Comparative reactivity study of cyclopentadienyl and fulvalene molybdenum complexes

The reactions of cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆ (1), in the presence of 1 equiv. of Me₃NO, and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]₂ (2) with dppe produce CO labilization and formation of the dinuclear zwitterions trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₅(dppe) (3) and disproportionation species [(η⁵-C₅H₄CO₂Me)Mo(CO)₂(dppe)]⁺ [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ (4), respectively. Using the same method, the reactions of trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆I₂ and (η⁵-C₅H₄CO₂Me)Mo(CO)₃I with PPh₃ in the presence of 1 and 2 equiv. of Me₃NO yield trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(PPh₃)₂I₂ (5) and (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)I (6). The reactions of the several anionic carbonyl species {trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆}²⁻, [(η⁵:η⁵-C₁₀H₈)W₂(CO)₆]²⁻ and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ with S₂Ph₂ give rise to the thiolate–fulvalene complexes cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(μ-SPh)₂ (7) and (η⁵:η⁵-C₁₀H₈)W₂(CO)₆(SPh)₂ (8) and the thiolate-bridged dimer [(η⁵-C₅H₄CO₂Me)Mo(CO)(μ-SPh)]₂ (9). Treatment of 6 with 1 equiv. of HCCCCH and with (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH), in the presence of CuI at room temperature, afford the cyclopentadiene complexes (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)(CCCCH) (10) and (η⁵-C₅H₄CO₂Me)(PPh₃)(CO)₂Mo(CCCC)Mo(CO)(dppe)(η⁵-C₅H₅) (11), respectively. The reaction of (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH) with Co₂(CO)₈ yields [Co₂{μ-HC₂CC[Mo(CO)(dppe)(η⁵-C₅H₅)]}(CO)₆] (12). All the new compounds have been characterized by analytical and spectroscopic methods.     

Coordination chemistry of molybdenum relevant to hydrodenitrogenation: Reactivity of Mo(PMe3)6 towards 6-membered heterocyclic aromatic nitrogen compounds involving C-H bond cleavage and η-coordination

The reactivity of Mo(PMe₃)₆ towards 6-membered heterocyclic aromatic nitrogen compounds, namely pyridine, pyrazine, pyrimidine and triazine, has been investigated as part of an effort to define the coordination chemistry of molybdenum relevant to hydrodenitrogenation. For example, Mo(PMe₃)₆ reacts with pyridine to yield initially (η²-N,C-pyridyl)Mo(PMe₃)₄H, an uncommon example of an η²-pyridyl-hydride complex. The formation of (η²-N,C-pyridyl)Mo(PMe₃)₄H is reversible and treatment with PMe₃ regenerates Mo(PMe₃)₆ and pyridine. At elevated temperatures, (η²-N,C-pyridyl)Mo(PMe₃)₄H dissociates PMe₃ and converts to the η⁶-pyridine complex (η⁶-pyridine)Mo(PMe₃)₃. Pyrazine, pyrimidine and 1,3,5-triazine likewise react with Mo(PMe₃)₆ to yield (η²-N,C-pyrazinyl)Mo(PMe₃)₄H, (η²-N,C-pyrimidinyl)Mo(PMe₃)₄H and (η²-N,C-triazinyl)Mo(PMe₃)₄H, respectively. At elevated temperatures (η²-N,C-pyrazinyl)Mo(PMe₃)₄H and (η²-N,C-pyrimidinyl)Mo(PMe₃)₄H dissociate PMe₃ and convert to (η⁶-pyrazine)Mo(PMe₃)₃ and (η⁶-pyrimidine)Mo(PMe₃)₃ in which the heterocycle coordinates to molybdenum in an unprecedented η⁶-manner.     

Reactions of ‘GaI’ with organometallic transition metal halides

Two approaches towards the synthesis of phosphine ligated half-sandwich complexes [(η^x-C_xH_x)M(PR₃)₂GaI₂]_n containing diiodogallyl ligands have been investigated. Insertion of ‘GaI’ into the Mo-I bond of (η⁷-C₇H₇)Mo(CO)₂I has been shown to yield the crystallographically characterized dimeric complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂ (2). Attempts to substitute the carbonyl ligands by the phosphine ligand dppe [dppe = bis(diphenylphosphino)ethane] have been shown instead to yield the sparingly soluble complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂(μ-dppe) (3) in which the phosphine bridges two [(η⁷-C₇H₇)Mo(CO)₂GaI₂] units via a pair of P → Ga donor/acceptor bonds. By contrast, attempts to insert ‘GaI’ directly into the metal-halogen bond of phosphine ligated complexes such as (η⁵-C₅H₅)Ru(PPh₃)₂Cl or (η⁵-C₅H₅)Ru(dppe)Cl have been shown to result in the formation of the tetraiodogallate species(η⁵-C₅H₅)Ru(PPh₃)₂(μ-I)GaI₃ (5) and [(η⁵-C₅H₅)Ru(dppe)]⁺[GaI₄]⁻ (7).     

Preparation of planar chiral ferrocenes containing a fluorous alcohol function

Ferrocene reacts with hexafluoroacetone trihydrate in refluxing octane to afford >80% yields of [CpFe(η⁵-C₅H₄C(CF₃)₂OH)] (X-ray), carrying out the reactions at 180 °C gives an additional 5% yield of [Fe(η⁵-C₅H₄C(CF₃)₂OH)₂] (X-ray).The mono alcohol is lithiated with Bu^tOK/BuⁿLi/TMEDA affording partial conversion to mixtures of [CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(X)] and [Fe(η⁵-C₅H₄X)(1,2-η⁵-C₅H₃C(CF₃)₂OH)(X)] (X = SMe, CPh₂OH) upon reaction with Me₂S₂ or OCPh₂.For X = CPh₂OH both structures are crystallographically characterised.Enantiopure [CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(SMe)] can be prepared from (R)-[CpFe(η⁵-C₅H₄S(O)C₆H₄Me)] via [CpFe(1,2-η⁵-C₅H₃S(O)C₆H₄Me)(C(CF₃)₂OH)] (X-ray) or [CpFe(1,2-η⁵-C₅H₃S(O)C₆H₄Me)(SMe)].Related procedures allow the preparation of [CpFe(1,2-η⁵-C₅H₃CPh₂OH)(Y)] (Y = SMe, CHO (X-ray), C(CF₃)₂OH) and[CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(CHO)].     

An NMR study of some reactions of an arachno-molybdapentaborane: Formation of an unstable nido-molybdapentaborane

Photolysis of the molybdaborane [(η⁵-C₅H₅)(η⁵:η¹-C₅H₄)-arachno-2-MoB₄H₇] (1) in benzene-d₆ gives ca. 60% conversion to the compound [(η⁵-C₅H₅)(η⁵:η¹-C₅H₄)-nido-2-MoB₄H₅] (2). Compound 2 could not be isolated as a solid and is thermally unstable at 20 °C in solution with a half-life of 3-4 h. Repeated photolysis and thermolysis of 1 in the presence of BH₃ · thf gives a low yield of the known metallacarbaborane [(η⁵-C₅H₅)(η²:η³-C₃H₃)-closo-1-MoC₂B₉H₉] (3) suggesting that 3 is formed from 1 via 2. Reaction of 1 with PEt₃ gives initially [(η⁵-C₅H₅)(η⁵:η¹-C₅H₄)-arachno-2-MoHB₄H₄PEt₃] (4). Longer reaction times (>10 min, 20 °C) give in addition [(η⁵-C₅H₅)(η⁵:η¹-C₅H₄)-arachno-1-MoHB₃H₃PEt₃] (5). Both 4 and 5 are unstable in solution or the solid state decomposing to the molybdacarbaborane [(η⁵-C₅H₅)(η³:η²- C₃H₃)-nido-1-MoC₂B₃H₅] (6), [Mo(η-C₅H₅)₂H₂] and BH₃ · PEt₃. Compound 1 is deprotonated cleanly by KH in thf at the Mo-H-B bridging proton to give (7).     

Reaction of cyanamide and their derivatives with (η-C5H5)Mn(CO)3 and (η-C5H4CH3)Mn(CO)3

The reaction of cyanamide and its derivatives with the (η⁵-C₅H₅)Mn(CO)₂(THF) and (η⁵-C₅H₄CH₃)Mn(CO)₂(THF) complexes affords the cyanamide substituted complexes of types (η⁵-C₅H₅)Mn(CO)₂(NCN(R′)(R″)) (2a-d) and (η⁵-C₅H₄CH₃)Mn(CO)₂(NCN(R′)(R″)) (3a-e). All complexes were characterized by spectroscopy (¹H, ¹³C NMR, IR), elemental and mass spectroscopy analysis. Complex 2b (η⁵-C₅H₅)Mn(CO)₂(NCN(CH₃)₂) was additionally examined by single crystal X-ray structure determination.     

C-ansa-zirconocene complexes with O/S donor ligands: Novel homoleptic six coordinate 4-mercaptophenolate complex of Zr(IV)

New C-ansa-zirconocene complexes containing methoxythiophenolate and mercaptophenolate ligands have been synthesized and characterized. The reaction of (HSC₆H₄-n-OMe) (n = 2, 3 or 4) with [Zr{(t-Bu)HC(η⁵-C₅Me₄)(η⁵-C₅H₄)}Me₂] (1) led to the formation of monosubstituted complexes [Zr{(t-Bu)HC(η⁵-C₅Me₄)(η⁵-C₅H₄)}Me(κ,S-SC₆H₄-n-OMe)] (n = 2 (2); n = 3 (3)) and the disubstituted complex [Zr{(t-Bu)HC(η⁵-C₅Me₄)(η⁵-C₅H₄)}(κ,S-SC₆H₄-4-OMe)₂] (4). The complexes [Zr{(R)HC(η⁵-C₅Me₄)(η⁵-C₅H₄)}(κ,O-OC₆H₄-4-SH)₂] (R = t-Bu (6); R = CH₂CHCH₂ (7)) and [Zr(η⁵-C₅H₄)₂(OC₆H₄-n-SH)₂] (n = 3 (9); n = 4 (10)) have been synthesized using the corresponding dimethyl zirconocene and mercaptophenol. However, the reaction of [Zr{(t-Bu)HC(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (11) with 4-mercaptophenol in the presence of NEt₃ led to the formation of the first example of a homoleptic six-coordinate mercaptophenolate complex of zirconium, namely [HNEt₃]₂[Zr(κ,O-OC₆H₄-4-SH)₆] (12). Complex 12 can be obtained in higher yield by the reaction of ZrCl₄ with six equivalents of 4-mercaptophenol and NEt_3. The reaction of 12 with [Zr(η⁵-C₅H₄)₂Cl₂] gave the unexpected disubstituted complex [Zr(η⁵-C₅H₄)₂(OC₆H₄-4-SH)₂] (10). The molecular structures of 4 and 12 have been determined by single-crystal X-ray diffraction studies.     

Synthesis and non-linear optical properties of (η-pentaphenylcyclopentadienyl)dicarbonylruthenium(II) σ-alkenyl complexes

The complexes [Ru{(Z)-HCCHPh}(CO)₂(η⁵-C₅Ph₅)] (1) and [Ru{(Z)-HCCHC₆H₄NO₂}(CO)₂(η⁵-C₅Ph₅)] (2) have been synthesized and their identity confirmed by single-crystal X-ray diffraction studies. Reaction of 2 with PMe₂Ph and Me₃NO in tetrahydrofuran afforded [Ru{(Z)-HCCHC₆H₄NO₂}(CO)(PMe₂Ph)(η⁵-C₅Ph₅)] (3). Cyclic voltammetry confirms the expected increase in ease of oxidation on proceeding from 2 to 1 and from 2 to 3. Hyper-Rayleigh scattering studies at 1064 nm reveal a dramatic increase in quadratic non-linearity on co-ligand replacement of CO by PMe₂Ph, in proceeding from 2 to 3. Z-scan studies at 800 nm are consistent with significant contribution from two-photon states, and with an increase in γ_real on co-ligand replacement of CO by PMe₂Ph in proceeding from 2 to 3.     

The reaction of [η:C5H4-(CH2)n-C6H5]2MCl2 complexes (n=1-5; M=Zr, Hf) with EtLi

The reaction of metallocene complexes of the type [η⁵:C₅H₄-(CH₂)_n-C₆H₅]₂MCl₂ (n=1-5; M=Zr, Hf) with EtLi gives the mono nuclear ethyl derivatives [η⁵:C₅H₄-(CH₂)_n-C₆H₅]₂M(Et)Cl and the metallacycles [η⁵:C₅H₄-(CH₂)_n-C₆H₅][η⁵:C₅H₄-(CH₂)_n-η¹:C₆H₄]MEt. A large excess of EtLi affords the dinuclear species [η⁵:C₅H₄-(CH₂)_n-η⁶:C₆H₅]₂M₂Cl₂ (n=2-5). All types of complexes can be activated with methylalumoxane (MAO) and then be used for catalytic polymerization of ethylene.     

Synthesis, spectroscopic and electrochemical characterization of water soluble [(η-C5H5)2Mo(thionucleobase/thionucleoside)]Cl2 complexes

A series of water soluble molybdenocene complexes of general formula [(η⁵-C₅H₅)₂Mo(L)]Cl₂ (L=6-mercaptopurine (2), 6-mercaptopurine ribose (3), 2-amino-6-mercaptopurine (4), 2-amino-6-mercaptopurine ribose (5)) have been prepared by reacting Cp₂MoCl₂ (1) with the corresponding thionucleobase/thionucleoside in a (2:1) THF/MeOH solvent mixture. The complexes have been characterized by spectroscopic methods (NMR, UV-Vis, IR and MS). ¹H NMR spectroscopic data (DMSO-d₆) on the complexes suggest a S-Mo-N(7) coordination by the thionucleobase/thionucleoside. In buffer solution NMR data suggest that the thionucleobase/thionucleoside remains coordinated to molybdenum probably through S(6) and assisted by either N(7) or N(1) atoms. Intermediate species such as [Cp₂Mo(η¹-L)(H₂O)]^2+/1+ where the L is acting as monodentate ligand are possible in solution. Electrochemical characterization has also been pursued by cyclic voltammetry in DMSO and buffer solution. In DMSO, the complexes including the molybdenocene dichloride exhibit reversible redox behavior. On the other hand, in buffer solution, the oxidation process is irreversible for all the species.     

Intramolecular activation of pendant alkenyl group as a tool for modification of the zirconocene framework

The diphenyl zirconocene [(η⁵-C₅H₅){η⁵-C₅H₄CMe₂(CH₂)₂CHCH₂}ZrPh₂] (2) was readily obtained from the corresponding zirconocene dichloride 1 and two equivalents of phenyllithium. Upon thermal treatment at 80 °C, complex 2 released benzene, with concomitant activation of the pendant double bond and formation of intramolecularly α-tethered zirconaindane [(η⁵-C₅H₅){η⁵,η¹,η¹-C₅H₄CMe₂(CH₂)₂CHCH₂C₆H₄}Zr] (3). Both Zr-C σ-bonds in 3 easily undergo nucleophilic reactions with two equivalents of HCl or one equivalent of Cl₂PPh giving rise to zirconocene dichlorides with pendant phenyl group [(η⁵-C₅H₅){η⁵-C₅H₄CMe₂(CH₂)₄Ph}ZrCl₂] (4) or with 1-phenylphosphindolinyl moiety [(η⁵-C₅H₅){η⁵-C₅H₄CMe₂(CH₂)₂cyclo-CHCH₂C₆H₄P(Ph)}ZrCl₂] (5), respectively.     

Optically active iridium complexes with cyclopentadienyl-phosphine ligands: synthesis and oxidative addition of methyl iodide

The dimer [Ir(μ-Cl)(C₈H₁₄)₂]₂ reacts with the ligands (S)-(C₅H₄CH₂CH(Ph)PPh₂)Li and (R)-(C₅H₄CH(Cy)CH₂PPh₂)Li to give (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(C₈H₁₄)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(C₈H₁₄)], which upon treatment with CH₃I at room temperature afford the cationic iridium(III) compounds (S,S_Ir)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(C₈H₁₄)][I] as a single diastereomer, and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(C₈H₁₄)][I] as a 9:1 mixture of two diastereomers. If the oxidative addition reaction is performed at reflux in methylene chloride, the starting complexes convert to the neutral compounds (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(I)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(I)] as 1.6:1 and 3.3:1 mixtures of diastereoisomers, respectively. Carbonyl iridium complexes are synthesized by reacting [IrCl(CO)(PPh₃)₂] with the ligands to afford (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CO)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CO)]. They give upon treatment with CH₃I the cationic species (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(CO)][I] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(CO)][I] as 1.6:1 and 3:1 mixture of diastereomers, respectively. No migratory-insertion of the methyl group into the carbonyl-metal bond has been observed even after prolonged heating.     

Monocyclopentadienyl titanium complexes supported by functionalized carboxylate ligands

The reaction of [TiCp*Cl₃] with [Fe(η⁵-C₅H₅)(η⁵-C₅H₄COOH)] in the presence of NEt₃ yields [TiCp*{(OOC-C₅H₄)FeCp}₃] (1), (Cp = η⁵-C₅H₅). The alkyl complex [TiCp*Me₃] reacts with [FeCp(η⁵-C₅H₄-CH₂COOH)] or anthranilic acid rendering the tris-carboxylate titanium complexes [TiCp*{(OOCCH₂-C₅H₄)FeCp}₃] (2) and [TiCp*{(OOCC₆H₄NH₂)₃] (3), respectively. Complex 3 can be protonated with triflic acid to render [TiCp*{(OOCC₆H₄NH₂)₃].HOTf (4). The reaction of [TiCp*Me₃] with anthranilic acid in a 1:2 M ratio yields the alkyl carboxylate derivative [TiCp*Me{(OOCC₆H₄NH₂)₂] (5). Complex 5 reacts with ^tBuNC to render the iminoacyl complex [TiCp*(η²-MeCN^tBu){(OOCC₆H₄NH₂)₂] (6). The reaction of [TiCp*Cl₃] with the ferroceneacetic acid, gives [TiCp*Cl₂{(OOCCH₂-C₅H₄)FeCp}] (7). The [TiCp*Cl]₂(μ-O)[(ΟΟC-C₅H₄)₂Fe] (8) can be obtained by reaction of [TiCp*Cl₃] with [Fe(η⁵-C₅H₄-COOH)₂] in the presence of a base. The molecular structures of 1 and 8 have been established by X-ray diffraction methods.     

Adduct formation of [(η-C7H7)Zr(η-C5H5)] with phosphines and N-heterocyclic carbenes: An experimental and theoretical study

The reaction of [(η⁷-C₇H₇)Zr(η⁵-C₅H₅)] with two Lewis bases, tetramethylimidazolin-2-ylidene and PMe₃, is reported and their stability probed via spectroscopic and theoretical methods. The strongly σ-basic N-heterocyclic carbene forms a stable adduct which has been structurally characterised, whilst the PMe₃ ligand coordinates weakly to the metal centre. Variable temperature ³¹P NMR spectroscopy has been used to determine the activation energy for this process (ΔG^‡ = 40.5 ± 1.9 kJ mol⁻¹). DFT calculations have been performed on both complexes and the structures discussed. In addition, the enthalpies for the formation of these compounds have been calculated [ΔH⁰(Zr-IMe) = −56.3 kJ mol⁻¹; ΔH⁰(Zr-PMe₃) = −2.3 kJ mol⁻¹] and show that the N-heterocyclic carbene forms a thermodynamically much more stable adduct than that with PMe₃.     

Synthesis and properties of new trinuclear Mo(II) complexes containing imidazole and benzimidazole ferrocene units

The reaction of FcCOCl (Fc = (C₅H₅)Fe(C₅H₄)) with benzimidazole or imidazole in 1:1 ratio gives the ferrocenyl derivatives FcCO(benzim) (L1) or FcCO(im) (L2), respectively. Two molecules of L1 or L2 can replace two nitrile ligands in [Mo(η³-C₃H₅)(CO)₂(CH₃CN)₂Br] or [Mo(η³- C₅H₅O)(CO)₂(CH₃CN)₂Br] leading to the new trinuclear complexes [Mo(η³-C₃H₅)(CO)₂(L)₂Br] (C1 for L = L1; C3 for L = L2) and [Mo(η³-C₅H₅O)(CO)₂(L)₂Br] (C2 for L = L1; C4 for L = L2) with L1 and L2 acting as N-monodentade ligands. L1, L2 and C2 were characterized by X-ray diffraction studies. [Mo(η³-C₅H₅O)(CO)₂(L1)₂Br] was shown to be a trinuclear species, with the two L1 molecules occupying one equatorial and one axial position in the coordination sphere of Mo(II). Cyclic voltammetric studies were performed for the two ligands L1 and L2, as well as for their molybdenum complexes, and kinetic and thermodynamic data for the corresponding redox processes obtained. In agreement with the nature of the frontier orbitals obtained from DFT calculations, L1 and L2 exhibit one oxidation process at the Fe(II) center, while C1, C3, and C4 display another oxidation wave at lower potentials, associated with the oxidation of Mo(II).     

Reactions of the borole complex CpRh(η-C4H4BPh) with monocationic organometallic fragments

The B-phenylborole complex CpRh(η⁵-C₄H₄BPh) (1) reacts with [ML]⁺ fragments to give the arene-type cationic complexes [CpRh(μ-η⁵:η⁶-C₄H₄BPh)ML]⁺ (ML = RuCp^∗ (3), Co(C₄Me₄) (4), Rh(cod) (5), and Ir(cod) (6)). Cation 4 undergoes a reversible rearrangement into the triple-decker complex [CpRh(μ-η⁵:η⁵-C₄H₄BPh)Co(C₄Me₄)]⁺ (7) under visible light irradiation in CH₂Cl₂ solution. DFT calculations revealed greater stability of arene-type complexes over triple-decker isomers. The structure of [3]BF₄ was determined by X-ray diffraction.     

Synthesis of cyclopentadienyl ruthenium(II) complexes containing tethered functionalities

The reaction of [C₅H₄(CH₂)_nX]Tl (1: n = 2, X = NMe₂, OMe, CN; n = 3, X = NMe₂) with [(η⁶-C₆H₆)RuCl(μ-Cl)]₂, 2, afforded the sandwich compounds [{η⁵-C₅H₄(CH₂)_nX}Ru(η⁶-C₆H₆)]PF₆, 3, and [η⁵-C₅H₄(CH₂)_nX]₂Ru, 4. Photolytic cleavage of 3 in acetonitrile afforded the tethered products [{η⁵:κN-C₅H₄(CH₂)_nX}Ru(CH₃CN)₂]PF₆, 5.     

Synthesis of benzene ruthenium triazolato complexes by [3+2] cycloaddition reactions of activated alkynes and fumaronitrile to benzene ruthenium azido complexes

The dinuclear complex [(η⁶-C₆H₆)Ru(μ-N₃)Cl]₂ (1) is obtained by the reaction of [(η⁶-C₆H₆)RuCl₂]₂ with sodium azide in ethanol. The benzene ruthenium β-diketonato complexes of the general formula [(η⁶-C₆H₆)Ru(L∩L)Cl] {L∩L = O,O′-acac (2); O,O′-bzac (3); O,O′-dbzm (4)} are obtained in methanol by the reaction of [(η⁶-C₆H₆)RuCl₂]₂ with the corresponding β-diketonates. These complexes further react with sodium azide in ethanol to yield complexes of the type [(η⁶-C₆H₆)Ru(L∩L)N₃] [L∩L = O,O′-acac (5); L∩L = O,O′-bzac (6); L∩L = O,O′-dbzm (7)]. The complexes 5-7 are obtained as well by treating 1 with sodium salts of β-diketonates. These neutral benzene ruthenium azido complexes undergo [3+2] dipolar cycloaddition reaction with activated alkynes (MeO₂CCCCO₂Me, EtO₂CCCCO₂Et) or fumaronitrile (NCHCCHCN) to yield the corresponding benzene ruthenium triazolato complexes; [(η⁶-C₆H₆)Ru(O,O′-acac){N₃C₂(CO₂Me)₂}] (8), [(η⁶-C₆H₆)Ru(O,O′-acac){N₃C₂(CO₂Et)₂}] (9), [(η⁶-C₆H₆)Ru(O,O′-acac){N₃C₂HCN}] (10), [(η⁶-C₆H₆)Ru(O,O′-bzac){N₃C₂HCN}] (11) and [(η⁶-C₆H₆)Ru(O,O′-dbzm){N₃C₂HCN}] (12). These complexes are fully characterized on the basis of microanalyses, FT-IR and FT-NMR spectroscopy. The molecular structure of [(η⁶-C₆H₆)Ru(O,O′- acac){N₃C₂(CO₂C₂H₅)₂}] (9) is confirmed by single crystal X-ray diffraction study.     

Tungsten complexes of aromatic and aliphatic thioaldehydes

Reaction of PPN[W(CO)₃(R₂PC₂H₄PR₂)(SH)] (PPN=Ph₃PNPPh₃; R=Me, 1; R=Ph, 2) with aromatic aldehydes in the presence of trifluoroacetic acid gave tungsten complexes of thiobenzaldehydes mer-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)] (R=Me, 3a-3f; R=Ph, 4a-4e) in high yields. Analogous complexes of aliphatic thioaldehydes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-SCHR^′)] (3g-3l) could only be obtained from the highly electron-rich thiolate complex 1. The structure of 3i (R^′=i-Bu) was determined by X-ray crystallography. In solution the complexes 3 and 4 are in equilibrium with small quantities of their isomers fac-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)]. Reaction of complexes 3 with dimethylsulfate followed by salt metathesis with NH₄PF₆ gave the alkylation products mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCHR^′)]PF₆ (5a-5l) as mixtures of E and Z isomers. The methylated thioformaldehyde complex mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCH₂)]PF₆ (5m) was prepared similarly. Nucleophilic addition of hydride (from LiAlH₄) to 5 initially gave thioether complexes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (mer-6) which rapidly isomerized to fac-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (fac-6).     

Study of the cytotoxicity and particle action in human cancer cells of titanocene-functionalized materials with potential application against tumors

Titanocene dichloride [Ti(η⁵-C₅H₅)₂Cl₂] (1), has been grafted onto dehydrated hydroxyapatite (HAP), Al₂O₃ and two mesoporous silicas MSU-2 (Michigan State University Silica type 2) and HMS (Hexagonal Mesoporous Silica), to give the novel materials HAP/[Ti(η⁵-C₅H₅)₂Cl₂] (S1) (1.01 wt.% Ti), Al₂O₃/[Ti(η⁵-C₅H₅)₂Cl₂] (S2) (2.36 wt.% Ti), HMS/[Ti(η⁵-C₅H₅)₂Cl₂] (S3) (0.75 wt.% Ti) and MSU-2/[Ti(η⁵-C₅H₅)₂Cl₂] (S4) (0.74 wt.% Ti), which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear magic angle spinning NMR spectroscopy, IR spectroscopy, thermogravimetry analysis, UV spectroscopy, scanning electronic microscopy and transmission electronic microscopy. The cytotoxicity of the titanocene-functionalized materials toward human cancer cell lines from five different histogenic origins: 8505 C (anaplastic thyroid cancer), A253 (head and neck cancer), A549 (lung carcinoma), A2780 (ovarian cancer) and DLD-1 (colon cancer) has been determined. M₅₀ values (quantity of material needed to inhibit normal cell growth by 50%) and Ti-M₅₀ values (quantity of anchored titanium needed to inhibit normal cell growth by 50%) indicate that the activity of S1-S4 against studied human cancer cells depended on the surface type as well as on the cell line. In addition, studies on the titanocene release and the interaction of the materials S1-S4 with DNA show that the cytotoxic activity may be due to particle action, because no release of titanium complexes has been observed in physiological conditions, while electrostatic interactions of titanocene-functionalized particles with DNA have been observed.