Syntheses and characterization of mono and dinuclear complexes of platinum group metals bearing benzene-linked bis(pyrazolyl)methane ligands

Reaction of the benzene-linked bis(pyrazolyl)methane ligands, 1,4-bis{bis(pyrazolyl)-methyl}benzene (L1) and 1,4-bis{bis(3-methylpyrazolyl)methyl}benzene (L2), with pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh and Ir) in the presence of NH₄PF₆ results under stoichiometric control in both, mono and dinuclear complexes, [(η⁵-C₅Me₅)RhCl(L)]⁺ {L = L1 (1); L2 (2)}, [(η⁵-C₅Me₅)IrCl(L)]⁺ {L = L1 (3); L2 (4)} and [{(η⁵-C₅Me₅)RhCl}₂(μ-L)]²⁺ {L = L1 (5); L2 (6)}, [{(η⁵-C₅Me₅)IrCl}₂(μ-L)]²⁺ {L = L1 (7); L2 (8)}. In contrast, reaction of arene ruthenium complexes [(η⁶­arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆) with the same ligands (L1 or L2) gives only the dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(μ-L)]²⁺ {L = L1 (9); L2 (10)}, [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(μ-L)]²⁺ {L = L1 (11); L2 (12)} and [{(η⁶-C₆Me₆)RuCl}₂(μ-L)]²⁺ {L = L1 (13); L2 (14)}. All complexes were isolated as their hexafluorophosphate salts. The single-crystal X-ray crystal structure analyses of [7](PF₆)₂, [9](PF₆)₂ and [11](PF₆)₂ reveal a typical piano-stool geometry around the metal centers with six-membered metallo-cycle in which the 1,4-bis{bis(pyrazolyl)-methyl}benzene acts as a bis-bidentate chelating ligand.     

Syntheses and characterization of [(η-C6Me6)Ru(μ-N3)(X)]2 (X = N3 and Cl) complexes and their reactions towards mono- and bidentate ligands

The reaction of the complex [{(η⁶-C₆Me₆)Ru(μ-Cl)Cl}₂] 1 with sodium azide ligand gave two new dimers of the composition [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2 and [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3, depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. These complexes undergo substitution reactions with monodentate ligands to yield monomeric complexes of the type [(η⁶-C₆Me₆)Ru(X)(N₃)(L)] {X = N₃, Cl, L = PPh₃ (4a, 9a); PMe₂Ph (4b, 9b); AsPh₃ (4c, 9c); X = N₃, L = pyrazole (Hpz) (5a); 3-methylpyrazole (3-Hmpz) (5b) and 3,5-dimethyl-pyrazole (3,5-Hdmpz) (5c)}. Complexes 2 and 3 also react with bidentate ligands to give bridging complexes of the type [{(η⁶-C₆Me₆)Ru(N₃)(X)]₂(μ-L)} {X = N₃, Cl, L = 1,2-bis(diphenylphosphino)methane (dppm) (6, 10); 1,2-bis(diphenylphosphino)ethane (dppe) (7, 11); 1,2-bis(diphenylphosphino)propane (dppp) (8, 12); X = Cl, L = 4,4-bipyridine (4,4′-bipy) (13)}. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as by analytical data.The molecular structures of the representative complexes [{(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)}₂] 2, [{(η⁶-C₆Me₆)Ru(μ-N₃)Cl}₂] 3,[(η⁶-C₆Me₆)Ru(N₃)₂(PPh₃)] 4a and [{(η⁶-C₆Me₆)Ru(N₃)₂}₂ (μ-dppm)] 6 were established by single crystal X-ray diffraction studies.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

Cytotoxic half-sandwich rhodium(III) complexes: Polypyridyl ligand influence on their DNA binding properties and cellular uptake

The DNA binding of polypyridyl (pp) (η⁵-C₅Me₅)Rh^III complexes of the types [(η⁵-C₅Me₅)RhCl(pp)](CF₃SO₃) (2-6) (pp = bpy, phen, dpq, dppz, dppn), [(η⁵-C₅Me₅)Rh{(Me₂N)₂CS}(pp)](CF₃SO₃)₂ (7-9) (pp = dpq, dppz, dppn) and [(η⁵-C₅Me₅)Rh(L)(pp)](CF₃SO₃) (10) (L = C₆H₅S⁻) and (11) (L = C₁₀H₇S⁻) has been studied by UV/Vis spectroscopy, circular dichroismus and viscosity measurements. Complexes 3-11 are cytotoxic towards the human MCF-7 breast and HT-29 colon cancer cell lines and exhibit IC₅₀ values in the range 0.56-10.7 μM. Stable intercalative binding into CT-DNA is indicated for the dpq and dppz complexes by large increases ΔT_m of 6-12 °C in the DNA thermal denaturation temperature for r = [complex]/[DNA] = 0.1 and by induced CD bands and large viscosity increases. In contrast, significant DNA lengthening is not observed after incubation of the biopolymer with the dppn complexes 2 and 9 at molar ratios of r < 0.08. Pronounced hypochromic shifts for the π-π^∗ transitions of the dppn ligands in the range 320-425 nm indicate the possible presence of surface stacking. The in vitro cytotoxicities of the chloro complexes 4-6 and the (Me₂N)₂CS complexes 7-9 are dependent on the size of the polypyridyl ligand with IC₅₀ values decreasing in the order dpq > dppz > dppn. For instance, IC₅₀ values of 5.3, 1.5 and 0.91 μM were determined for 7-9 against MCF-7 cells. Rapid Cl⁻/H₂O exchange leads the formation of aqua dications for 4-6, whose levels of cellular uptake and cytotoxicities are similar to those established for 7-9. Intramolecular interactions between the aromatic thiolate and dppz ligands of 10 and 11 prevent significant DNA intercalation. X-ray structural determinations have been performed for 2-7 and 11.     

Synthesis, characterization and molecular structure of the [(η-C6Me6)Ru(μ-N3)(N3)]2 complex and its reactions with some monodentate ligands

The reaction of complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂ (1) with sodium azide yielded complexes of the composition [(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)]₂ (2) and [(η⁶-C₆Me₆)Ru(μ-N₃)(Cl)]₂ (3), depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. Complexes 2 and 3 undergo substitution reactions with monodentate ligands such as PPh₃, PMe₂Ph and AsPh₃ to yield monomeric complexes. The structure of complex 2 was determined by X-ray crystallography. All these complexes were characterized by micro analytical data and by FT-IR and FT-NMR spectroscopy. Complex 2 crystallizes in the monoclinic space group P2₁/n with a = 8.5370(11) Å, b = 16.192(2) Å, c = 10.4535(13) Å and β = 110.877(2)°.     

(1,2,3,4,7-Pentamethylindenyl)rhodium complexes with arene ligands

The reaction of (η⁵-C₉H₂Me₅)Rh(1,5-C₈H₁₂) (1) with I₂ gives the iodide complex [(η⁵-C₉H₂Me₅)RhI₂]₂ (2). The solvate complex [(η⁵- C₉H₂Me₅)Rh(MeNO₂)₃]²⁺ (generated in situ by treatment of 2 with Ag⁺ in nitromethane) reacts with benzene and its derivatives giving the dicationic arene complexes [(η⁵-₉H₂Me₅)Rh(arene)]²⁺ [arene = C₆H₆ (3a), C₆Me₆ (3b), C₆H₅OMe (3c)]. Similar reaction with the borole sandwich compound CpRh(η⁵-C₄H₄BPh) results in the arene-type complex [CpRh(μ-η⁵:η⁶-C₄H₄BPh)Rh(η⁵-C₉H₂Me₅)]²⁺ (4). Treatment of 2 with CpTl in acetonitrile affords cation [(η⁵-C₉H₂Me₅)RhCp]⁺ (5). The structure of [3c](BF₄)₂ was determined by X-ray diffraction. The electrochemical behaviour of complexes prepared was studied. The rhodium-benzene bonding in series of the related complexes [(ring)Rh(C₆H₆)]²⁺ (ring = Cp, Cp^∗, C₉H₇, C₉H₂Me₅) was analyzed using energy and charge decomposition schemes.     

Homolysis of the Ln-N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with 2-pyridylmethyl and 3-pyridylmethyl-functionalized indenyl ligands

Two series of new organolanthanide(II) complexes with general formula {η⁵:η¹-[1-R-3-(2-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (3), Eu (4); R = Me₃Si-, Ln = Yb (5), Eu (6)), and {η⁵:η¹-[1-R-3-(3-C₅H₄NCH₂)C₉H₅]}₂Ln(II) (R = H-, Ln = Yb (9), Eu (10); R = Me₃Si-, Ln = Yb (11), Eu (12)) were synthesized by silylamine elimination with one-electron reductive reactions of lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) with 2 equiv. 1-R-3-(2-C₅H₄NCH₂)C₉H₆ (R = H (1), Me₃Si- (2)) or 1-R-3-(3-C₅H₄NCH₂)C₉H₆ (R = H (7), Me₃Si- (8)) in good yields. All the complexes were fully characterized by elemental analyses and spectroscopic methods. Complexes 3 and 5 were additionally characterized by single-crystal X-ray diffraction study. The catalytic activities of the complexes for MMA polymerization were examined. It was found that complexes with 3-pyridylmethyl substituent on the indenyl ligands could function as single-component MMA polymerization catalysts with good activities, while the complexes with 2-pyridylmethyl substituent on the indenyl ligands cannot catalyze MMA polymerization. The temperatures and solvents effect on the MMA polymerization have also been examined.     

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

The allyl-substituted group 4 metal complexes [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti, R = CH₂CHCH₂, (2); R = CH₂C(CH₃)CH₂ (3); M = Zr, R = CH₂CHCH₂ (4), R = CH₂C(CH₃)CH₂ (5)] have been synthesized by the reaction of allyl ansa-magnesocene derivatives and the tetrachloride salts of the corresponding transition metal. The dialkyl complexes ] [M = Ti, R = CH₂=CHCH₂, R′ = Me (6), R′ = CH₂Ph (7); R = CH₂C(CH₃)CH₂, R′ = Me (8), R′ = CH₂Ph (9); M = Zr, R = CH₂CHCH₂, R′ = Me (10), R′ = CH₂Ph (11); R = CH₂C(CH₃)CH₂, R′ = Me (12), R′ = CH₂Ph (13)] have been synthesized by the reaction of the corresponding ansa-metallocene dichloride complexes 2-5 and two molar equivalents of the alkyl Grignard reagent. Compounds 2-5 reacted with H₂ under catalytic conditions (Wilkinson’s catalyst or Pd/C) to give the hydrogenation products [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = CH₂CH₂CH₃ (14) or R = CH₂CH(CH₃)₂ (15); M = Zr and R = CH₂CH₂CH₃ (16) or R = CH₂CH(CH₃)₂ (17)]. The reactivity of 2-5 has also been tested in hydroboration and hydrosilylation reactions. The hydroboration reactions of 3, 4 and 5 with 9-borabicyclo[3.3.1]nonane (9-BBN) yielded the complexes [M{(9-BBN)CH₂CH(R)CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (18); M = Zr and R = H (19) or R = CH₃ (20)]. The reaction with the silane reagents HSiMe₂Cl gave the corresponding [M{ClMe₂SiCH₂CHRCH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (21); M = Zr and R = H (22) or R = CH₃ (23)]. The reaction of 22 with t-BuMe₂SiOH produced a new complex [Zr{t-BuMe₂SiOSi(Me₂)CH₂CH₂CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (24) through the formation of Si-O-Si bonds. On the other hand, reactivity studies of some zirconocene complexes were carried out, with the insertion reaction of phenyl isocyanate (PhNCO) into the zirconium-carbon σ-bond of [Zr{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}₂Me₂] (25) giving [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr{Me{κ²-O,N-OC(Me)NPh}] as a mixture of two isomers 26a-b. The reaction of [Zr{(n-Bu)(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CH₂Ph)₂] (27) with CO also provided a mixture of two isomers [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr(CH₂Ph){κ²-O,C-COCH₂Ph}] 28a-b. The molecular structures of 4, 11, 16 and 17 have been determined by single-crystal X-ray diffraction studies.     

Syntheses and characterization of η-hexamethylbenzeneruthenium(II)-β-diketone complexes: their reactions with mono- and bidentate neutral ligands

The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂1 react with sodium salts of β-diketonato ligands in methanol to afford the oxygen bonded neutral complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)Cl] {R¹, R² = CH₃ (2), CH₃, C₆H₅ (3), C₆H₅ (4), OCH₃ (5), OC₂H₅ (6)}. Complex 4 with AgBF₄ yields the γ-carbon bonded ruthenium dimeric complex 7. Complex 4 also reacts with tertiary phosphines and bridging ligands to yield complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)(L)]⁺ (L = PPh₃ (8), PMe₂Ph (9)) and [{η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)}₂(μ-L)] L = 4,4′-bipyridine (4,4′-bipy) (11), 1,4-dicyanobenzene (DCB) (12) and pyrazine (Pz) (13). Complexes 2-4 react with sodium azide to yield neutral complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)N₃] {R¹, R² = CH₃ (10a), CH₃, C₆H₅ (10b), C₆H₅ (10c). All these complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures of complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′CH₃COCH-COC₆H₅)Cl] (3) and [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅] (4) were established by single crystal X-ray diffraction studies. The complex 3 crystallizes in the triclinic space group, [a = 7.9517(4), b = 9.0582(4) and c = 14.2373(8) Å, α = 88.442(3)°, β = 76.6.8(3)° and γ = 81.715(3)°. V = 987.17(9) ų, Z = 2]. Complex 4 crystallizes in the monoclinic space group, P2₁/c [a = 7.5894(8), b = 20.708(2) and c = 29.208(3) Å,β = 92.059(3)° V = 4587.5(9) ų, Z = 8].     

Synthesis and structure of isopropyldimethylsilyl-substituted octamethyltitanocene

Reduction of isopropyldimethylsilyl-substituted titanocene dichloride [TiCl₂(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (1) by excess magnesium in the presence of excess bis(trimethylsilyl)ethyne (btmse) in tetrahydrofuran at 60 °C yielded a mixture of products amongst them only the trinuclear Ti-Mg-Ti hydrido-bridged complex Mg[Ti(μ-H)₂(η⁵-C₅Me₄SiMe₂Prⁱ)]₂ (3) was isolated and characterized. The precursor of titanocene, [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂(η²-btmse)] (6), was obtained from the identical system which, after initial formation of [TiCl(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (2), reacted at −18 °C overnight and then the solution was rapidly separated from the remaining magnesium. Titanocene [Ti(η⁵-C₅Me₄SiMe₂Prⁱ)₂] (7) was obtained by thermolysis of 6 at 75 °C in vacuum. Crystal structures of 1, 2, 3, 6, and 7 were determined.     

Synthesis of new chloro methyl niobium and tantalum complexes with silyl-cyclopentadienyl ligands: X-ray crystal structure of [Ta{η-C5H3(SiMe3)2}Cl2Me2]

Trichloro methyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₃Me] (X = Cl, 2; Me, 3), dichloro dimethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₂Me₂] (X = Cl, 4; Me, 5) and tetramethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Me₄] (X = Me, 6; Cl, 7) niobium complexes were synthesized by treatment of starting tetrachloro derivatives [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1a; Me, 1b) with dimethyl zinc or chloro methyl magnesium in different proportions and conditions. A mixture of trichloro methyl and dichloro dimethyl tantalum complexes [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl_4−xMe_x] (x = 1, 8; 2, 9) in a 2:1 molar ratio was obtained in the reaction of [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl₄] (1c) with 0.5 equivalents of ZnMe₂ in toluene at low temperature. 8 could be isolated as single compound when 1 equivalent of 1c was added to the mixtures of 8 and 9, while the reaction of 1c with 1.5 equivalents of dimethyl zinc gave 9 as unitary product. However, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 0.5 equivalents of alkylating reagent giving the trichloro methyl compound [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₃Me] (10) in good yield. On the other hand, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 2 equivalents of MgClMe in hexane at room temperature giving a mixture of dichloro dimethyl and chloro trimethyl complexes[Ta{η⁵-C₅H₃(SiMe₃)₂}Cl_4−xMe_x] (x = 2, 11; 3, 12), while the use of 4 equivalents of MgClMe converts 1c into the tetramethyl derivative [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Me₄] (13). Finally, a tetramethyl tantalum complex [Ta{η⁵-C₅H₃(SiMe₃)₂}Me₄] (14) was prepared by reaction of [Ta{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1c; Me, 1d) with 5 (X = Cl) or 4 (X = Me) equivalents of MgClMe in diethyl ether (X = Cl) or hexane (X = Me), respectively, as solvent. All the complexes were studied by IR and NMR spectroscopy and the molecular structure of the complex 11 was determined by X-ray diffraction methods.     

Cationic half-sandwich complexes (Rh, Ir, Ru) containing 2-substituted-1,8-naphthyridine chelating ligands: Syntheses, X-ray structure analyses and spectroscopic studies

Reactions of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me) and [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) with 2-substituted-1,8-naphthyridine ligands, 2-(2-pyridyl)-1,8-naphthyridine (pyNp), 2-(2-thiazolyl)-1,8-naphthyridine (tzNp) and 2-(2-furyl)-1,8-naphthyridine (fuNp), lead to the formation of the mononuclear cationic complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ {L = pyNp (1); tzNp (2); fuNp (3)}, [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ {L = pyNp (4); tzNp (5); fuNp (6)}, [(η⁵-C₅Me₅)Rh(L)Cl]⁺ {L = pyNp (7); tzNp (8); fuNp (9)} and [(η⁵-C₅Me₅)Ir(L)Cl]⁺ {L = pyNp (10); tzNp (11); fuNp (12)}. All these complexes are isolated as chloro or hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV/Vis spectroscopy. The molecular structures of [1]Cl, [2]PF₆, [4]PF₆, [5]PF₆ and [10]PF₆ have been established by single crystal X-ray structure analysis.     

Titanium(IV) carboxylate complexes: Synthesis,structural characterization and cytotoxic activity

Four titanium(IV) carboxylate complexes [Ti(η⁵-C₅H₅)₂(O₂CCH₂SMes)₂] (1), [Ti(η⁵-C₅H₄Me)₂(O₂CCH₂SMes)₂] (2), [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)(O₂CCH₂SMes)₂] (3) and [Ti(η⁵-C₅Me₅)(O₂CCH₂SMes)₃] (4; Mes = 2,4,6-Me₃C₆H₂) have been synthesised by the reaction of the corresponding titanium derivatives [Ti(η⁵-C₅H₅)₂Cl₂], [Ti(η⁵-C₅H₄Me)₂Cl₂], [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)Cl₂] and [Ti(η⁵-C₅Me₅)Cl₃] and two (for 1–3) or three (for 4) equivalents of mesitylthioacetic acid. Complexes 1–4 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2 and 4 have been determined by X-ray diffraction studies. The cytotoxic activity of 1–4 was tested against tumor cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, that is peripheral blood mononuclear cells PBMC and compared with those of the reference complexes [Ti(η⁵-C₅H₅)₂Cl₂] (R1), [Ti(η⁵-C₅H₄Me)₂Cl₂] (R2), [Ti(η⁵-C₅H₅)(η⁵-C₅H₄SiMe₃)Cl₂] (R3) and cisplatin. In all cases, the cytotoxic activity of the carboxylate derivatives was higher than that of their corresponding dichloride analogues, indicating a positive effect of the carboxylato ligand on the final anticancer activity. Complexes 1–4 are more active against K562 (IC₅₀ values from 72.2 to 87.9 μM) than against HeLa (IC₅₀ values from 107.2 to 142.2 μM) and Fem-x cells (IC₅₀ values from 90.2 to 191.4 μM).     

Insertion of alkynes into the heterocycle of (η-pentaalkyl-2,3-dihydro-1,3-diborolyl)(η-pentamethylcyclopentadienyl)ruthenium: Formation and characterization of 4-borataborepine ruthenium complexes

The violet ruthenium complex [(η⁵-C₅Me₅)Ru(η⁵-C₃B₂Me₄R¹)] (2a, R¹ = Me) reacts with terminal alkynes R²CCH to give yellow 4-borataborepine compounds [(η⁵-C₅Me₅)Ru{η⁷-(MeC)₃(R¹B)₂(R²C₂H)}] (4c, R¹ = Me, R² = Ph; 4d, R¹ = Me, R² = SiMe₃; 4e, R¹ = Me, R² = H). The insertion of alkynes into the folded C₃B₂ heterocycle of 2a causes some steric hindrance, which yields with elimination of the distant boranediyl group the corresponding boratabenzene complexes 5 as byproducts. The analogous reactions with internal alkynes R²CCR² proceed slowly and afford predominantly the boratabenzene complexes [(η⁵-C₅Me₅)Ru{η⁶-(MeC)₃(MeB)(R²C)₂}] (5f, R² = Et, 5g, R² = p-tolyl), respectively. In the latter case, three byproducts are formed: methylboronic acid and 1,2,3,4-tetra-p-tolyl-1,3-butadiene (9) due to hydrolysis of the postulated 2,3,4,5-tetra-p-tolyl-1-methylborole (10) and unexpectedly, the cationic triple-decker complex [{(η⁵-C₅Me₅)Ru}₂{μ,η⁷-(MeC)₃(MeB)₂(CH)₂}]Cl (11) having two separated CH groups. The new compounds were characterized by NMR, MS, and single-crystal X-ray studies of 4c, 5f, 9 and 11.     

Trimethylstannyl (diphenylphosphino)acetate: a source of (diphenylphosphino)acetate ligand in the synthesis of coordination compounds

Trimethylstannyl (diphenylphosphino)acetate (1), which is readily accessible from potassium (diphenylphosphino)acetate and trimethylstannyl chloride, may serve as the source of (diphenylphosphino)acetate anion in the preparation of coordination compounds. Thus, the reactions between [M(cod)Cl₂] (M = Pd and Pt; cod = η²:η²-cycloocta-1,5-diene) and two equivalents of 1 give [M(Ph₂PCH₂CO₂-κ²O,P)₂] (2 and 3), while the reaction of [{Pd(μ-Cl)Cl(PFur₃)}₂] (4; Fur = 2-furyl) with one equivalent of 1 yields [SP-4-3]-[PdCl(Ph₂PCH₂CO₂-κ²O,P)(PFur₃)] (5). The reactions of 1 with the dimers [{Rh(η⁵-C₅Me₅)Cl(μ-Cl)}₂] and [{Ru(η⁶-1,4-MeC₆H₄(CHMe₂))Cl(μ-Cl)}₂] (at 1-to-metal ratio 1:1) produce O,P-chelated complexes as well, albeit as stable adducts with the liberated Me₃SnCl: [RhCl(η⁵-C₅Me₅)(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (6) and[RuCl(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂-κ²O,P)] · Me₃SnCl (8). The related complexes with P-monodentate (diphenylphosphino)acetic acid, [RhCl₂(η⁵-C₅Me₅)(Ph₂PCH₂CO₂H-κ,P)] (7) and [RuCl₂(η⁶-1,4-MeC₆H₄(CHMe₂))(Ph₂PCH₂CO₂H-κP)] (9), were obtained by bridge splitting in the dimers with the phosphinocarboxylic ligand. All new compounds were characterized by spectral methods and combustion analyses, and the structures of 2 · 3CH₂Cl₂, 3, 4, 5, 6 and 8 were determined by X-ray crystallography.     

Complexes of titanium and zirconium based on [C5Me4CH2-(2-C5H4N)] ligand

Half-sandwich [η⁵:η¹-κN-C₅Me₄CH₂-(2-C₅H₄N)]MCl₃ (M = Ti (4), Zr (5)) and sandwich [η⁵-C₅Me₄CH₂-(2-C₅H₄N)][η⁵-C₅Me₅]ZrCl₂ (6) ring-peralkylated complexes have been prepared and characterized. Evidence of the intramolecular coordination of the side-chain pyridyl group both in 4 and 5 in solutions is provided by NMR spectroscopy data. Crystal structure of an adduct 5-py with one molecule of pyridine has been established by X-ray diffraction analysis.     

Titanocene - 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl complexes - crystal structures and their retro reaction

Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magnesium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(η⁵-C₅H_5 − nMe_n)₂ (n = 5 (1), 4 (2), and 3 (3)) and Ti{Me₂Si(η⁵-C₅Me₄)₂} (4). The non-methylated titanocene moiety affords under identical conditions known diamagnetic bis(η⁵-cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl)titanacyclopenta-2,4-diene (5) as the major product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl ligand as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90 °C, however, it undergoes retroreaction when oxidized by PbCl₂ in THF, yielding nearly quantitatively BSD and [TiCl₂(η⁵-C₅Me₅)₂].     

Group VIII transition metal complexes with the chiral diphosphazane ligand (S)-α-(Ph2P)2N(CHMePh): Synthesis and structural characterization

The chiral ligand S-(Ph₂P)₂N(CHMePh) reacts with Ni(CO)₄ in benzene solution to yield the mononuclear complex [Ni(CO)₂{κ²-(PPh₂)₂N(CHMePh)}] (1). The reactions of the chiral ligand with the solvated complexes [(η⁵-C₅Me₅)MCl(solvent)₂]BF₄ (M = Rh, Ir) or with the binuclear complex [{(η⁶-C₆Me₆)RuCl}₂(μ-Cl)] in the presence of a chloride scavenger, give cationic complexes of the type [(ηⁿ-ring)MCl{κ²-(PPh₂)₂N(CHMePh)}]BF₄ [ηⁿ-ring = η⁵-C₅Me₅; M = Rh (2), Ir (3). η⁶-C₆Me₆; M = Ru (4)]. The ³¹P NMR spectra of compounds 2-4 show two signals corresponding of two phosphorus nuclei with different chemical environments. The related complex [(η⁵-C₅H₅)Fe(CO){κ²-(PPh₂)₂N(CHMePh)}]BF₄ (5) was prepared by reaction of the ligand with the complex [(η⁵-C₅H₅)Fe(CO)₂I] in toluene following by a metathesis with AgBF₄. This compound exhibits only one signal in the ³¹P NMR spectra at room temperature, which splits into two signals at low temperature (213 K). The crystal structures of complexes 2, 3 and 5 have been determined by X-ray diffraction studies. All complexes show the presence of an intramolecular π-stacking interaction. The separation between least-squares planes defined by the two intramolecularly stacked phenyl rings are in the range 3.318-3.649 Å.     

Synthesis and reactivity of homo-bimetallic Rh and Ir complexes containing a N,O-donor Schiff base

Binuclear complexes [{(η⁵-C₅Me₅)RhCl}₂(μ-bsh)] (1) and [{(η⁵-C₅Me₅)IrCl}₂(μ-bsh)] (2) containing N,N′-bis(salicylidine)hydrazine (H₂bsh) are reported. The complexes 1 and 2 reacted with EPh₃ (E = P, As) to afford cationic complexes [(η⁵-C₅Me₅)Rh(PPh₃)(κ²-Hbsh)]PF₆ (3), [(η⁵-C₅Me₅)Rh(AsPh₃)(κ²-Hbsh)]PF₆ (4), [(η⁵-C₅Me₅)Ir(PPh₃)(κ²-Hbsh)]PF₆ (5), and [(η⁵-C₅Me₅)Ir(AsPh₃)(κ²-Hbsh)]PF₆ (6) which were isolated as their hexafluorophosphate salts. Representative complexes 3 and 5 have been used as a metallo-ligand in the synthesis of binuclear complexes [(η⁵-C₅Me₅)RhCl(μ-bsh)Ru(η⁶-C₁₀H₁₄)Cl]PF₆ (7) and [(η⁵-C₅Me₅)IrCl(μ-bsh)Ru(η⁶-C₁₀H₁₄)Cl]PF₆ (8). The complexes under study have been fully characterized by analytical and spectral (FAB/ESI-MS, IR, NMR, electronic and emission) studies. Molecular structures of 1, 2, 3 and 5 have been determined crystallographically. Structural studies on 1 and 2 revealed the presence of extensive inter- and intra-molecular C-H···O and C-H···π weak bonding interactions. The complexes 1, 2, 3 and 5 moderately emit upon excitation at their respective MLCT bands.     

Formation of ferraboranes from pentaborane(9) or BH3 · thf and an electron-rich cyclopentadienyl iron phosphine hydride

[(η⁵-C₅R₅)Fe(PMe₃)₂H] (R = H, Me) can be made in good yields in a simple one-pot reaction between FeCl₂, PMe₃, C₅R₅H (R = H, Me) and Na/Hg in thf. Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with pentaborane(9) gives the known metallaborane [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (1) in improved yield as well as the new metallaboranes [(η-C₅H₅)-nido-2-FeB₅H₈{μ-5,6-Fe(η⁵-C₅H₅)(PMe₃)(μ-6,7-H)}] (2), [(η-C₅H₅)(PMe₃)-arachno-2-FeB₃H₈] (3), [(η⁵-C₅H₅)₂-capped-nido-2,3-Fe₂B₄H₈] (4), [(η⁵-C₅H₅)-nido-2-FeB₄H₇(PMe₃)] (5) and [(η⁵-C₅H₅)-nido-2-FeB₅H₈(PMe₃)] (6). Reaction of [(η⁵-C₅Me₅)Fe(PMe₃)₂H] with pentaborane(9) gives predominantly [(η⁵-C₅Me₅)-nido-2-FeB₅H₁₀] (7) and [(η⁵-C₅Me₅)(PMe₃)-arachno-2-FeB₃H₈] (8). Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with 2 equiv. of BH₃ · thf gives low yields of ferrocene and compound 3. Compound 7 thermally isomerises to the apical isomer [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (9) in low yield. Compounds 1 and 7 deprotonate cleanly in the presence of KH at the unique B-H-B bridge to give [(η⁵-C₅H₅)-nido-2-FeB₅H₉⁻][K⁺] (10) and [(η⁵-C₅Me₅)-nido-2-FeB₅H₉⁻][K⁺] (11) respectively, whilst 6 deprotonates more slowly at one of two equivalent B-H-B bridges to give the fluxional anion [(η⁵-C₅H₅)-nido-2-FeB₅H₇(PMe₃)⁻] (12).