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The SEAr/SNAr reaction between 7-chloro-4,6-dinitrobenzofuroxan (ClDNBF) and 2-morpholinyl-, 2-piperidinyl-, or 2-pyrrolidinylthiazole afforded unexpectedly two isomeric products, bearing the benzofuroxanyl moiety bound to the C-5 carbon atom of the thiazole ring. The relative ratio for the two isomers was dependent on temperature and solvent, suggesting the occurrence of an equilibrium between the two novel species. In order to investigate their structure and to design a plausible mechanistic pathway, a series of synthetic and spectroscopic experiments was planned. The isomer's structure was unambigously assigned when the reduction of furoxanyl to the furazanyl ring of the products gave exclusively a single species whose NMR data were coincident with those obtained by reacting the starting 2-aminothiazole derivatives with the 7-chloro-4,6-dinitrobenzofurazan (ClDNBZ). Possible mechanistic pathways might involve N-1-/N-3 oxide tautomerism or Boulton–Katritzky rearrangement and the current study is the first attempt to compare these two reactions. The data collected agree with the first one and DFT calculations permitted also a significant correlation with 13C NMR experimental data and the assignment of the structure of each isomer. Finally, only one Meisenheimer intermediate for each electrophile/nucleophile combination was isolated by coupling the 2-aminothiazole derivatives with 4,6-dinitrobenzofuroxan (DNBF).

The S

9-Hydroxystearic acid (9-HSA) is an endogenous cellular lipid that possesses antiproliferative and selective effects against cancer cells. A series of derivatives were synthesized in order to investigate the effect of the substituent in position 9 and on the methyl ester functionality on the biological activity. The two separate enantiomers of methyl 9-hydroxystearate and of methyl 9-aminostearate showed antiproliferative activity against the HT29 cell line. This indicates the importance of position 9 groups being able to make hydrogen bonding with the molecular target. Further, this effect must be preserved when the carboxy group of 9-HSA is esterified. The biological tests showed that the amines, contrarily to methyl esters, resulted in cytotoxicity. A deep investigation on the effect of methyl (R)-9-hydroxystearate on HT29 cells showed an antiproliferative effect acting through the CDKN1A and MYCBP gene expression.

Nucleobases coordinated to Ruthenium centres have shown several promising properties for cancer treatments, demonstrating to have efficiency comparable to that of cis-Pt compounds, limiting toxic effects to intact cells and overcoming the drugs resistance after longer treatments. Thymine acetate (THAc) is proposed as a biomimetic model ligand to design potential Ruthenium-based antitumor drugs. Herein we report the reaction between Ru(H)2(CO)(PPh3)3, 1 and THAcH. The X-ray structure of the mono-,dihapto-thymine acetate species [(k1-O)(k2-O,O)Ru(THAc)2(CO)(PPh3)2] 2, unexpectedly exhibits cis-location for acetate ligands, likely ascribed to the prevalence of H-bonds and -stacking interactions. Conversely, DFT-calculations and NMR spectra suggest lower energy for the trans form where there are no contacts between the bulky phosphines. The DFT-calculated energies suggest the nature for NMR-intercepted plausible k1- or k2-intermediates. The carboxy-metal coordination is able to stabilize enol-tautomers through supramolecular H-interactions. The rotations of k1- and k2-acetate side arm of the THAc have also been exploited by correlating NMR signal patterns with the DFT energies. Figure 1: Torsional barrier of k1-(O) 3 and k2-(O,O) 4

The C-C coupling reaction between neutral aromatic carbon nucleophiles such as 1,3,5-triamino- and 1,3,5-trihydroxy-benzene derivatives and 7-chloro-4,6-dinitrobenzofuroxan (Cl-DNBF) or 7-chloro-4,6-dinitrobenzofurazan (Cl-DNBZ) gave in high yield the corresponding conjugated structures, which are of potential interest in the materials field. When chlorine is absent on the electrophile, as in 4,6-dinitrobenzofurazan (DNBZ), the reaction with 1,3,5-triaminobenzene derivatives produces Wheland-Meisenheimer (WM) zwitterionic intermediates, intercepted and fully characterized

The reaction between bis(2-benzothiazolyl)ketone and vinyl Grignard reagents bearing different substituents on the vinyl moiety gave the product derived from attack on the carbonylic carbon- and/or oxygen-atom. The regioselectivity of the attack depends on the kind of substituents bound to the vinylic carbon atoms and on their relative position. The reaction between vinylmagnesium bromide and 2-methyl-1-propenylmagnesium bromide was carried out under different experimental conditions and in the presence of radical scavengers. The results indicate a plausible mechanistic pathway involving radical intermediates in the case of O-alkylation, but a polar ones in the case of classic C-alkylation. This agrees with our previous reports indicating a key role played by the delocalization ability of the substituents bound to the carbonyl group in driving the regioselectivity of the vinylmagnesium bromide attack towards O-alkylation. Further support of this was obtained by diffractometric analysis of four distinct bis(heteroaryl)ketones.

none 4 Aromatic substitution reactions between 1,3-diaminobenzene and chloronitrobenzofurazan derivatives have never been reported so far. The aim of the current study was to synthesize novel electron-donor and -acceptor architectures of interest in applied fields and to provide new insights on the nucleophilic behavior of 1,3-diaminobenzenes. The reaction of 1,3-dipiperidinyl-, 1,3-dimorpholinyl-, 1,3-dipyrrolidinyl-, or 1,3-dimethylamino-benzene with 7-chloro-4,6-dinitrobenzofuroxan or with a series of chloro-nitrobenzofurazans has been carried out in mild conditions. The partners reactivity has been investigated by monitoring the reaction course through ¹H-NMR spectroscopy. The reaction occurred in a regioselective way, providing in good yields the novel C-C coupling compounds. Indications on the reactivity behavior for the studied nucleophiles have been relieved. open Micheletti, Gabriele; Bordoni, Silvia; Chugunova, Elena; Boga, Carla Micheletti, Gabriele; Bordoni, Silvia; Chugunova, Elena; Boga, Carla

The synthesis of a novel class of alcohol- and ether-functionalized indenyl ligands, focusing on the haptotropic rearrangements of the hybrid O-indenyl rhenium species, is herein described. η1- Indx OMeRe(CO)5 (12x) and η3-IndxOMeRe(CO)4 (13x, x=a, d) [IndaOMe=C9H6CH2CH(Me)OMe, 1a; Indd OMe=C9H6CH(CH2)3CHOMe, 1da] are examples of σ and allylic intermediates in the Cp substitution. The tuning of stereoelectronic effects of the functionalized alkyl chain or the coordinating solvent (MeCN, THF) allows the study of the relative stabilities of the intercepted solvento species η5-Indb OMeRe(CO)2(NCMe), 14b, η5-Indc OMeRe(CO)2(THF), 15c, or the chelate [η5:k1-OIndb, c ORe(CO)2], 16b,c {Indb OMe=[C9H6CH2CH(Ph)OMe]-, 4b; Indc OMe=[C9H6CH(Ph)CH2OMe]-, 4c}. DFT calculations reported on some of the IndO systems have been compared with those of smaller (CpO) 5a or larger (Flua O) 10a congeners, confirming the experimental findings. As peculiar examples of the underrepresented low-valent rhenium alkoxy species, the isolation of k1-O-HIndxORe(CO)5 [x=a, b] is also reported

This article illustrates current scholarly productions on European Romanticism and analyses the significance of a dialectical relation between literatures and cultures in the birth and development of European Romanticism. By analysing the works of August and Friedrich Schlegel, Germaine de Stael and Byron, the article aims to give a constructive overview of European Romanticism and of the British contribution to it.

The reaction of sodium cyanopentacarbonylmetalates Na[M(CO)5(CN)] (M=Cr; Mo; W) with cationic Fe(II) complexes [Cp(CO)(L)Fe(thf)][O3SCF3], [L=PPh3 (1a), CN-Benzyl (1b), CN-2,6-Me2C6H3 (1c); CN-But (1d), P(OMe)3 (1e), P(Me)2Ph (1f)] in acetonitrile solution, yielded the metathesis products [Cp(CO)(L)Fe(NCCH3)][NCM(CO)5] [M=W, L=PPh3 (2a), CN-Benzyl (2b), CN-2,6-Me2C6H3 (2c); CN-But (2d), P(OMe)3 (2e), P(Me)2Ph (2f); M=Cr, L=(PPh3) (3a), CN-2,6-Me2C6H3 (3c); M=Mo, L=(PPh3) (4a), CN-2,6-Me2C6H3 (4c)]. The ionic nature of such complexes was suggested by conductivity measurements and their main structural features were determined by X-ray diffraction studies. Well-resolved signals relative to the [M(CO)5(CN)] moieties could be distinguished only when 13C NMR experiments were performed at low temperature (from −30 to −50 °C), as in the case of [Cp(CO)(PPh3)Fe(NCCH3)][NCW(CO)5] (2a) and [Cp(CO)(Benzyl-NC)Fe(NCCH3)][NCW(CO)5] (2b). When the same reaction was carried out in dichloromethane solution, neutral cyanide-bridged dinuclear complexes [Cp(CO)(L)FeNCM(CO)5] [M=W, L=PPh3 (5a), CN-Benzyl (5b); M=Cr, L=(PPh3) (6a), CN-2,6-Me2C6H3 (6c), CO (6g); M=Mo, L=CN-2,6-Me2C6H3 (7c), CO (7g)] were obtained and characterized by infrared and NMR spectroscopy. In all cases, the room temperature 13C NMR measurements showed no broadening of cyano pentacarbonyl signals and, relative to tungsten complexes [Cp(CO)(PPh3)FeNCW(CO)5] (5a) and [Cp(CO)(CN-Benzyl)FeNCW(CO)5] (5b), the presence of 183W satellites of the 13CN resonances (JCW ∼ 95 Hz) at room temperature confirmed the formation of stable neutral species. The main 13C NMR spectroscopic properties of the latter compounds were compared to those of the linkage isomers [Cp(CO)(PPh3)FeCNW(CO)5] (8a) and [Cp(CO)(CN-Benzyl)FeCNW(CO)5] (8b). The characterization of the isomeric couples 5a–8a and 5b–8b was completed by the analyses of their main IR spectroscopic properties. The crystal structures determined for 2a, 5a, 8a and 8b allowed to investigate the geometrical and electronic differences between such complexes. Finally, the study was completed by extended Huckel calculations of the charge distribution among the relevant atoms for complexes 2a, 5a and 8a.

The reaction of the μ-aminocarbyne complex [Fe 2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCCMe 3 )(Cp) 2 ][SO 3 CF 3 ] ( 2 ) (Xyl=2,6-Me 2 C 6 H 3 ) with tolylacetylide, followed by treatment with HSO 3 CF 3 affords the complex [Fe 2 {μ-η 1 :η 3 C(Tol)CC(CMe 3 )N(H)CN(Me)(Xyl)}(μ-CO)(CO)(Cp 2 )][SO 3 CF 3 ] ( 3 ) (Tol=4-MeC 6 H 4 ). The X-ray molecular structure of 3 reveals the peculiar character of the bridging ligand, which exhibits both η 1 :η 2 allene and aminocarbene nature. The formation of 3 proceeds through several intermediate species, which have been detected by IR spectroscopy. Addition of HSO 3 CF 3 at an early stage of the reaction between 2 and LiCCTol leads to the formation of the imine complex [Fe 2 {μ-CN(Me)Xyl}(μ-CO)(CO){NHC(CCTol)CMe 3 }(Cp) 2 ][SO 3 CF 3 ] ( 6 ) indicating that the first step of the reaction consists in the acetylide addition at the coordinated NCCMe 3 . The molecular structure of 6 has been elucidated by an X-ray diffraction study.

Reaction of [Fe2(μ-CS)(μ-CSMe)Cp2(CO)2]+ (1) with sodium N,N-dimethyldithiocarbamate [Me2dtc]Na affords a mixture of the dithiocarbene [Fe Fe(μ-CS){μ-C(SMe)S C(S)NMe2}Cp(CO)] (2) and the thiocarbyne [Fe2(μ-CS)(μ-CSMe)(μ-S2CNMe2)Cp2] (3). Complex 2 is quantitatively converted into 3 by photochemical irradiation. The X-ray molecular structure of 3 demonstrates the presence of three bridging ligands and exhibits the shortest FeFe interaction found in similar systems [2.453(1) A]. Complex 3 can also be obtained by reacting [Me2dtc]− with the di-solvento thiocarbyne [Fe2(μ-CS)(μ-CSMe)(NCMe)2Cp2]+ (1a). By contrast no stable addition product has been isolated in analogous reactions involving the thiocarbyne [Fe2(μ-CO)(μ-CSMe)Cp2(CO)2]+ (1b). The [Me2dtc]− nucleophilic addition at the μ-C to form [Fe2(μ-CO){μ-C(CN)SC(S)NMe2}Cp2(CO)2] (4a) is obtained starting from [Fe2(μ-CO){μ-C(CN)(SMe2)}Cp2(CO)2]SO3CF3 (1d). Photochemical reaction of the cyanocarbene 4a causes intramolecular ring closure affording [Fe Fe(μ-CO){μ-C(CN)S C(S)NMe2}Cp2(CO)] (5a).

The synthesis of new Fe(II) 5-aryl tetrazolate complexes [CpFe(CO)(L)(N4C−C6H4−CN)] (4) [L = CO (4a); PPh3 (4b); P(OCH3)3 (4c); CN-2,6-Me2C6H3 (4d)] is described. The target compounds were obtained by addition of sodium azide to the parent 1,4-dicyanobenzene complexes [CpFe(CO)(L)(NC−C6H4−CN)][O3SCF3] (2a−d). X-ray molecular structure of 4c confirms the predictions based on NMR (1H, 13C) studies concerning the coplanarity between the tetrazole and phenyl rings, with consequent interannular conjugation effect. The multidentate nature of the tetrazole ring involves the presence of different sites that can undergo electrophilic attack; reaction of complexes 4a−c with methyl triflate afforded the methylated cationic complexes [CpFe(CO)(L)(CH3−N4C−C6H4−CN)][O3SCF3], 5a−c, whose 1H and 13C NMR spectroscopy data suggested out-of-plane rotation of the phenyl ring and subsequent large reduction of interannular conjugation. Noteworthy, the same effect was obtained in a reversible way by addition of triflic acid to ...

The reactions of [Fe 2 {μ-C(X)SMe 2 }(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=CN 2a , H 2b ; Cp=η-C 5 H 5 ) with Li 2 Cu(CN)R 2 (R=Me, Bu n , Ph, CCC 6 H 4 Me-4, C 4 H 3 S) give the neutral μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 3 ) arising from nucleophilic attack at the bridging carbon and SMe 2 displacement. Likewise, 2a , b react with the sodium salt of dimethylmalonate, diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane and benzylcyanide, resulting in the formation of the corresponding functionalized μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 5 – 7 ) (X=CN, H; R=CH(COOMe) 2 , CH(COOEt) 2 , CH(COOMe)(COMe), CH(COMe) 2 , CH(COPh) 2 , CH(Ph)CN). The dichetone adducts [Fe 2 {μ-C(X)CH(COR) 2 }(μ-CO)(CO) 2 (Cp) 2 ] (X=CN, H; R=Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the complexes [Fe 2 {μ-C(X)CH 2 C(O)R}(μ-CO)(CO) 2 (Cp) 2 ]. Reactions of 2a , b with LiBu or PhLi result in the formation the metallacycles [Fe 2 {μ-C(X)S(Me) CH 2 }(μ-CO)(C O)(CO)(Cp) 2 ] (X=CN, 4a ; H 4b ) which arise from the deprotonation of an SMe group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a , b with that of the μ-carbyne diiron complexes [Fe 2 (μ-CX)(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=H, SMe, NMe 2 ) is presented.

The heteropolynuclear cyano-bridged complexes [(C5H5)Fe(CO)(CNMLn)(CNM′L′n)], {MLn = M′L′n = (C5H5)Fe(CO)2 or W(CO)5, MLn = (C5H5)Fe(CO)2, M′L′n = W(CO)5} and mixed isocyanide complexes [(C5H5)Fe(CO)(CNMLn)(CNR)], {MLn = W(CO)5, R = CPh3; MLn = (C5H5)Fe(CO)2, R = CH3} have been obtained by metallation or alkylation of the two terminal CN ligands of K[(C5H5)Fe(CO)(CN)2]. Comparison of the bonding properties of the CNMLn and CNR ligands, based upon their relevant spectroscopic data, are discussed. Furthermore, two new isomeric heterobinuclear cyano-bridged complexes of the form [(C5H5)(CO)2FeCNW(CO)5] and [(C5H5)(CO)2FeNCW(CO)5] have been synthesized and fully characterized by spectroscopic techniques. Finally the reactions with nucleophiles of the last two compounds have been also examined.

(1 S ,5 S )-(−)- and (1 R ,5 R )-(+)- β -pinene have been hydroformylated in toluene to give (1 S ,2 R ,5 S )- and (1 R ,2 S ,5 R )-10-formylpinane with up to 95% diastereoselectivity using bimetallic CoRh(CO) 7 as a catalyst; the latter was generated in situ from preformed Co 2 Rh 2 (CO) 12 or a stoichiometric mixture of either [Rh 4 (CO) 12 ] or [Rh 6 (CO) 16 ] and [Co 2 (CO) 8 ]. At 70–125°C and under 60 atm of syngas, the yields of hydroformylated products do not exceed 30% because of the concomitant isomerization of β- to α-pinene. In all cases the catalyst is recovered as a mixture of soluble cobalt carbonyl derivatives and a crystalline precipitate that contains most of the rhodium, mainly as [Rh 6 (CO) 16 ]. Comparable yields and diastereoselectivities were obtained from reactions in tetrahydrofuran with a mixture of [Rh 4 (CO) 12 ] and [N(PPh 3 ) 2 ]Cl as the catalyst precursor. The corresponding (1 S ,2 S ,5 S )- and (1 R ,2 R ,5 R )-10-formylpinanes, along with the corresponding alcohols, were obtained diastereoselectively by the use of bimetallic CoRh or homometallic Rh carbonyl catalysts modified with bis(diphenylphosphine)ethane (dppe). When unidentate phosphines such as triphenylphosphine were used in place of dppe, as the ligand/metal (L/M) ratio was raised the diastereoselectivity of both the hetero- and the homo-metallic catalytic system fell progressively, and was completely lost for L/M ≥ 4. However, a further increase in L/M to ca. 70–100 allows chemio- and diastereo-selective synthesis of both the (1 S ,2 S ,5 S )- and (1 R ,2 R ,5 R )-10-formylpinane. The (1 S ,2 R ,5 S )-, (1 S ,2 S ,5 S )-, (1 R ,2 R ,5 R )- and (1 R ,2 S ,5 R )-10-formylpinane diastereomers were isolated by distillation under reduced pressure and fully characterized by IR, UV, 1 H and 13 C NMR and circular dicroism (CD) spectroscopy, and mass spectrometry. The possible factors favouring the diastereoselective hydroformylation of β-pinenes under the conditions used are discussed.

The bis(µ-thiocarbene)[(cp)(OC)Fe{µC(CN)SMe}{µ-C([graphic omitted]e(cp)](X = H or CN; cp =µ-C5H5) and all the intermediate species obtained from the thiocarbyne derivative cis-[Fe2(µ-CS){µ-C(SMe)}(CO)2(cp)2]-[SO3CF3]viaµ-C stereoselective addition of X–, photochemical formation of [(cp)[graphic omitted]Me)X}(µ-CS)Fe-(CO)(cp)] followed by stepwise addition of MeSO3CF3 and (NBu4n)CN at the bridging CS group have been prepared and characterized. Attempts to obtain the bis(µ-thiocarbene)[{Fe[µ-C(CN)SMe](CO)(cp)}2] failed. The crystal structure of [{[graphic omitted]Me](cp)}2] which demonstrates the presence of two doubly bridging thiocarbene groups has been determined. The results show that bis(µ-thiocarbene) derivatives are stable when at least one of the ligands acta as a double bridge via a S–Fe bond.

Electrochemistry of the μ-cyanoalkylidene complexes [Fe 2 (CO) 2 (cp) 2 ( μ -CO){ μ -C(CN)(X)}] n + ( n = 0, X = CN, H, Me, SMe, OMe, OEt, OPh, OCH 2 CH=CH 2 , PEt 2 , piperidinyl; n = 1, X = PMe 2 Ph) in nonaqueous solutions shows a one-electron reduction to the corresponding paramagnetic monoanions, which have been characterized by EPR spectroscopy. The presence of the positive charge in [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(CN)(PMe 2 Ph)}] + makes the one-electron addition significantly easier than to the neutral complexes. None of the 19-electron anions are fully stable and all undergo slow decomposition reactions, the rates of which are a function of the X substituent. Access to the radical anion intermediates [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(CN)(X)}] − does not trigger Electron Tra Chain catalytic substitution reactions of CO by phosphines, but allows these reactions to be successfully carried out by different methods, such as chemical reduction, CO photolysis and use of Me 3 NO. The CO-substituted derivatives [Fe 2 (cp) 2 (CO)(PMe 2 Ph)(μ-CO){μC(CN)(X) (X = CN, H, SMe) and [Fe 2 (cp) 2 ( μ -CO)( μ -dppm){ μ -C(CN)(X)}], (X = H, CN; dppm = Ph 2 PCH 2 PPh 2 ) were obtained. The one-electron reduction of the monophosphine-substituted complexes is fully irreversible and occurs at potentials 0.3–0.4 V more negative than those of the corresponding precursors. The different methods for promoting CO displacement in the μ-alkylidene complexes have been compared; the photolytic method affords the highest yields.

The reaction of [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(H)(SMe)}] (cp=η-C 5 H 5 ) with MeSO 3 CF 3 forms the sulfonium-methylidene complex [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(H)(SMe 2 )}]SO 3 CF 3 ( 3 ). Compared to Casey's methylidyne complex [Fe 2 (CO) 2 (cp) 2 (μ- CO)(μ-CH)]PF 6 ( 1 ), compound 3 appears to be more stable and easier to handle, still maintaining a reactivity centered at the μ-carbon. In fact 3 undergoes replacement of SMe 2 by a variety of nucleophiles X, at room temperature, affording the corresponding cationic [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(H)(X)}]SO 3 CF 3 (XNMe 3 , PMe 3 , PPh 3 , PHPh 2 ) or neutral [Fe 2 (CO) 2 (cp) 2 (μ- CO){μ-C(H)(X)}] (XH − , MeO − , CN − ) μ-methylidene derivatives, in good yield. The phosphonium complex [Fe 2 (CO) 2 (cp) 2 (μ- CO){μ-C(H)(PHPh 2 )}]SO 3 CF 3 has been deprotonated with NEt 3 to yield the novel phosphino-methylidene complex [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(H)(PPh 2 )}]. The presence of the SMe 2 moiety in 3 reduces, compared to 1 , the electrophilic character of the μ-C carbon, as evidenced by the reaction with styrene.

The complex [Fe 2 (CO) 2 (Cp) 2 (μ-CS)(μ-CSMe)]SO 3 CF 3 ( 1 ) reacts with N n Bu 4 NCO to give [Fe 2 (CO) 2 (Cp) 2 (μ-CS){μ-CNC(O)SMe}] ( 2 ). This reaction has been carried out separately for both the cis and trans isomers of 1 . Complex cis - 2 undergoes S -methylation with MeOSO 2 CF 3 affording the novel thiocarbyne derivative [Fe 2 (CO) 2 (Cp) 2 (μ-CSMe) {μ-CNC(O)SMe}]SO 3 CF 3 ( 3 ), into which in turn an additional NCO − anion inserts to yield the bis(μ-acylisocyanide) complex [Fe 2 (CO) 2 (Cp) 2 {μ-CNC(O)SMe} 2 ] ( 4 ). All the reactions described are stereospecific and the derivatives 2–4 do not exhibit cis-trans isomerization.

A large number of iron and ruthenium dinuclear complexes containing heteroatom substituted carbene ligands have been obtained by two different synthetic routes. The first method consists in reacting heteroatom substituted μ-carbyne cationic complexes with CN− ion. The second involves the displacement of the SMe2 molecule in the sulfonium [Fe2{μ-C(CN)(SMe2)}(μ-CO)(CO)2CP2]SO3CF3 by appropriate nucleophilesX− (X=OR, SR, NR2, PR2). Spectroscopic (IR, NMR) and structural investigations together with reactivity studies on these complexes have greatly contributed to better understanding the factors which favor bridging vs. terminal coordination of heteroatom substituted carbene ligands.

A large number of iron and ruthenium dinuclear complexes containing heteroatom substituted carbene ligands have been obtained by two different synthetic routes. The first method consists in reacting heteroatom substituted μ-carbyne cationic complexes with CN− ion. The second involves the displacement of the SMe2 molecule in the sulfonium [Fe2{μ-C(CN)(SMe2)}(μ-CO)(CO)2CP2]SO3CF3 by appropriate nucleophilesX− (X=OR, SR, NR2, PR2). Spectroscopic (IR, NMR) and structural investigations together with reactivity studies on these complexes have greatly contributed to better understanding the factors which favor bridging vs. terminal coordination of heteroatom substituted carbene ligands.

The dinuclear complexes [Fe2(η5-C5H5)2(µ-CO)(CO)2{µ-CH(CN)}]1 and [Fe2(η5-C5H5)2(µ-CO)(CO)2{µ-C(CN)2}]2 have been obtained from the sulfonium cation [Fe2(η5-C5H5)2(µ-CO)(CO)2{µ-C(SMe2)(CN)}]+via SMe2 displacement with H– and CN–, respectively. Complex 1 is present in solution and in the solid state as a mixture of isomers, the relative composition depending on the solvent. The structures of the cis isomers of 1(cis-1a) and 2(cis-2) have been determined by single-crystal X-ray diffraction: cis-1a, monoclinic, space group P21/m, a= 6.408(1), b= 13.58(1), c= 8.004(1)A, β= 93.17(2)°, Z= 2, 2225 measured, 1392 unique observed reflections [I > 2.0σ(I)], R= 0.035, R′= 0.036; cis-2, orthorhombic, space group Pnma, a= 10.346(3), b= 12.313(4), c= 12.590(3)A, Z= 4, 1645 measured, 1115 unique observed reflections [I > 2.0σ(I)], R= 0.027, R′= 0.029. The dynamic behaviour of the two complexes in the solid state has been investigated by variable-temperature 1H spin–lattice relaxation time measurements and 13C magic angle spinning NMR spectroscopy. The activation energies for the reorientational processes have been estimated. The separate intra- and intermolecular contributions to the total reorientational barriers have been evaluated by means of potential-energy barrier calculations within the pairwise atom–atom approach.

The cyclopentadienide nucleophilic ring opening on the cyclopentene oxide affords diastereoselectively an efficient entry to a new polyalcoholic (1,2,4)-C5H2[CH(CH2)3CHOH]3 propeller-like, hybrid ligand CpOOO. The diastereoselective rhodium complexation gives rise almost quantitatively to a new class of racemic CpOOORh(L,L) (L,L ) nbd, cod, C2H4, CO) complexes. Thermal treatment gives predominantly the air-stable CpOOORh(nbd) rac-4a (73.5%), having SP planar chirality, as determined by X-ray diffraction studies. It has also been possible to isolate its stable atropisomer rac-4c (20.5%), while the minor kinetic isomer rac-4b, showing opposite planar chirality (∼10%), has been identified by NOESY NMR experiments. The high solubility in water and benzene, evidencing the amphiphilic character, has been measured by the n-octanol/water partition coefficient. The intermolecular H-binding, due to the hydroxy groups, plays a crucial role in selecting the rhodium coordination in the reaction mixture, whereas in the solid, it determines the supramolecular organization. DFT calculations in vacuo are in agreement with the spectroscopically identified structures.

The reactions of the metallacyclic complex [Cp(CO)FeC(S)SC(Fp)S] (1) (Cp = η-C5H5) with Group IB and IIB metal compounds have been investigated. Electrophilic addition at the thione sulphur atom has been observed in all cases. The reactions of 1 with the coinage metal complexes [MX(PPh3)]n (M = Cu, X = I, n = 4; M = Ag, X = Cl, n = 4; M = Au, X = Cl, n = 1) in the presence of TlPF6 give the adducts [Cp(CO)FeC{SM(PPh3)}SC(Fp)S]PF6 (2), which have been characterizded spectroscopically. The mercury salt [HgMe]PF6 reacts similarly with 1 to afford [Cp(CO)FeC(SHgMe)SC(Fp)S]PF6 (3), whereas mercury dihalides give products that have been shown by an X-ray diffraction study in the case in which X = Br to be halogen-bridged dimers of the type [Cp(CO)FeC(SHgX2)SC(Fp)S]2. The bromine-bridged dimer displays Ci symmetry. The coordination around the Hg atoms involves four normal and one weak bonds, and the geometry can be described as a distorted trigonal bipyramid. Zinc chloride reacts with 1 to give an air-sensitive unstable derivative that is tentatively formulated as [Cp(CO)FeC(SZnCl2)SC(Fp)S].

Easily accessible cationic compounds with heteroatoms substituted alkylidyne ligands bridging metal-metal bond provide an opportunity to study the reactions of the μ-CX (X= SR,NR2) groups with C, N, P, S, nucleophiles. Reactivity patterns are strongly influenced by the nature of both the nucleophile and the alkylidyne ligand. Discussion will focus on the reaction in which the alkylidyne fragment is transformed into a Fischer type carbene ligand bridging the metal-metal bond. Spectroscopic (IR, NMR) and structural investigations together with reactivity studies on these complexes have greatly contributed to better understanding the factors which favour bridging vs. terminal coordination of heteroatom substituted carbene ligands.

The action of MeSO3CF3 on [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)SMe}]1(cp =η5-C5H5) yields [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)SMe2}][SO3CF3]2. The sulphonium cation is also obtained, trapped in the unusual triflate complex Fe(OSO2CF3)4{Fe2(cp)2(CO)2(µ-CO)[µ-C(CN)SMe2}2]3, by treating the thiolcarbamate [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)N(Me)C(O)SMe}]4 with MeSO3CF3. The X-ray crystal structure of 3 shows the iron(II) centre co-ordinated by four O-bonded triflate anions and by two, mutually trans-disposed, N-co-ordinated organometallic cations in an octahedral geometry.

Reaction of FpC(S)SMLn (Fp = Fe(η-C5H5)(CO)2; MLn = Fp (1a), Re(CO)5 (1b)) with MeC(O)Cl affords [FpCS]Cl and LnMSC(O)Me (3);1a reacts with (CF3CO)2O to yield [Fp(CO)]CF3CO2 and FpSC(O)CF3 (5). In both cases the reactions have been shown to occur via the unstable S-acylated intermediates [FpC[SC(O)R]SMLn]+ (R = CF3, Me). Alkylation of 1a with RBr (R = Me, Et, CH2Ph, CH2CHCH2) or CF3SO2OR (R = Me, Et) followed by treatment of the stable S-alkylated derivatives [FpC(SR)SFp]+ with I− provides a useful alternative method for the synthesis of a variety of FpC(S)SR.

The dimeric rhodium(0) complex [(CH3C(CH2PPh2)3)2Rh2(μ-CO)2] (1), undergoes oxidative-addition reactions with H2 and H+, with metalmetal bond breaking, to form a monomeric and a dinuclear hydride derivative, respectively. The oxidation of 1 by electrochemistry or chemical agents affords the paramagnetic cation [(CH3C(CH2PPh2)3)2Rh2(μ-CO)2]+. The structure of this latter, which has been determined by X-ray diffraction, closely resembles that of the uncharged species 1, but with a shorter RhRh bond distance.

Multielement n.m.r. measurements (1H, 1H-{103Rh}, 13C, 13C-{103Rh}, and 103Rh) show that protonation of [Rh6(CO)13C]2– at low temperature gives [Rh6H(CO)13C]– which contains an edge-bridging hydride with the carbonyl distribution being very similar to that found in [Rh6(CO)13C]2– Warming this solution to < –20 °C results in complete CO- and H-migration over the Rh6 octahedron and at –20 °C there is formation of [Rh6H(CO)15C]– together with loss of hydrogen to give [Rh12(CO)24(C)2]2– which has been spectroscopically characterised. Multielement n.m.r. studies on products resulting from the reaction of [Rh6(CO)13C]2–(1 mol equiv.) with diphosphines Ph2P(CH2)nPPh2[0.5 mol equiv.; n= 1,2 (dppe), 3, or 4] or Ph2AsCH2CH2AsPh2 suggest that they all have similar structures and an X-ray crystallographic analysis of the dppe derivative shows it to be [Rh6(CO)11C(µ-dppe)]2–.

Reaction of the bridging-cyanocarbene complex Cp2Fe2(CO)2 (μ-CO) [μ-C(CN)N(Me)COSMe], 1, with MeSO3CF3 results in the removal of MeNCO to produce the cationic carbene Cp2Fe2(CO)2(μ-CO) [μ-C(CN) (SMe2)]+ , 2 probably via migration of SMe2 to the μ-carbon atom. The sulfonium complex 2 is also obtained by reacting the cyano(thiolkoxy)-methylene derivative Cp2Fe2(CO)2(μ-CO) [μ-C(CN)SMe], 3, with MeSO3CF3. The cyanocarbyne-like carbon in 2 is attacked by heteroatom and carbon nucleophiles giving a general entry to the synthesis of the neutral Cp2Fe2(CO)2(μ-CO) [μ-C(CN)X] derivatives (X = SCH3, NMe2, OR, H, CN and Me). The spectroscopic properties of these complexes together with the X-ray structural investigation of the Cp2Fe2(CO)2(μ-CO) [μ-C(CN)2] are reported.