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).     

Synthesis and characterisation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes [Ti(IV), Zr(IV), Hf(IV), La(III), Ce(III), Yb(III), Sn(II) and Fe(II)]

The preparation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes is described. These are of formula [M{η⁵-C₅H₄(BX)}Cl₃] [M = Ti and X = CAT (2a), CAT^t (2b) or CAT^tt (2c); X = CAT^tt and M = Zr (4a) or Hf (4b)], [M{η⁵-C₅H₄(BX)}₂Cl₂] [M = Zr, X = CAT (3a) or CAT^t (3c); or M = Hf, X = CAT (3b) or CAT^t (3d)], [M{(μ-η⁵-C₅H₃BCAT)₂ SiMe₂}Cl₂] [M = Zr (5a) or Hf (5b)], [M{η⁵-C₅H₃(BCAT)₂}Cl₃] [M = Zr (6a) or Hf (6b)], [M{η⁵-C₅H₄BCAT}₃(THF)] [M = La (7a), Ce (7b) or Yb (7c)], [Sn{η⁵-C₅ H₄(BCAT^t)}Cl](8) and [Fe{η⁵-C₅H₄(BCAT^t)}₂] (9). The abbreviations refer to BO₂C₆H₄-1,2 (BCAT) and the 4-Bu^t (BCAT^t) and the (BCAT^tt) analogues. The compounds 2a-9 have been characterised by microanalysis, multinuclear NMR and mass spectra. The single crystal X-ray structure of the lanthanum compound 7a is presented.     

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, characterization and applications in ethylene polymerization of asymmetric ansa-titanocene complexes. Molecular structure of [Ti{Me2Si(η-C5Me4)(η-C5H3iPr)}Cl2]

The ansa-titanocene complexes, [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃R)}Cl₂] (R = Me (5), iPr (6), tBu (7), SiMe₃ (8)), were obtained from the reaction of Li₂{Me₂Si(C₅Me₄)(C₅H₃R)} (R = Me (1), iPr (2), tBu (3), SiMe₃ (4)) with [TiCl₄(THF)₂], respectively. Compounds 5-8 have been tested as catalysts in the polymerization of ethylene and compared with the ansa-titanocene complexes [Ti{Me₂Si(η⁵-C₅H₄)₂}Cl₂] and [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂]. The resulting polyethylene showed molecular weights of about 200 000 g mol⁻¹ and polydispersity values of approximately 3. In addition, the molecular structure of 6 has been determined by single crystal X-ray diffraction studies.     

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.     

Reactions of the pentamethylcyclopentadienyl trisulfido tungsten with M′Cl2 (M′ = Zn, Cd, Hg): Isolation and structural characterization of [PPh4][(η-C5Me5)WS3(ZnCl2)] and [{(η-C5Me5)WS3}2Hg]

Reactions of [PPh₄][(η⁵-C₅Me₅)WS₃] with equimolar M′Cl₂ (M′ = Zn, Cd) in MeCN or 0.5 equiv. of HgCl₂ in DMF afforded two binuclear clusters [PPh₄][(η⁵-C₅Me₅)WS₃(M′Cl₂)] (1: M′ = Zn; 2: M′ = Cd) and one trinuclear cluster [{(η⁵-C₅Me₅)WS₃}₂Hg] (3). Compounds 1-3 were characterized by elemental analysis, IR, UV-Vis, ¹H NMR and X-ray crystallography. Compound 1 may be viewed as a 1:1 composite of [PPh₄][(η⁵-C₅Me₅)WS₃] and ZnCl₂, in which one [(η⁵-C₅Me₅)WS₃]⁻ anion binds a ZnCl₂ moiety via two μ-S atoms. In the structure of 3, two [(η⁵-C₅Me₅)WS₃]⁻ anions coordinate the central Hg atom via two μ-S atoms, forming an unique bent linear structure. In addition, internal redox reactions of [PPh₄][(η⁵-C₅Me₅)WS₃] under the presence of M′Cl₂ (M′ = Zn, Cd, Hg) in high concentrations were discussed.     

Synthesis, molecular structure, substitution and C-C coupling reactions of ruthenium complexes containing (η-C9H7)Ru(PPh3) as a molecular unit

The 2-methallyl complex [(η⁵-C₉H₇)Ru(η³-2-MeC₃H₄)(PPh₃)] (3), prepared from [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] (2) and 2-MeC₃H₄MgCl, reacts with HX (X = Cl, CF₃CO₂) in the presence of ethene to give the chiral-at-metal compounds [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)X] (4, 5) in nearly quantitative yields. Treatment of 2 with AgPF₆ and ethene affords [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)₂]PF₆ (6), which reacts with acetone to give the substitution product [(η⁵-C₉H₇)Ru(OCMe₂)(PPh₃)₂]PF₆ (7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO₂Et)N₂ yields the olefin complex [(η⁵-C₉H₇)Ru{η²-(Z)-C₂H₂(CO₂Et)₂}(PPh₃)Cl] (8), the reactions of 4 and 5 with Ph₂CN₂, PhCHN₂ and (Me₃Si)CHN₂ lead to the formation of the carbeneruthenium(II) derivatives [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)Cl] (9-11) and [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)(κ¹-O₂CCF₃)] (12-14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe₃) with MeLi produces the hydrido(olefin) complexes [(η⁵-C₉H₇)RuH(η²-CH₂CPh₂)(PPh₃)] (15), [(η⁵-C₉H₇)RuH(η²-CH₂CHPh)(PPh₃)] (18a,b) and [(η⁵-C₉H₇)RuH(η²-CH₂CHSiMe₃)(PPh₃)] (19) via C-C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η³-benzyl compound [(η⁵-C₉H₇)Ru{η³-(Me₃Si)CHC₆H₅}(PPh₃)] (20). The η³-allyl complex [(η⁵-C₉H₇)Ru(η³-1-PhC₃H₄)(PPh₃)] (17) was prepared from 10 and CH₂CHMgBr by nucleophilic attack.     

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.     

Synthesis, characterization and cytotoxic effect of ring-substituted and ansa-bridged vanadocene complexes

The cytotoxic effect of vanadocene dichloride (Cp₂VCl₂, 1) and its ring-substituted, (η⁵-C₅H₄Me)₂VCl₂ (2), (η⁵-C₅Me₅)₂VCl₂ (3), (η⁵-C₅H₄R)₂VCl₂ (4: R = MeOCH₂CH₂-, 5: R = 2-MeOC₆H₄CH₂-, 6: R = 4-MeOC₆H₄CH₂-) and ansa-bridged analogs Me₂C(η⁵-C₅H₄)₂VCl₂ (7) and Me₄C₂(η⁵-C₅H₄)₂VCl₂ (8) was investigated. Synthesis of two new methoxy-functionalized compounds (4 and 5) is described. They were characterized by spectroscopic methods and X-ray diffraction analysis. The cytotoxicity studies were performed with leukemic cells MOLT-4.     

Cytotoxic studies of substituted titanocene and ansa-titanocene anticancer drugs

A variety of substituted titanocene and ansa-titanocene complexes have been synthesized and characterized using traditional methods. The cytotoxic activity of the different titanocene complexes was tested against tumour cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, peripheral blood mononuclear cells PBMC. Alkenyl substitution, either on the cyclopentadienyl ring or on the silicon-atom ansa-bridge of the titanocene compounds [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃{CMe₂CH₂CH₂CHCH₂})}Cl₂] (8), [Ti{Me(CH₂CH)Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (9) and [Ti(η⁵-C₅H₄{CMe₂CH₂CH₂CHCH₂})₂Cl₂] (12) showed higher cytotoxic activities (IC₅₀ values from 24 ± 3 to 151 ± 10 μM) relative to complexes bearing an additional alkenyl-substituted silyl substituent on the silicon bridge [Ti{Me{(CH₂CH)Me₂SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (10) and [Ti{Me{(CH₂CH)₃SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (11) which causes a dramatic decrease of the cytotoxicity (IC₅₀ values from 155 ± 9 to >200 μM). In addition, the synthesis of the analogous niobocene complex [Nb(η⁵-C₅H₄{CMe₂CH₂CH₂CH=CH₂})₂Cl₂] (13), is described. Structural studies based on DFT calculations of the most active complexes 8, 9 and 12 and the X-ray crystal structure of 13 are reported.     

Neighbouring metal induced oxidative addition at the iron centre amongst the iron-arylpyridylphosphine complexes

Complexes of the type (η⁴-BuC₅H₅)Fe(CO)₂(P) (P = PPh₂Py 3, PPhPy₂4, PPy₃5; Py = 2-pyridyl) were satisfactorily prepared. Upon treatment of 3 with M(CO)₃(EtCN)₃ (M = Mo, 6a; W, 6b), the pyridyl N-atom could be coordinated to the metal M, which then eliminates a CO ligand from the Fe-centre and induced an oxidative addition of the endo-C-H of (η⁴-BuC₅H₅). This results in a bridged hydrido heterodimetallic complex [(η⁵-BuC₅H₄)Fe(CO)(μ-P,N-PPh₂Py)(μ-H)M(CO)₄] (M = Mo, 7a, 81%; W, 7b, 76%). The reaction of 4 or 5 with 6a,b did not give the induced oxidative addition, although these complexes contain more than one pyridyl N-atom. The reaction of 4 with M(CO)₄(EtCN)₂ (M = Mo, 9a; W, 9b) produced heterodimetallic complexes [(η⁴-BuC₅H₅)Fe(CO)₂(μ-P:N,N′-PPhPy₂)M(CO)₄] (M = Mo, 10a, 81%; W, 10b, 83%). Treatment of 5 with 6a,b gave [(η⁴-BuC₅H₅)Fe(CO)₂(μ-P:N,N′,N″-PPy₃)M(CO)₃] (M = Mo, 12a, 96%; W, 12b, 78%).     

Bis(acetylacetonato)ruthenium(II) complexes containing bulky tertiary phosphines. Formation and redox behaviour of Ru(acac)2 (PR3) (R = Pr, Cy) complexes with ethene, carbon monoxide, and bridging dinitrogen

Reaction of cis-[Ru(acac)₂(η²-C₈H₁₄)₂] (1) (acac = acetylacetonato) with two equivalents of PⁱPr₃ in THF at −25 °C gives trans-[Ru(acac)₂(PⁱPr₃)₂], trans-3, which rapidly isomerizes to cis-3 at room temperature. The poorly soluble complex [Ru(acac)₂(PCy₃)₂] (4), which is isolated similarly from cis-[Ru(acac)₂(η²-C₂H₄)₂] (2) and PCy₃, appears to exist in the cis-configuration in solution according to NMR data, although an X-ray diffraction study of a single crystal shows the presence of trans-4. In benzene or toluene 2 reacts with PⁱPr₃ or PCy₃ to give exclusively cis-[Ru(acac)₂(η²-C₂H₄)(L)] [L = PⁱPr₃ (5), PCy₃ (6)], whereas in THF species believed to be either square pyramidal [Ru(acac)₂L], with apical L, or the corresponding THF adducts, can be detected by ³¹P NMR spectroscopy. Complexes 3-6 react with CO (1 bar) giving trans-[Ru(acac)₂(CO)(L)] [L = PⁱPr₃ (trans-8), PCy₃ (trans-9)], which are converted irreversibly into the cis-isomers in refluxing benzene. Complex 5 scavenges traces of dinitrogen from industrial grade dihydrogen giving a bridging dinitrogen complex, cis-[{Ru(acac)₂(PⁱPr₃)} ₂(μ-N₂)] (10). The structures of cis-3, trans-4, 5, 6 and 10 · C₆H₁₄ have been determined by single-crystal X-ray diffraction. Complexes trans- and cis-3, 5, 6, cis-8, and trans- and cis-9 each show fully reversible one-electron oxidation by cyclic voltammetry in CH₂Cl₂ at −50 °C with E_1/2(Ru^3+/2+) values spanning −0.14 to +0.92 V (versus Ag/AgCl), whereas for the vinylidene complexes [Ru(acac)₂ (CCHR)(PⁱPr₃)] [R = SiMe₃ (11), Ph (12)] the process is irreversible at potentials of +0.75 and +0.62 V, respectively. The trend in potentials reflects the order of expected π-acceptor ability of the ligands: PⁱPr₃, PCy₃ <C ₂H₄ < CCHR < CO. The UV-Vis spectrum of the thermally unstable, electrogenerated Ru^III-ethene cation 6⁺ has been observed at −50 °C. Cyclic voltammetry of the μ-dinitrogen complex 10 shows two, fully reversible processes in CH₂Cl₂ at −50 °C at +0.30 and +0.90 V (versus Ag/AgCl) corresponding to the formation of 10⁺ (Ru^II,III) and 10²⁺ (Ru^III,III). The former, generated electrochemically at −50 °C, shows a band in the near IR at ca. 8900 cm⁻¹ (w_1/2 ca. 3700 cm⁻¹) consistent with the presence of a valence delocalized system. The comproportionation constant for the equilibrium 10 + 10²⁺ ? 2 10⁺ at 223 K is estimated as 10^13.6.     

Water soluble (η-arene) ruthenium(II) complexes incorporating marine derived bioligand: Synthesis, spectral and structural studies

A series of water soluble compounds of general formula [{(η⁶-arene)Ru(HMP)Cl}], [η⁶-arene = η⁶-cymene (1), η⁶-HMB (2), η⁶-C₆H₆ (3); HMP = 5-hydroxy-2-(hydroxymethyl)-4-pyrone] have been prepared by the reaction of [{(η⁶-arene) RuCl₂}₂] with HMP. The complexes 1 and 2 react with NaN₃ to give in excellent yield tetra-azido complexes [{(η⁶-arene)Ru(μN₃)N₃}₂] (arene = cymene 4, HMB = 5) but similar reaction of complex 3 with NaN₃ yielded di-azdo complex [{(η⁶-C₆H₆)Ru(μN₃)Cl}₂] (6). Reaction of [{(η⁶-arene)Ru(μN₃)Cl}₂] with HMP in the presence of NaOMe resulted in the formation of azido complex [{(η⁶-arene)Ru(HMP)N₃}]. Mono and dinuclear complexes [{(η⁶-arene)Ru(HMP)(L₁)}]⁺ and [{(η⁶-arene)Ru(HMP)}₂(μL₂)]²⁺ were also prepared by the reaction of complexes 1 and 2 with the appropriate ligand, L₁ or L₂ in the presence of AgBF₄ (L₁ = PyCN, DMAP; L₂ = 4,4′-bipy, pyrazine). The complexes are characterized on the basis of spectroscopic data and molecular structures of three representative compounds have been determined by single crystal X-ray diffraction study.     

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.     

Diferrocenes containing thiadiazole connectivities

2,5-Diferrocenyl-1,3,4-thiadiazole, 2,5-Fc₂-^cC₂N₂S, (3) has been synthesized by a two-fold Negishi ferrocenylation of dibromothiadiazole (1) with FcZnCl (2) (Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅)) in presence of [Pd(Ph₃P)₄] as catalyst. Additional spacer units between the ferrocenyls and the ^cC₂N₂S core could be introduced by using the Sonogashira C,C cross-coupling protocol. Reaction of 2,5-Br₂-^cC₂N₂S (1) or 2,5-(C₆H₄-4′-I)₂-^cC₂N₂S (6) with FcCCH (4) using [PdCl₂(Ph₃P)₂] and [CuI] as catalyst produced the appropriate organometallics 2,5-(FcCC)₂-^cC₂N₂S (5) or 2,5-(C₆H₄-4′-CCFc)₂-^cC₂N₂S (7). The electronic and structural properties of 3, 5, and 7 were investigated with UV-Vis spectroscopy and single crystal X-ray diffraction (3). Complex 3 adopts a solid state structure with none of the ferrocenyl substituents being coplanar with the thiadiazole ring. Cyclic, square wave, linear sweep voltammetry and in-situ NIR spectro-electrochemistry highlight the electrochemical properties of 3. In dichloromethane (0.1 mol L⁻¹ [N(ⁿBu)₄][B(C₆F₅)₄]), compound 3 displays two well resolved electrochemical reversible one-electron events with formal reduction potentials of 0.192 and 0.338 V versus FcH/FcH⁺. In contrast, in presence of [N(ⁿBu)₄][PF₆], the thiadiazoles 3 (E⁰ = 0.22 V), 5 (E⁰ = 0.18 V) and 7 (E⁰ = 0.09 V) show simultaneously oxidation of the two ferrocenyl termini versus FcH/FcH⁺. Spectro-electrochemical studies, performed in a dichloromethane solution of 0.2 mol L⁻¹ [N(ⁿBu)₄][B(C₆F₅)₄], also show that 3 can successively be oxidized via 3⁺ to 3²⁺. A weak IVCT absorption (ε ca. 300 L mol⁻¹ cm⁻¹) at 1560 nm was found and is consistent with appreciable interactions between neutral ferrocenyl and positively charged ferrocenium mixed valent intermediates. Mixed-valent compound 3⁺ corresponds to a class II molecule according to Robin and Day.     

Ferrocenesuccinate-bridged lanthanide polymeric complexes: Syntheses, structures and properties

One-dimensional lanthanide-ferrocenesuccinate polymeric complexes [M(η²-FcCOC₂H₄COO)(μ₂-η²-FcCOC₂H₄COO)₂(H₂O)₂]_n (Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₄), M = Pr, 1; Ce, 2; La, 3) have been synthesized and structurally characterized by single-crystal X-ray crystallography. The three polymers are isomorphous, in which each Ln(III) ion is 10-coordinated and connects with two water molecules and eight oxygen atoms from ferrocenesuccinate units in two kinds of coordination modes: bidentate-chelating mode and tridentate-bridging mode. The variable-temperature magnetic susceptibility in the temperature range 5-300 K for 1 and 2 shows that both of them display weak antiferromagnetic interaction. In addition, the redox and fluorescent properties have been investigated. The redox properties are different from the previous results of transition metal compounds containing ferrocenyl systems. Compared with sodium ferrocenesuccinate, polymers 1 and 3, the fluorescent intensities of 2 are markedly enhanced in the solid state.     

Silver(I) acetylides stabilized by η-alkynes: Synthesis, reaction chemistry and solid state structures

Individual synthetic routes to heterobimetallic Ti(IV)-Ag(I) acetylides of type {[Ti](μ-σ,π-CCR¹)₂}AgCCR² ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti: R¹ = SiMe₃: 6, R² = SiMe₃; 7, R² = Ph. R¹ = ^tBu: 8, R² = SiMe₃; 9, R² = Ph. [Ti] = (η⁵-C₅H₅)₂Ti): 10, R¹ = ^tBu, R² = SiMe₃) including (i) the reaction of {[Ti](μ-σ, π-CCR¹)₂}AgNO₃ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti): 1, R¹ = SiMe₃; 2, R¹ = ^tBu. [Ti] = (η⁵-C₅H₅)₂Ti: 3, R¹ = ^tBu) with LiCCR² (4, R² = SiMe₃; 5, R² = Ph) and (ii) treatment of [Ti](CCSiMe₃)₂ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) (11) with [AgCCR²] (12, R² = SiMe₃; 13, R² = Ph) are described. The reactions of 1-3 with 4 or 5 appeared to be sensitive towards stoichiometry because an excess of 4 or 5 resulted in the formation of [(Ag(CCR²)₂)Li(OEt₂)]_n (14) and [Ti](CCR¹)₂. Coordination polymer 14 is also accessible, when, for example, [AgCCSiMe₃] (12) is treated with 1 eq. of LiCCSiMe₃ (4) in diethyl ether.The titanium(IV)-silver(I) acetylides 6-10 are stable in the dark and at low temperature, while on exposure to light and on heating they decompose to give R²CC-CCR² together with [Ti](CCR¹)₂ and elemental silver.Complexes 6-10 contain a mono-nuclear AgCCR² entity stabilized by the chelate-bonded organometallic π-tweezer molecule [Ti](CCSiMe₃)₂, which was evinced by structure determination of 7 in the solid state. In 14 linear [Me₃SiCC-Ag-CCSiMe₃]⁻ units are connected by [Li(OEt₂)]⁺ building blocks forming a coordination polymer.     

Reactivity of phenyldi(2-thienyl)phosphine towards group 7 metal carbonyls: Carbon-phosphorus bond activation

Addition of phenyldi(2-thienyl)phosphine (PPhTh₂) to [Re₂(CO)_10−n(NCMe)_n] (n = 1, 2) affords the substitution products [Re₂(CO)_10−n(PhPTh₂)_n] (1, 2) together with small amounts of fac-[ClRe(CO)₃(PPhTh₂)₂] (3) (n = 2). Reaction of [Re₂(CO)₁₀] with PPhTh₂ in refluxing xylene affords a mixture which includes 2, [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-H)] (4), [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-η¹,κ¹(S)-C₄H₃S)] (5) and mer-[HRe(CO)₃(PPhTh₂)₂] (6). Phosphido-bridged 4 and 5 are formed by the carbon-phosphorus bond cleavage of the coordinated PPhTh₂ ligand, the cleaved thienyl group being retained in the latter. Reaction of [Mn₂(CO)₁₀] with PPhTh₂ in refluxing toluene affords [Mn₂(CO)₉(PPhTh₂)] (7) and the carbon-phosphorus bond cleavage products [Mn₂(CO)₆(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (8) and [Mn₂(CO)₅(PPhTh₂)(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (9). Both 8 and 9 contain a bridging thienyl ligand which is bonded to one manganese atom in a η⁵-fashion.     

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 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.