehyde and benzophenone are presented.

Synthese und Charakterisierung von kronenetherstabilisierten Platin(IV)- Komplexen mit Aminosäureliganden / Synthesis and Characterization of Amino Acid Complexes of Platinum(IV) Stabilized by Crown Ethers

Crown ether complexed pentachloro(aqua)platinic acid, (H3O)[PtCl5(H2O)]·2(18-cr-6)·6H2O (1) reacts with glycine, L-alanine, and DL-2-aminobutyric acid to give cis-[PtCl4(O-glyH)(H2O)]·(18-cr-6)·H2O (4a)1 and cis-[PtCl4(O-amacH)(H2O)]·(18-cr-6) (amacH = alaH 4b, abuH 4c), respectively, as well as (amacH2)2[PtCl6]·2(18-cr-6) (amacH = glyH 5a, alaH 5b, abuH 5c). The crown ether complexed hexachloroplatinic acid, (H3O) 2[PtCl6]·2(18-cr-6) (2), reacts with glycine to afford (glyH2)[PtCl4(N,O-gly)]·2(18-cr-6)·1.25H2O (6).

The structures of 4b and 6 were determined by X-ray diffraction. The alanine ligand in 4b is a zwitterion that is coordinated to platinum by one oxygen atom of the carboxylate group only. The other oxygen atom is engaged in a strong hydrogen bond to the ds-coordinated aqua ligand. The glycinato ligand in 6 is N, O-coordinated at platinum forming an anion [PtCl4(N,O-gly)]- . The other oxygen atom of the carboxylate group is involved in a strong hydrogen bridge to the cation (glyH2)+. In both complexes hydrogen bridges are formed between the -N+H3 and -NH2 groups of the amino acid ligands and the oxygen atoms of the crown ether molecules.

Organotin(IV)-loaded mesoporous silica as a biocompatible strategy in cancer treatment

The strong therapeutic potential of an organotin(IV) compound loaded in nanostructured silica (SBA-15pSn) is demonstrated: B16 melanoma tumor growth in syngeneic C57BL/6 mice is almost completely abolished. In contrast to apoptosis as the basic mechanism of the anticancer action of numerous chemotherapeutics, the important advantage of this SBA-15pSn mesoporous material is the induction of cell differentiation, an effect unknown for metal-based drugs and nanomaterials alone. This non-aggressive mode of drug action is highly efficient against cancer cells but is in the concentration range used nontoxic for normal tissue. JNK (Jun-amino-terminal kinase)-independent apoptosis accompanied by the development of the melanocyte-like nonproliferative phenotype of survived cells indicates the extraordinary potential of SBA-15pSn to suppress tumor growth without undesirable compensatory proliferation of malignant cells in response to neighboring cell death.

Anticancer potential of (pentamethylcyclopentadienyl)chloridoiridium(III) complexes bearing κP and κP,κS-coordinated Ph2 PCH2 CH2 CH2 S(O)x Ph (x=0-2) ligands

Iridium(III) complexes of the type [Ir(η(5) -C5 Me5 )Cl2 {Ph2 PCH2 CH2 CH2 S(O)x Ph-κP}] (x=0-2; 1-3) and [Ir(η(5) -C5 Me5 )Cl{Ph2 PCH2 CH2 CH2 S(O)x Ph-κP,κS}][PF6 ] (x=0-1; 4 and 5) with 3-(diphenylphosphino)propyl phenyl sulfide, sulfoxide, and sulfone ligands Ph2 PCH2 CH2 CH2 S(O)x Ph were designed, synthesized, and characterized fully, including X-ray diffraction analyses for complexes 3 and 4. In vitro studies against human thyroid carcinoma (8505C), submandibular carcinoma (A253), breast adenocarcinoma (MCF-7), colon adenocarcinoma (SW480), and melanoma (518A2) cell lines provided evidence for the high biological potential of the neutral and cationic iridium(III) complexes. Neutral iridium(III) complex 5 proved to be the most active, with IC50 values up to about 0.1 μM, representing activities of up to one order of magnitude higher than cisplatin. Using 8505C cells, apoptosis was shown to be the main mechanism through which complex 5 exerts its tumoricidal action. The described iridium(III) complexes represent potential leads in the search for novel metal-based anticancer agents.

Biological activity of neutral and cationic iridium(III) complexes with κP and κP,κS coordinated Ph₂PCH₂S(O)xPh (x = 0-2) ligands

Neutral iridium(III) complexes of the type [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)xPh-κP}] (1-3) with diphenylphosphino-functionalized methyl phenyl sulfides, sulfoxides, and sulfones Ph₂PCH₂S(O)xPh (x = 0, L1; 1, L2; 2, L3) and the cationic complex [Ir(η(5)-C₅Me₅)Cl{Ph₂PCH₂SPh-κP,κS}][PF6] (4) were synthesized and fully characterized analytically and spectroscopically. Furthermore, the structure of 2 was determined by X-ray diffraction analysis. The biological potential of the neutral and cationic iridium(III) complexes was tested in vitro against the cell lines 8505C, A253, MCF-7, SW480 and 518A2. Complex [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)Ph-κP}] (2), with ligand L2 κP coordinated containing a pendent sulfinyl group, is the most active one (IC₅₀ values of about 3 μM), thus, with activities comparable to cisplatin. Complex 2 proved to have an even a higher antiproliferative activity than cisplatin against 8505C and SW480 cell lines, used as a model system of highly anaplastic cancers with low sensitivity to conventional chemotherapeutics such as cisplatin. Additional experiments demonstrated that apoptosis and autophagic cell death contribute to the drug's tumoricidal action.

On the isomerization of cyclooctyne into cycloocta-1,3-diene: synthesis, characterization and structure of a dinuclear platinum(II) complex with a μ-η2:η2-1,3-COD ligand

The Zeise's salt type cyclooctyne compound [K(18C6)][PtCl(3)(COC)] (1; COC = cyclooctyne; 18C6 = 18-crown-6) was found to react in chloroform solution at room temperature within several weeks yielding the dinuclear cyclooctadiene compound [K(18C6)](2)[(PtCl(3))(2)(μ-η(2):η(2)-1,3-COD)] (2; 1,3-COD = cycloocta-1,3-diene) and non-coordinated cycloocta-1,3-diene. The identity of 2 was confirmed by microanalysis, NMR spectroscopy ((1)H, (13)C) and electrospray ionization mass spectrometry (ESI-MS). A single-crystal X-ray diffraction analysis of 2 exhibited a bridging μ-η(2):η(2)-cycloocta-1,3-diene ligand with non-conjugated double bonds each coordinated to a PtCl(3) fragment. On the basis of DFT calculations as well as energy decomposition analyses (EDA), charge decomposition analyses (CDA) and natural bond orbital (NBO) analyses the peculiarities of the nature of the Pt-C bonds in the dinuclear complex anion [(PtCl(3))(2)(μ-η(2):η(2)-1,3-COD)](2-) (2a') compared with those in mononuclear olefin complexes of Zeise's salt type [PtCl(3)L](-) (L = η(2)-1,3-COD, 3a'; cis-but-2-ene, 4a'; COE, 5a'; COE = cyclooctene) are discussed. Furthermore, the driving force for the strongly exergonic reaction with formation of the cyclooctadiene complex 2a' was found to be a significant release of ring strain of the cyclooctyne ligand in the starting compound 1.

Chlorido[1-diphenyl-phosphanyl-3-(phenyl-sulfan-yl)propane-κ(2)P,S](η(5)-penta-methyl-cyclo-penta-dien-yl)iridium(III) chloride monohydrate

The crystal structure of the title compound, [Ir(C₁₀H₁₅)Cl(C₂₁H₂₁PS)]Cl·H₂O, consists of discrete [Ir(η⁵-C₅Me₅)Cl{Ph₂P(CH₂)₃SPh-κP,κS}]⁺ cations, chloride anions and water mol­ecules. The Ir^III atom is coordinated by an η⁵-C₅Me₅ ligand, a chloride and a Ph₂P(CH₂)₃SPh-κP,κS ligand, leading to a three-legged piano-stool geometry. In the crystal, two water molecules and two chloride anions are linked by weak O—H⋯Cl hydrogen bonding into tetra­mers that are located on centers of inversion. The H atoms of one of the methyl groups are disordered and were refined using a split model.

[3-Methoxy-1-(phenylsulfanyl)propyl]triphenyltin(IV) benzene 0.17-solvate

In the title compound, [Sn(C₆H₅)₃(C₁₀H₁₃OS)]·0.17C₆H₆, the Sn^IV atom exhibits a slightly distorted tetra­hedral coordination geometry built up by four C atoms, which are the three ipso-C atoms of the phenyl rings and the α-C atom of the deprotonated γ-O-functionalized propyl phenyl sulfide. The benzene mol­ecule lies about a threefold rotoinversion axis.

(OC-6-33)-(2,2'-Bipyridine-κN,N')trimeth-yl(2-methyl-sulfanyl-2-thia-zoline-κN)platinum(IV) tetra-fluoridoborate

The asymmetric unit of the title complex, [Pt(CH(3))(3)(C(10)H(8)N(2))(C(4)H(7)NS(2))]BF(4), contains two crystallographically independent mol-ecules. The Pt(IV) atom in each complex cation exhibits a distorted octa-hedral coordination geometry, built up by three methyl ligands in a facial binding fashion, a bipyridine ligand and a monodentately N-bound 2-methyl-sulfanyl-2-thia-zoline ligand (configuration index: OC-6-33). In the crystal structure, weak inter-molecular C-H⋯F hydrogen bonds are found between the complex cations and BF(4) (-) anions.

Synthesis, characterization and reactivity of carbohydrate platinum(IV) complexes with thioglycoside ligands

Reactions of fac-[PtMe3(4,4'-R2bpy)(Me2CO)][BF4] (R = H, 1a; tBu, 1b) and fac-[PtMe3(OAc-kappa2O,O')(Me2CO)] (2), respectively, with thioglycosides containing thioethyl (ch-SEt) and thioimidate (ch-STaz, Taz = thiazoline-2-yl) anomeric groups led to the formation of the carbohydrate platinum(IV) complexes fac-[PtMe3(4,4-R2bpy)(ch*)][BF4] (ch* = ch-SEt, 8-14; ch-STaz, 15-23) and fac-[PtMe3(OAc-kappa2O,O')(ch*)] (ch* = ch-SEt, 24-28; ch-STaz = 29-35), respectively. NMR (1H, 13C, 195Pt) spectroscopic investigations and a single-crystal X-ray diffraction analysis of 19 (ch-STaz = 2-thiazolinyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-galactopyranose) revealed the S coordination of the ch-SEt glycosides and the N coordination of the ch-STaz glycosides. Furthermore, X-ray structure analyses of the two decomposition products fac-[PtMe3(bpy)(STazH-kappaS)][BF4] (21a) and 1,6-anhydro-2,3,4-tri-O-benzoyl-beta-D-glucopyranose (23a), where a cleavage of the anomeric C-S bond had occurred in both cases, gave rise to the assumption that this decomposition was mediated due to coordination of the thioglycosides to the high electrophilic platinum(IV) atom, in non-strictly dried solutions. Reactions of fac-[PtMe3(Me2CO)3][BF4] (3) with ch-SEt as well as with ch-SPT and ch-Sbpy thioglycosides (PT = 4-(pyridine-2-yl)-thiazole-2-yl; bpy = 2,2'-bipyridine-6-yl), having N,S and N,N heteroaryl anomeric groups, respectively, led to the formation of platinum(IV) complexes of the type fac-[PtMe3(ch*)][BF4] (ch* = ch-SEt, 36-40, ch-SPT 42-44, ch-Sbpy 45, 46). The thioglycosides were found to be coordinated in a tridentate kappaS,kappa2O,O, kappaS,kappaN,kappaO and kappaS,kappa2N,N coordination mode, respectively. Analogous reactions with ch-STaz ligands succeeded for 2-thiazolinyl 2,3,4-tri-O-benzyl-6-O-(2,2'-bipyridine-6-yl)-1-thio-beta-D-glucopyranoside (5h) resulting in fac-[PtMe3(ch-STaz)][BF4] (41, ch-STaz = 5h), having a kappa3N,N',N''coordinated thioglycoside ligand.

Synthesis, characterization and structures of cyclic organorhodium complexes of the type [Rh{CH(SO₂Ph)CH₂CH₂YR₂-κC,κY}L₂] (YR₂ = PPh₂, NMe₂; L₂ = diphosphine, cyclooctadiene)

Reactions of dinuclear chloridorhodium(I) complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = P[symbol: see text]P: Me₂P(CH₂)₂PMe₂, dmpe, 7a; Ph₂PCH₂PPh₂, dppm, 7b; Ph₂P(CH₂)₂PPh₂, dppe, 7c; Ph₂P(CH₂)₃PPh₂, dppp, 7d; L₂ = cycloocta-1,5-diene, cod, 5) with lithiated γ-phosphino- and γ-aminofunctionalized propyl phenyl sulfones (Li[CH(SO₂Ph)CH₂CH₂PPh₂], 2; Li[CH(SO₂Ph)CH₂CH₂NMe₂], 4) led to the formation of organorhodium inner complexes of the type [Rh{CH(SO₂Ph)CH₂CH₂PPh₂-κC,κP}(P[symbol: see text]P)] (8a-d), [Rh{CH(SO₂Ph)CH₂CH₂NMe₂-κC,κN}(P[symbol: see text]P)] (9a-d), [Rh{CH(SO₂Ph)CH₂CH₂PPh₂-κC,κP}(cod)]·LiCl (11·LiCl) and [Rh{CH(SO₂Ph)CH₂CH₂NMe₂-κC,κN}(cod)]·LiCl (12·LiCl), respectively. Single-crystal X-ray diffraction analysis of 9c·THF, 11 and 12 exhibited in all three compounds a distorted square planar coordination of the rhodium atoms having bidentately coordinated neutral co-ligands (cod, 11, 12; dppe, 9c) and anionic α-phenylsulfonyl γ-phosphinopropyl (κC,κP; 11) and γ-aminopropyl ligands (κC,κN; 12, 9c), thus being typical organorhodium inner complexes. Furthermore, organorhodium inner complexes of type 8 were obtained in reactions of the dinuclear chloridobridged rhodium complexes [(RhL₂)₂(μ-Cl)₂] (L₂ = P[symbol: see text]P, 7a-d; cod, 5; (C₂H₄)₂, 6) with the (non-lithiated) γ-phosphinofunctionalized propyl phenyl sulfone PhSO₂CH₂CH₂CH₂PPh₂ (1) resulting in the formation of complexes having the sulfone κP coordinated ([RhClL₂-(Ph₂PCH₂CH₂CH₂SO₂Ph-κP)] (L₂ = P[symbol: see text]P, 10a-d; cod, 13; (C₂H₄)₂, 14) which were deprotonated (10a-d, 13) at the α-C atom with lithium diisopropyl amide (LDA) in a subsequent reaction. Single-crystal X-ray diffraction analysis of 10c (P[symbol: see text]P = dppe) revealed the expected square-planar coordination geometry of Rh. The identities of all rhodium complexes have been unambiguously proved by microanalyses and NMR spectroscopy (¹H, ¹³C, ³¹P).

Structural and Computational Studies of 1-Methyl-2-thiocytosine and its Coordination Mode in a Dinuclear Platinum(IV) Complex [(PtMe3)2(μ-1-MeSCy-1κN3,1:2κ2S)2][BF4]2

X-Ray diffraction analysis of 1-methyl-2-thiocytosine (1-MeSCy, 1) revealed that its crystals contain two structurally very similar independent molecules (A, B). These molecules are connected through a complex network of hydrogen bonds. Centrosymmetric di- and tetrameric units AAʹ and BAAʹBʹ, respectively, are formed through N-H...N hydrogen bonds (N4a...N3aʹ 3.019(4) Å , AAʹ; N4a...N3b 2.988(4) Å, BAAʹBʹ), and the tetrameric units are connected through N-H...S hydrogen bonds. The arrangement of A and B molecules found in crystals of 1 was confirmed by DFT calculations up to tetrameric BAAʹBʹ units, yielding similar equilibrium structures, and the energies of the N-H...N hydrogen bonds between A and Aʹ and A and B were calculated to be about 10 kcal mol−1. Reaction of 1-MeSCy (1) with [PtMe3(Me2CO)3][BF4] (2) led to the formation of the ionic dinuclear complex [(PtMe3)2(μ-1-MeSCy-1κN3,1:2κ2S)2][BF4]2 (3) which was fully characterized by NMR (1H, 13C, 195Pt) and IR spectroscopy, ESI mass spectrometry and microanalysis. A singlecrystal X-ray diffraction analysis of 3 confirmed the dinuclear structure of the complex. The complex cation consists of a central [Pt2(μ-S)2] core having bound the 1-methyl-2-thiocytosine ligands in a 1κN3,1:2κ2S coordination mode in a face-to-face arrangement, the thionucleobase ligands being present as the amino-thione tautomer.

(Acetato-κO)(2,2'-bipyridine-κN,N')trimethyl-platinum(IV) monohydrate

In the title hydrate, [Pt(CH(3))(3)(CH(3)COO)(C(10)H(8)N(2))]·H(2)O, the Pt(IV) atom exhibits a distorted octa-hedral coordination geometry built up by three methyl ligands in a facial arrangement, a bipyridine ligand and a monodentately bound acetate ligand. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds are observed between the water mol-ecule and the platinum complex, which link the mol-ecules into chains along the c axis.