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Cationic group 4 metallocene complexes with pendant imine and pyridine donor groups were prepared as stable crystalline [B(C6F5)4]- salts either by protonation of the intramolecularly bound ketimide moiety in neutral complexes [(η5-C5Me5){η5-C5H4CMe2CMe2C(R)═N-κN}MCl] (M = Ti, Zr, Hf; R = t-Bu, Ph) by PhNMe2H+[B(C6F5)4]- to give [(η5-C5Me5){η5-C5H4CMe2CMe2C(R)═NH-κN}MCl]+[B(C6F5)4]- or by chloride ligand abstraction from the complexes [(η5-C5Me5)(η5-C5H4CMe2CH2C5H4N)MCl2] (M = Ti, Zr) by Li[B(C6F5)4]·2.5Et2O to give [(η5-C5Me5)(η5-C5H4CMe2CH2C5H4N-κN)MCl]+[B(C6F5)4]-. Solid state structures of the new compounds were established by X-ray diffraction analysis, and their electrochemical behavior was studied by cyclic voltammetry. The cationic complexes of Zr and Hf, compared to the corresponding neutral species, exhibited significantly enhanced luminescence predominantly from triplet ligand-to-metal (3LMCT) excited states with lifetimes up to 62 μs and quantum yields up to 58% in the solid state. DFT calculations were performed to explain the structural features and optical and electrochemical properties of the complexes.

Catalytic hydrodehalogenation (HDH) of aliphatic organohalides such as trifluorotoluenes by Et3SiH proceeds in the presence of readily available group 4 metal compounds: Cp'2MX2 (Cp' = η5-C5H5 or η5-C5Me5; X = F, Cl, or Me; M = Ti, Zr, or Hf), CpTiCl3 and TiCl4 with a catalytic amount of B(C6F5)3. The use of metallocenes in combination with the borane activator leads to a better selectivity of the reaction, i.e., suppression of Friedel-Crafts alkylations of arenes.

Photosensitizers, which produce singlet oxygen O2(1Δg) under light irradiation, have attracted much attention due to their application potential in medicine and material science. In this respect, we recently reported on cationic metallocene complexes with pendant N-donor moieties, which exhibited enhanced luminescence in the solid-state originating from their triplet states with luminescence quantum yields, ΦL, up to approximately 0.52, unprecedented for this class of compounds. This finding suggested that these complexes can be efficient singlet oxygen photosensitizers. Herein, we evaluate the photogeneration of O2(1Δg) by several Ti, Zr and Hf metallocenes in dichloromethane solution, including recently described cationic derivatives. After excitation by UV A light, cationic Zr and Hf metallocenes stabilized by N-donor imine and pyridine moieties exhibited green, yellow or orange luminescence from long-lived 3LMCT excited states (ΦL ∼ 0.02 – 0.40 in argon-saturated solutions) and efficient O2(1Δg) production (ΦΔ ∼ 0.29 – 0.77 in air-saturated solutions). In contrast, parent neutral Zr complexes and cationic Ti derivatives with enhanced absorption of visible light, exhibited lesser ability to produce O2(1Δg) (ΦΔ

A series of hybrid catalysts of the type, support-ligand-Pd (Sup-L-Pd), has been prepared and characterized and their activity in C-C coupling (Suzuki-Miyaura), selective oxidations and dehalogenation‑hydrogenation processes studied. The hybrid Sup-L-Pd catalysts are made up of (i) different nano-sized supports, such as halloysite nanotubes (HNTs), SiO2, Al2O3 and mesoporous silica nanoparticles (MSNs), (ii) ligands (L) with N-, S- or P-donor atoms and (iii) different quantities of Pd. Several combinations of support, ligand, and Pd quantity were used to determine the optimal composition of the nanostructured systems for the proposed catalytic reactions. The system based on HNTs functionalized with 2-(diphenylphosphino)ethyltriethoxysilane (PPETS) and 0.25% wt. Pd (HNTs-PPETS-Pd0.25) showed the most promising catalytic behaviour with multifunctional applicability in different catalytic processes and potential reusability. This catalyst gave turnover frequency (TOF) values of up to 155 h−1 in catalytic Suzuki-Miyaura C-C coupling reactions, up to 43 h−1 in selective catalytic oxidations and up to 65 h−1 in dehalogenation‑hydrogenation processes of halogenated aromatic compounds. Furthermore, the system demonstrated in the different catalytic reactions, good recyclability after consecutive cycles with low Pd leaching.

A family of ferrocene derivatives of the general formula [Fe(η5-C5H4CH2(p-C6H4)CH2(N-het))2] bearing saturated six- and five-membered N-heterocycles (N-het) was prepared. Reactions of the selected complexes with acids (HCl, acetic acid) afforded either the corresponding hydrochlorides or led to deprotection of the functionalized pendant N-heterocycles. The reaction of [{Ru(η6-p-cymene)Cl2}2] with the corresponding cyclopentadienide derivatives afforded cationic ruthenium complexes [Ru(η6-p-cymene)(η5-C5H4CH2(p-C6H4)CH2(N-het))]Cl while ruthenocenes [Ru(η5-C5H4CH2(p-C6H4)CH2(N-het))2] were formed as minor byproducts. The prepared complexes (20 examples) were characterized by elemental analysis, melting point, NMR and ESI-MS and the molecular structures of selected ferrocene derivatives were determined by X-ray diffraction analysis. The ferrocene derivatives and the ruthenium complexes were tested in vitro for their cytotoxic properties against three cell lines derived from ovarian cancer (A2780, A2780cis, and SK-OV-3) and against non-tumour embryonic cell line HEK293 (human kidney cells). The most active ferrocene derivatives displayed cytotoxicity in submicromolar and low micromolar concentration against both cisplatin (CisPt) sensitive and resistant cells. The results showed a significant effect of the pendant N-heterocycle on the ferrocene derivative toxicity and selectivity against cancer cells. Ultimately, ferrocene derivatives bearing either piperidine or morpholine groups were proposed to be the most promising substitutes for platinum drugs, as they exhibited comparable or even higher activity (in comparison to CisPt) against cancer cells, whereas these compounds were found to exhibit lower toxicity against embryonic HEK293 cells.

The role of the ketimide ligand geometry in Ti half-sandwich complexes and the consequent effects in olefin polymerization catalysis (ethylene, styrene, 1-hexene polymerization, and ethylene/1-hexene copolymerization) were investigated under various conditions. [CpTiCl2(N=CtBu2)] (1; Cp=η5-cyclopentadienyl) was used as a reference compound for comparison with the recently described complex [{η5-C5H4CMe2CMe2C(tBu)=N-κN}TiCl2] (2 a) and a new derivative that has a longer linker between Cp and the ketimide, [{η5-C5H4CH2CH2CMe2C(tBu)=N-κN}TiCl2] (9). The presence of a distorted intramolecularly tethered ketimide moiety reduces the polymerization activity significantly in systems that contain Al-based cocatalysts (methylaluminoxane, triisobutylaluminum). However, in Al-free systems both types of compounds provided active polymerization catalysts. Notably, the recently reported activation system Et3SiH/B(C6F5)3 was for the first time demonstrated to activate Ti complexes for ethylene and 1-hexene (co)polymerization catalysis by hydride transfer.

Scandium and yttrium half-sandwich chloride complexes (η5-C5Me4R)ScCl2(THF)2 R = CH2Ph (3) or SiMe2CH2CH2Ph (5) and (η5-C5Me4R)YCl2(THF)2 R = CH2Ph (4) or SiMe2CH2CH2Ph (6) were prepared by metathetic reactions of the corresponding substituted lithium or potassium cyclopentadienides with scandium or yttrium trichloride. A mutual comparison of the determined solid state structures of 4 and 5 revealed the tetranuclear character in the case of scandium complex containing C5Me4SiMe2CH2CH2Ph ligand, while a formation of the trinuclear ate-complex 4 incorporating lithium was observed for the combination of yttrium and the benzyl substituted tetramethyl cyclopentadienyl. Moreover, the steric effect of addition of another differently substituted cyclopentadienyl ring into the molecule was evaluated.

A pendant nitrile group attached to the lithium cyclopentadienide moiety in (C5H4CMe2CMe2CN)Li was alkylated using organyl lithium reagents (RLi, R = Ph, t-Bu, Me), giving rise to dianionic cyclopentadienyl-ketimides [C5H4CMe2CMe2C(R)═N]Li2, which were subsequently utilized as chelating ligands for the synthesis of group 4 bent metallocene or half-sandwich complexes (12 examples of the types [(η5-C5R′5){η5-C5H4CMe2CMe2C(R)═N-κN}MCl], R′ = H or Me, M = Ti, Zr, or Hf, and [{η5-C5H4CMe2CMe2C(R)═N-κN}TiX2], X = Cl or NMe2, respectively, were prepared and characterized). Consecutive protolysis of the intramolecularly bound ketimide moiety in bent metallocenes afforded pendant imine or cationic iminium moieties, respectively, attached to group 4 organometallic fragments. Selected compounds were used as precatalysts in a preliminary screening for ethylene polymerization activity.

C20H27ClN2OTi, monoclinic, P21/c (no. 14), a = 9.4006(2) Å, b = 10.8185(3) Å, c = 19.4821(5) Å, β = 97.941(1)°, V = 1962.34(9) Å3, Z = 4, R gt(F) = 0.0270, wR ref(F 2) = 0.0731, T = 150(2) K.

Several approaches to the intramolecular activation of a pendant nitrile group attached to the group 4 metallocene framework have been probed starting with the complexes [(η5-C5Me5)(η5-C5H4CMe2CH2CN)MCl2] (M = Zr, 1; M = Ti, 2). A reduction induced activation of the nitrile moiety was effected for the Zr derivative either by the treatment with Mg, or by the alkylation using t-BuMgCl followed by spontaneous reductive elimination. In both cases, the reactions finally yielded the zirconocene cyano complex with an intramolecularly tethered alkyl substituent, [(η5-C5Me5)(η5:κC1-C5H4CMe2CH2)Zr(CN-κC)] (4), which resulted from the C–C bond cleavage in the pendant arm. Furthermore, a by-product was isolated which contained two zirconocene fragments bridged through a MgCl2 moiety featuring a rare σ,π-bridging mode of the pendant nitrile group, [{(η5-C5Me5)(μ-η5:η2:κN-C5H4CMe2CH2CN)(μ-Cl)Zr}2Mg] (3). The solid-state structure of 3 was elucidated and this compound together with the product 4 and the tentative intermediate [{(η5-C5Me5)(η5:η2-C5H4CMe2CH2CN)Zr] (3′) were also investigated by DFT calculations. In another approach, 1 and 2 were treated with Li[B(C6F5)4]∙Et2O to generate cationic complexes. Accidental hydrolysis of these species afforded complexes bearing an intramolecularly tethered amide group [{(η5-C5Me5)(η5:κO-C5H4CMe2CH2CONH2)M], of which the Ti derivative (6) was isolated and structurally characterised. Finally, reaction of the zirconocene dimethyl complex [(η5-C5Me5)(η5-C5H4CMe2CH2CN)ZrMe2] (8) with (Ph3C)[B(C6F5)4] was studied.

Functional groups attached to η 5 -coordinated cyclopentadienyl or related (indenyl, fluorenyl) ligands in transition metal complexes may be subjected to various synthetic transformations giving rise to novel, often otherwise inaccessible organometallic derivatives. Alternatively, this approach may eliminate the necessity of previous elaborate ligand synthesis. A number of synthetic methods have appeared in the recent past, which are compatible even with reactive electrophilic early transition metal compounds. This review article summarizes the development of functional group chemistry performed at group 4 metallocene, half-sandwich, and related complexes.

A series of tetramethyl-(Cp′) and pentamethylcyclopentadienyl (Cp*) metal complexes (η5-C5Me4R)ZrCl2LCO (R = H(1), Me(2)) and (η5-C5Me4R)HfCl2LCO (R = H(3), Me(4)) where LCO is a bifunctional β-diketiminate ligand [2-(MeO)–C6H4)]NC(Me)CHC(Me)N[2-(MeO)–C6H4)] (LCO) were prepared from corresponding tetramethyl- and (pentamethylcyclopentadienyl)metal trichlorides and the lithium precursor LiLCO. All complexes were characterized by their melting point, elemental analysis, 1H and 13C NMR spectroscopy, IR spectroscopy. In addition their solid-state structures were determined by X-ray diffraction techniques. In all cases, a pseudo-tetragonal pyramidal coordination environment of the metal centre with cyclopentadienyl ligand on the top and nearly isobidentately bonded nitrogen atoms of the chelating LCO ligand in an open η5-fashion was observed. The oxygen atoms positioned at the diketiminate periphery remained uncoordinated to transition metal in the solid phase as well as in solution. Besides the desired compounds, two hafnium complexes bearing either 2-methoxyaniline or 2-methoxyanilide ligands were isolated and structurally characterized as minor decomposition and dismutation products of 3 and 4, respectively. Complexes containing the β-diketiminate ligand as well as its precursors were tested for catalytic activity in the polymerization of ethylene using different activators (MAO, MMAO and AliBu3/(Ph3C)+ [B(C6F5)4]−). Among the new complexes, the best activity as high as 340 kgPE (molMhbar)−1 was achieved with 1/AliBu3/(Ph3C)+ [B(C6F5)4]− system. In attempts to clarify the activation process of group 4 metal-based precatalysts, the synthesis and NMR studies of the aluminium β-diketiminate complex Al(iBu)2LCO were also carried out.

Cyclopentadienyl-arene complexes [(η 5 -C 5 H 4 CMe 2 Ph)Ti(O i Pr) 3 ] ( 2 ) and [(η 5 -C 5 H 4 CMePh(CH 2 CH 2 CH CH 2 ))Ti(O i Pr) 3 ] ( 3 ), where Me = methyl, Ph = phenyl, i Pr = isopropyl, were prepared and characterized by spectroscopic methods (NMR, IR, ESI-MS) and elemental analysis (EA). 2 was anchored on two siliceous supports SiO 2 and SBA-15 (pre-treated at 200, 700, and 800 °C) predominantly by a covalent Ti–O–Si bond. 3 was grafted onto SiMe 2 H-modified silica by hydrosilylation at 25 and 90 °C. 3 was attached by a flexible covalent tether –(CH 2 ) 4 SiMe 2 – from the ligand to the silica surface. Models for immobilized surface species [(η 5 -C 5 H 4 CMe 2 Ph)Ti(POSS-O 3 )] ( 4 ) (where POSS-O 3 = open silsesquioxane) and [(η 5 -C 5 H 4 {CMePh(CH 2 ) 4 SiMe 2 OSi(O t Bu) 3 })Ti(O i Pr) 3 ] ( 6 ) (where t Bu = tertiary butyl) were also prepared and characterized. Comparison of homogenous catalysts 1 – 4 and 6 /MAO (where 1 = [(η 5 -C 5 H 4 CMe 2 Ph)TiCl 3 ]; MAO = methylaluminoxane) for ethylene trimerization showed that activity was influenced mainly by the σ-ligand. The alkyl (R) substituent of CMePhR had a negligible effect. Activity of the heterogeneous 2 /support/MAO catalyst increased with increasing pre-treatment temperature (i.e. decreasing amounts of residual surface silanol groups). However, the leaching test showed, that a significant activity could be attributed to an active species leached from the support. We propose that an easy cleavage (methylation) of Ti–O–Si linkage by an excess of MAO would be the main origin of leaching. The inactivity of 3 /support/MAO towards ethylene trimerization was attributed to close contact between the catalytically-active species and the surface.

The reactivity of substituted half-sandwich complexes of Ti, Zr, and Hf towards 2,6-diisopropylaniline NH2C6H3-2,6-iPr2 (LNH) and 2-[(dimethylamino)methyl]aniline NH2C6H4-2-(CH2NMe2) (LNNH) was investigated. Two series of mononuclear complexes (η5-C5Me5)LNMCl2 (M = Ti (3), Zr (4), Hf (5)) and (η5-C5Me5)LNNMCl2 (M = Ti (7), Zr (8), Hf (9)) were prepared from corresponding (pentamethylcyclopentadienyl)metal trichlorides and the lithium precursors LNLi and LNNLi. Besides the desired products a dimeric hafnium compound [(η5-C5Me5){µ-NC6H4-2-(CH2NMe2)}HfCl]2 (10) was also isolated and structurally characterized. The formation of dimeric complexes of this type was also achieved by reacting a series of (η5-C5Me4R)LCNMCl2 (M = Zr, Hf; R = Me, H; LCN = C6H4-2-(CH2NMe2)-µ2C,N) complexes with lithium precursors LNLi and LNNLi generating [(η5-C5Me4H){µ-NC6H3-2,6-iPr2}MCl]2 (M = Zr (11), Hf (13)), [(η5-C5Me5){µ-NC6H3-2,6-iPr2}MCl]2 (M = Zr (12), Hf (14)), [(η5-C5Me4H){µ-NC6H4-2-(CH2NMe2)-µ2N,N}ZrCl]2 (15), and [(η5-C5Me5){µ-NC6H4-2-(CH2NMe2)}ZrCl]2 (16), respectively. The formation of 10 by this reaction procedure was not detected; instead monomeric complexes (η5-C5Me4R)LNNLCNHfCl (R = H (17), Me (18)) were observed as major products. NMR and IR spectroscopy techniques and elemental analysis were used for characterization of the prepared complexes, whereas the structures in most cases were determined by X-ray crystallography.

Ferrocenes represent an interesting group of drugs with potential antitumor properties. Moreover, their electronic properties make them suitable for electrochemical studies. We determined an uptake of a novel ferrocene derivative in low μM concentrations by selected cancer cell lines and showed its localization predominantly in cytoplasm, using glassy carbon electrodes.

Titanocene dichlorides of general formula [(η5-C5H5)(η5-C5H4R)TiCl2] (where R = 5-deoxy-1,2-di-O-isopropylidene-3-O-benzyl-α-d-xylofuranos-5-yl (Xylf) (8a); R = 5-deoxy-1,2-di-O-isopropylidene-3-O-benzyl-α-d-ribofuranos-5-yl (Ribf) (8b)) and [(η5-C5H4R)2TiCl2] (R = Xylf (9a); R = Ribf (9b)) were prepared by reaction of the corresponding lithium cyclopentadienides 7a,b with an equimolar amount of [(η5-C5H5)TiCl3] or a 0.5 mol amount of [TiCl4(THF)2]. Titanocene difluorides of the general formula [(η5-C5H4R1)(η5-C5H4R2)TiF2] (R1 = H and R2 = Ribf (10); R1 = R2 = Xylf (11a); R1 = R2 = Ribf (11b)) were obtained by fluorination of the corresponding titanocene dichlorides 8b and 9 with the fluorinating agent {2-(CH2NMe2)C6H4-κC,N}(n-Bu)2SnF in high yields. Alternatively, complexes 11 were prepared in a straightforward way by direct reaction of [TiF4(THF)2] with 2 equiv of the corresponding lithium cyclopentadienide 7a,b. Ferrocene complexes [(η5-C5H4R)2Fe] (R = Xylf (12a); R = Ribf (12b)) were synthesized by me...

New titanocene dihydrosulfide compounds [(C 5 Me 4 CH 2 Ph) 2 Ti(SH) 2 ] ( 6 ) and [(C 5 Me 4 t -Bu) 2 Ti(SH) 2 ] ( 7 ) were obtained by addition of hydrogen sulfide to the corresponding doubly tucked-in titanocenes, and titanocene hydrosulfide compounds [(C 5 Me 4 CH 2 Ph) 2 TiSH] ( 8 ) and [(C 5 Me 4 t -Bu) 2 TiSH] ( 9 ) by H 2 S-induced protonolysis of σ-Ti–C bonds in [(η 5 -C 5 Me 4 CH 2 Ph)Ti(III)(η 5 :η 1 -C 5 Me 4 CH 2 - o -C 6 H 4 )] and [(C 5 Me 4 t -Bu)Ti(III)(η 5 :η 1 -C 5 Me 4 CMe 2 CH 2 )], respectively. The crystal structures of 6 , 8 , and 9 and electronic absorption spectra of 6 – 9 in hexane solution highly resemble those of corresponding [Cp* 2 Ti(SH) 2 ] ( 1 ) and [Cp* 2 TiSH] ( 2 ), however, compounds 6 and 7 strongly differ in their sensitivity to sunlight mutually and with respect to 1 . The sunlight photolysis of 6 in toluene proceeded similarly to the process described previously for 1 except that about three times longer exposition (300 h) was required to obtain the cyclopentadienyltitanium sulfide cage cluster [{(C 5 Me 4 CH 2 Ph)Ti} 4 S 6 ] ( 10 ) in 48% yield. In contrast, compound 7 photo-decomposed very efficiently to give compound 9 as the only isolated titanium-containing product in 87% yield. The formation of 10 can be accounted for the redox elimination of the cyclopentadiene followed by elimination of hydrogen sulfide in intramolecular condensation reaction whereas the formation of 9 requires the dissociation of SH radicals. Both the processes were recognized by Rosenthal and Beweries to concur in photodecomposition of [Cp* 2 Ti(OH) 2 ].

The reaction of [Cp(η5-C5H4CH2SiMe2H)TiCl2] (1; Cp = η5-C5H5) and methanol in the presence of catalytic amounts of B(C6F5)3 afforded a complex with a pendant silyl ether group, [Cp(η5-C5H4CH2SiMe2OMe)TiCl2] (2), in good yield. The analogous reaction of 1 and Ph3COH resulted in the unexpected formation of [CpTiCl2{μ-η5:η5-(C5H4)CH2SiMe2OSiMe2CH2(C5H4)}TiCl2Cp] (4). The formation of siloxanes from the reaction of 2 equiv of hydrosilane with Ph3COH mediated by B(C6F5)3 has a general applicability and proceeds in two consecutive steps: (i) transfer of the hydroxyl group from the trityl moiety to the silicon atom and (ii) silylation of the silanol formed in situ with the second equivalent of hydrosilane. The different hydrosilane reactivity toward Ph3COH in comparison with other alcohols can be attributed to the easy generation of the borate salt [Ph3C]+[(C6F5)3B(μ-OH)B(C6F5)3]− (5) under catalytic conditions. The intramolecular Si–H and Ti–Cl exchange in 1 is catalyzed by B(C6F5)3 in the presence of no alcoho...

The novel Co(I)-complex [CpCNCo(COD)] (CpCN = η5-(C5H4CMe2CH2CN), COD = 1,5-cyclooctadiene; 3) with a substituted cyclopentadienyl ligand containing a pendant nitrile moiety has been synthesized an...

Catalytic activity of CuBTC and FeBTC was investigated in Beckmann rearrangement of a series of aromatic and non-aromatic oximes and compared with that of zeolites Beta and USY. The reactivity of substrates in Beckmann rearrangement increases in the order camphor oxime

Hydrosilane-B(C6F5)3 adducts were found to activate zirconocene dihalides and generate ternary catalytic systems possessing moderate to high activity in ethylene polymerization to high density polyethylene (HDPE). The activation efficacy of the adducts increased with increasing hydride donor ability and decreased with steric crowding of the particular hydrosilane used. NMR investigation of the HSiEt3/B(C6F5)3/Cp*2ZrF2 system (Cp* = η(5)-C5Me5) revealed the formation of a stable intermediate [Cp*2ZrF(FSiEt3-κF)](+)[HB(C6F5)3](-), whereas a crucial role of the [HB(C6F5)3](-) anion as a hydride donor for generation of an active cationic zirconium hydride center was elucidated.

The series of half-sandwich metallocenes of group 4 metals containing the C,N-chelating ligand (η5-C5Me4R)MCl2(C6H4CH2NMe2-κ2C,N) (M = Ti(1), Zr(2), Hf(3); R = Me(C), H(D)) were prepared by reacting the corresponding pentamethyl- and tetramethyl-substituted cyclopentadienylmetal trichlorides (η5-C5Me4R)MCl3 (M = Ti(1), Zr(2), Hf(3); R = Me(A), H(B)) with 2-[(dimethylamino)methyl]phenyl lithium. The X-ray crystal structure analysis of 1C–3C showed that they are isostructural/isomorphous containing two pairs of enantiomers in a P21/c unit cell, whereas crystals of 2D and 3D contained only one enantiomer in a P212121 unit cell. The presence of enantiomers in solution was resolved in variable temperature 1H NMR spectra below the temperature of signal coalescence. The transition state for interconversion of the two enantiomers for 1C was identified by DFT results to be on a 2nd order saddle point. Synthesis of η5-tetramethylcyclopentadienylmetal trichlorides 2B and 3B and their tetrameric and dimeric crystal structures are also reported.

The diphenyl zirconocene [(η5-C5H5){η5-C5H4CMe2(CH2)2CH CH2}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.

The preparation of a new functionalized cyclopentadienyl ligand bearing a nitrile pendant substituent, (C 5 H 4 CMe 2 CH 2 CN) − is reported. The corresponding lithium salt of this ligand ( 1 ) was prepared by the reaction of in situ lithiated acetonitrile with 6,6-dimethylfulvene. The ligand was subsequently utilized for the synthesis of group 4 metal complexes [(η 5 –C 5 H 4 CMe 2 CH 2 CN) 2 MCl 2 ] (M = Ti, 2 ; M = Zr, 3 ; M = Hf, 4 ), [(η 5 –C 5 H 5 ) (η 5 –C 5 H 4 CMe 2 CH 2 CN)MCl 2 ] (M = Ti, 7 ; M = Zr, 8 ), and [(η 5 -C 5 Me 5 ) (η 5 C 5 H 4 CMe 2 CH 2 CN) 2 ZrCl 2 ] ( 9 ). Alternative route to 2 comprised the preparation of half-sandwich complex [(η 5 –C 5 H 4 CMe 2 CH 2 CN)TiCl 3 ] ( 6 ). The prepared compounds were characterized by common spectroscopic methods and the solid state structures of complexes 2 , 3 , 4 , 7 , and 9 were determined by the single-crystal X-ray diffraction analysis. In addition, compound 7 was converted to the corresponding dimethyl derivative [(η 5 –C 5 H 5 ) (η 5 –C 5 H 4 CMe 2 CH 2 CN)TiMe 2 ] ( 10 ) and also treated with the chloride anion abstractor Li[B(C 6 F 5 ) 4 ] to generate the cationic complex with the coordinated nitrile group, as suggested by the NMR spectroscopy. A formation of yet another cationic complex was observed upon treating compound 10 with (Ph 3 C)[B(C 6 F 5 ) 4 ].

New heterogeneous catalysts for ring opening metathesis polymerization (ROMP) have been prepared by immobilization of RuCl2(p-cymene)(PCy3) (Cy = cyclohexyl) on silica and siliceous mesoporous molecular sieves SBA-15 and MCM-41. Activity of these catalysts was investigated in ROMP of norbornene (NBE) and its derivatives (dicyclopentadiene, 5-norbornene-2-yl acetate). High molecular weight polymers (Mw up to 400 000) were prepared in yields up to 80% using catalysts based on mesoporous sieves. In contrast, with catalyst based on conventional silica the yield did not exceed 28% (ROMP of NBE). Filtration test proved that the catalytic activity was bound to the solid phase. Catalysts could be easily separated from the reaction mixture in contrast to the corresponding homogeneous system. Therefore, polymers with reduced amounts of catalyst residues were obtained.

The reaction of in situ generated 1′-(diphenylphosphino)-1-lithioferrocene with isocyanates RNCO affords the respective phosphino-carboxamides Ph2PfcCONHR (fc = ferrocene-1,1′-diyl, R = cyclohexyl (2), and Ph (3)) in moderate yields. The coordination behaviour of 3 chosen as a representative was studied in palladium(II) and platinum(II) complexes. Depending on the metal precursor and the reaction conditions, the following compounds featuring this ligand as a P-monodentate or an O,P-chelating donor were isolated and characterised by spectroscopic methods (IR, multinuclear NMR and electrospray ionisation MS): trans-[PdCl2(3-κP)2] (5), trans-[PtCl2(3-κP)2] (6), cis-[PtCl2(3-κP)2] (7), [SP-4-4]-[(LNC)PdCl(3-κP)] (8; LNC = 2-[(dimethylamino-κN)methyl]phenyl-κC1), and [SP-4-3]-[(LNC)PdCl(3-κ2O,P)]SbF6 (9). Besides, the crystal structures of a phosphine oxide resulting by oxidation of 2, viz Ph2P(O)fcCONHCy (4), and of complexes 5·2Et2O and 9 have been determined by single-crystal X-ray diffraction analysis.

Alkyne under stress: a novel metallacycle containing one Zr atom, two Si atoms, and a C≡C bond has been prepared and its structure elucidated (Zr green, Si blue, C gray). According to X-ray data, spectral properties, and DFT calculations, the bonding situation in this compound is characterized as a 1-metalla-2,5-disilacyclopent-3-yne with a weak metal-triple-bond interaction.

The reactivity of variously substituted alkynylsilanes toward selected group 4 metallocene complexes was investigated. Reactions of the alkynylsilanes R(1)C(2)SiR(2)(2)H (R(1) = SiMe(3), R(2) = Me, 1; R(1) = SiMe(3), R(2) = Ph, 2; R(1) = SiMe(2)H, R(2) = Me, 5) with Cp(2)TiMe(2) (Cp = eta(5)-cyclopentadienyl) resulted, upon methyl group transfer to the silyl group, in the previously described titanocene alkyne complexes Cp(2)Ti(R(1)C(2)SiR(2)(2)R(3)) (R(1) = Me(3)Si, R(2) = R(3) = Me, 3; R(1) = HMe(2)Si, R(2) = R(3) = Me, 6) or the unreported complex 4 (R(1) = Me(3)Si, R(2) = Ph, R(3) = Me). The Cp(2)TiCl(2)/n-BuLi system yielded alkyne complexes 6 and 7 (R(1) = HMe(2)Si, R(2) = Me, R(3) = H); no alkyl group transfer was detected. On the other hand, reactions utilizing the Cp(2)ZrCl(2)/n-BuLi system afforded inseparable mixtures; however, complexes of the type Cp(2)Zr[R(1)C(2)SiMe(2)(n-Bu)] (R(1) = Me(3)Si, 8; R(1) = HMe(2)Si, 9) were detected. Cp(2)Hf(n-Bu)(2) reacted with the alkynylsilanes in a diverse way, depending on the substituents of the alkyne substrate. The reaction with an excess of alkyne 1 (R(1) = Me(3)Si, R(2) = Me) afforded only an intractable mixture, which contained Me(3)SiC(2)SiMe(2)(n-Bu) (10). Hafnacyclopentadienes 13-15 as precedented product types were obtained when alkyne 12 (R(1) = Ph, R(2) = Me) was used. In sharp contrast, the symmetrically substituted alkynes 5 (R(1) = HMe(2)Si, R(2) = Me) and H(2)PhSiC(2)SiPhH(2) (18) yielded the hitherto unknown Si-containing metallacycles 16 and 19. A reaction mechanism leading to these products was proposed and subsequently supported by DFT calculations. In addition, the reduction of Cp(2)HfCl(2) with magnesium in THF in the presence of alkynylsilanes was shown to be an alternative route to compounds 14-16 and 19. Presumably due to steric reasons, alkyne 1 could not form any of the product types described above. Nevertheless, it was utilized for the preparation of the PMe(3)-stabilized hafnocene alkyne complex 11.

(Ferrocenylmethyl)(2-hydroxyethyl)amine ( 1 ) reacts with mono- (CH 3 CO 2 H and PhCO 2 H) and dicarboxylic acids (HO 2 C(CH 2 ) n CO 2 H ( n = 0–2), ( E )- and ( Z )-HO 2 CCH CHCO 2 H) to give the respective carboxylates, viz [ 1 H](RCO 2 ) ( 2 , R = CH 3 ; 3 , R = Ph), [ 1 H] 2 (O 2 C(CH 2 ) n CO 2 ) ( 4 , n = 0; 5 , n = 1; 6 , n = 2), [ 1 H] 2 (( E )-O 2 CCH CHCO 2 ) ( 7 ) and [ 1 H] 2 (( Z )-HO 2 CCH CHCO 2 ) ( 8 ), as defined crystalline solids. Crystal structures of 2 – 8 have been determined by single-crystal X-ray diffraction analysis, revealing extensive hydrogen bonding interactions based predominantly on charge-supported N + –H···O − and O–H···O − hydrogen bonds, and on C–H···O contacts. Whereas the crystal assemblies of the monocarboxylate salts propagate preferentially in one dimension ( 2 : cross-linked chains, 3 : columnar stacks), those of the salts prepared from the dicarboxylic acids (including hydrogenmaleate 8 ) are best described as layered composite arrays resulting via alternation of polar, hydrogen-bonded layers and of non-polar sheets constituted by the ferrocenyl substituents.

Interaction of (Sp)-2-(diphenylphosphino)ferrocenecarboxylic acid [(Sp)-1] with N,N′-dicyclohexylcarbodiimide (DCC) and N-ethyl-N′-[3-(dimethylamino)propyl]carbodiimide (EDC) have been investigated in order to study the reacting system itself and to characterise side-products typically arising during the diimide-promoted condensation of acid (Sp)-1 with nucleophiles. The reaction between (Sp)-1 and DCC was found to give preferentially the respective urea derivative in the absence of a base, and (Sp)-2-(diphenylphosphino)ferrocenecarboxylic anhydride [(Sp,Sp)-3] when the same reaction was performed in the presence of 4-(dimethylamino)pyridine (DMAP). With EDC, the preference for a reaction pathway was less pronounced: whereas the reaction without the base afforded exclusively the corresponding urea, that in the presence of DMAP yielded a mixture of the urea and anhydride (Sp,Sp)-3.

Ferrocene-based β-aminoalcohols FcCH 2 NHCR 2 CH 2 OH (R = H, 1a ; R = Me, 1b ) and ( S )-FcCH 2 NHCH(CHMe 2 )CH 2 OH ( 1c ; Fc = ferrocenyl) react with 2,4,6-trinitrophenol (Hpic) under proton transfer to afford the corresponding ammonium picrates 2a – c . In the crystal, these picrates associate predominantly via N–H⋯O and O–H⋯O bifurcated hydrogen bonds between the NH 2 + and OH groups in the aminoalcohol chain as the donors and the phenoxide and NO 2 oxygen atoms of the picrate anion as the acceptors. Compounds 2a and 2b form closed dimeric assemblies [ 1n H] 2 [pic] 2 ( n = a , b ) around the crystallographic inversion centres. By contrast, their chiral analogue 2c gives rise to monomeric units [ 1c H][pic] (albeit through similar interactions), that further aggregate into infinite linear chains via N–H⋯O hydrogen bonds. The formed assemblies are interconnected by the soft C–H⋯O hydrogen bonds and via π⋯π stacking interactions of the picrate ions.

1′-(Diphenylphosphino)-1-(N-butylcarbamoyl)ferrocene (P1) and the analogous higher amides P2–4 related to the first-generation PAMAM dendrimers bearing up to four 1′-(diphenylphosphino)ferrocen-1-yl terminal groups were synthesized by amidation of the respective (poly)amines with 1′-(diphenylphosphino)ferrocenecarboxylic acid (Hdpf). Testing of amides P1–4 as ligands for palladium-catalyzed Suzuki and Heck coupling reactions has shown that these amidophosphines preserve the activity of the single phosphinoferrocenyl unit, giving rise to active catalysts in both C–C forming reactions. Even for such relatively small systems, a positive influence of the dendritic assembly was notable as the compounds bearing a higher number of the phosphinoferrocenyl termini afforded faster reacting catalytic systems at the same palladium loading and P-to-Pd ratio.

Planar chiral alkenylferrocene phosphanes, viz. ( S p )-[Fe(η 5 -C 5 H 3 -1-PPh 2 -2-CH CR 2 )(η 5 -C 5 H 5 )] (R = H, ( S p )- 2 ; Ph, ( S p )- 5 ) and ( S p )-[Fe(η 5 -C 5 H 3 -1-PPh 2 -2-( E )-CH CHR)(η 5 -C 5 H 5 )] (R = Ph, ( S p )- 3 ; C(O)CH 3 , ( S p )- 6 ; and CO 2 CH 2 CH 3 , ( S p )- 7 ) have been prepared by alkenylation of ( S p )-2-(diphenylphosphanyl)ferrocenecarboxaldehyde and tested as ligands for enantioselective palladium-catalysed allylic alkylation of 1,3-diphenyprop-2-en-1-yl acetate with dimethyl malonate. All phosphanylalkenes formed active catalysts. However, the induced enantioselectivity was only poor to moderate [12–43% ee after 20 h at room temperature], with the ee’s and configuration of the preferred product strongly depending on the ligand structure. The catalytic results have been related to solution properties (NMR, ESI MS) and the solid-state structural data (X-ray diffraction) of [Pd(η 3 -1,3-Ph 2 C 3 H 3 ){( S p )- 2 -η 2 :κ P }]ClO 4 (( S p )- 12 ), which represent a model of the plausible reaction intermediate.

A series of copper(I) and silver(I) carboxylates received from various ferrocenecarboxylic acids was synthesized and used in the preparation of heterooligometallic Ti–Cu(Ag)–Fe complexes. The silver(I) salts [FcCO2Ag] (2a) and [FcCH CHCO2Ag] (2b) (Fc = ferrocenyl, (η5-C5H4)Fe(η5-C5H5)) were obtained through deprotonation of the respective acids FcCO2H (1a) and FcCH CHCO2H (1b) with NEt3, followed by a reaction with [AgNO3]. The heterotrimetallic complexes {[Ti](μ-σ,π-C CSiMe3)2}AgO2CFc (4a) and {[Ti](μ-σ,π-C CSiMe3)2}AgO2CCH CHFc (4b), where [Ti] denotes the (η5-C5H4SiMe3)2Ti unit, were obtained from the reaction of 2a and 2b with the organometallic π-tweezer compound [Ti](C CSiMe3)2 (3). The related heterotrimetallic copper(I) complex {[Ti](μ-σ,π-C CSiMe3)2}CuO2CFc (9a) was prepared via two synthetic routes. First, salt 2a was reacted with [(η2-Me3SiC CSiMe3)CuBr]2 (10) to give the alkyne-stabilized copper(I) carboxylate [(η2-Me3SiC CSiMe3)(CuO2CFc)2]2 (11). Subsequent reaction of 11 with four equivalents of 3 afforded 9a. Alternatively, 9a and its analogues {[Ti](μ-σ,π-C CSiMe3)2}CuO2C–E–Fc (E = trans-CH CH (9b), CH2CH2 (9c)), were prepared from acidolysis of the Cu–CMe bond in {[Ti](μ-σ,π-C CSiMe3)2}CuMe (8) with acids 1a–1c. An analogous reaction between HO2CfcPPh2M(CO)5 (M = Cr (14a), Mo (14b), W (14c); fc = ferrocene-1,1′-diyl) and 8 at−30 °C gave the alkyne/ferrocene-bridged heterotetrametallic compounds {[Ti](μ-σ,π-C CSiMe3)2}CuO2CfcPPh2M(CO)5 (M = Cr (15a), Mo (15b), W (15c)). Reversing the reaction steps so that {[Ti](μ-σ,π-C CSiMe3)2}CuO2CfcPPh2 (12) was prepared first and then reacted with M(CO)5(thf) (M = Cr (13a), Mo (13b), W (13a)) gave complicated reaction mixtures from which pure 15a–15c could not be isolated. The solid-state structures of 5, 7, 9a, and 11 have been corroborated by single-crystal X-ray structural studies and the electrochemical behavior of acids 1a–1c and of complexes 4a, 4b and 9a–9c was studied by cyclic voltammetry.

A series of phosphinoferrocene carboxamides bearing achiral (benzyl) and chiral [(R)- and (S)-1-phenylethyl] substituents at the amide nitrogen have been prepared from 1‘-(diphenylphosphino)ferrocenecarboxylic (Hdpf) and (Sp)-2-(diphenylphosphino)ferrocenecarboxylic ((Sp)-1) acids and tested as ligands for enantioselective allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate. At room temperature, the alkylation reactions proceeded with complete conversions and ee's up to 90%, the most efficient being the planar-only chiral ligand (Sp)-2-(diphenylphosphino)-1-(N-benzylcarbamoyl)ferrocene ((Sp)-2). The crystal structures of (Sp)-2 and the cationic (η3-allyl)palladium(II) complex [Pd(η3-1,3-Ph2C3H3){(Sp)-2-κ2O,P}]ClO4 ((Sp)-8) have been determined by single-crystal X-ray diffraction and solution NMR data were obtained to provide an insight into the mechanism of chiral discrimination.

The chiral ferrocene derivative (R,R p ) -2-[1-(diphenylphosphanyl)ethyl]ferrocenecarboxylic acid (1) is prepared together with selected derivatives resulting from modification at the phosphane moiety [P-oxide (5) and P-sulfide (4)] and the carboxyl group {amides bearing benzyl (6) and (R)- or (S)-1-phenylethyl substituents [(R)-7 and (S)-7] at the amide nitrogen atom}. Acid 1 and amide 6 are studied as ligands in rhodium and palladium complexes. Bridge cleavage of the dimer [{Rh(μ-Cl)Cl(η 5 -C 5 Me 5 )}2] with 1 gives [RhCl 2 (η 5 -C 5 Me 5 )(1-κP)] (9) containing P-monodentate 1, which undergoes smooth conversion to the (phosphanylalkyl)ferrocenecarboxylato complex [RhCl(η 5 -C 5 Me 5 ){Fe(η 5 -C 5 H 5 ](η 5 -C5H3-1-CH(Me)PPh2-2-COO-κ 2 O,P)] (10) upon treatment with silica gel or alumina. Yet another O,P-chelate complex, [Rh{Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 3 -1-CH(Me)PPh 2 -2-COO-κ 2 O,P}[CO)-(PCy 3 )] (11; Cy = cyclohexyl) is obtained directly by an acid-base reaction between the acetylacetonato complex [Rh(acac)(CO)(PCy 3 )] and 1. Amide 6 reacts with [{Pd(μ-Cl]-(η 3 -C 3 H 5 )} 2 ] to give the expected phosphane complex [PdCl(η 3 -C 3 H 5 )(6-κP)] (12), while the replacement of the cyclooctadiene (cod) ligand in [PdCl(Me)(cod)] affords the chelate complex [PdCl(Me)(6-κ 2 O,P)] (13). All compounds are characterised by spectroscopic methods and the solid-state structures of 5, 9, 11, 13, (R,S p )-2-[1-(diphenylphosphoryl)-ethyl]-1-[N-(R]-(1-phenylethyl)carbamoyl]ferrocene [(R)-8; phosphane oxide from (R)-7], and the synthetic precursors (R,S p )-1-bromo-2-[1- (diphenylphosphanyl)ethyl]ferrocene (2) and (R,S p ]-1-bromo-2-[1-(diphenylthiophosphoryl)ethyl]ferrocene (3) determined by single-crystal X-ray diffraction. The catalytic properties of 1 and the amides are probed in enanatioselective rhodium-catalysed hydrogenation and palladium-catalysed asymmetric allylic alkylation.

Treatment of racemic 1-(diphenylphosphanyl)-2-[(methoxycarbonyl)methyl]ferrocene successively with NaN(SiMe3)2 and methyl iodide affords the C-alkylated product, 1-(diphenylphosphanyl)-2-[1-(methoxycarbonyl)ethyl]ferrocene (6), as a mixture of diastereoisomers in ca. 10:1 ratio, from which the major (S,Rp/R,Sp)-diastereoisomer is easily isolated by crystallisation. (S,Rp/R,Sp)-6 reacts with [Pd(LNC)(MeCN)2]ClO4 (LNC = 2-[(dimethylamino-κN)- methyl]phenyl-κC1) to give the cationic bis-chelate complex (S,Rp/R,Sp)-[Pd(LNC)(6-κ2O,P)]- ClO4 (9). The structures of (S,Rp/R,Sp)-6 and 9 have been determined by single-crystal X-ray diffraction. Hydrolysis of ester 6 to the corresponding carboxylic acid proved to be difficult, being complicated by racemisation at the chiral carbon atom and oxidation of the phosphanyl group.

Functional groups attached to η 5 -coordinated cyclopentadienyl or related (indenyl, fluorenyl) ligands in transition metal complexes may be subjected to various synthetic transformations giving rise to novel, often otherwise inaccessible organometallic derivatives. Alternatively, this approach may eliminate the necessity of previous elaborate ligand synthesis. A number of synthetic methods have appeared in the recent past, which are compatible even with reactive electrophilic early transition metal compounds. This review article summarizes the development of functional group chemistry performed at group 4 metallocene, half-sandwich, and related complexes.