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Highly soluble ligand stabilized tin oxide nanocrystals have been prepared by the postsynthetic modification of hydrous tin oxide with the simple short-chain carboxylic acids, acetic acid and trifluoroacetic acid. The surface modified nanoparticles are soluble in common organic solvents at concentrations of up to 2 g/mL and may be stored indefinitely in the solid-state with no loss of solubility. The nature and role of the surface carboxylate groups has been assessed through a combination of thermogravimetric analysis and infrared spectroscopy. The effect of surface modification on the sintering behavior of the nanomaterials has also been investigated. Tuning the surface chemistry of the hybrid nanocrystals allows the generation of monolithic gels, while their high solubility permits the preparation of high quality thin films using simple solution processing techniques.

The reactions of 1-substituted-imidazolium-3-dicyanomethanides with maleic anhydride gave new ylide products from a Michael reaction and 1,2-rearrangements. These experiments, combined with theoretical calculations, provide an interesting new perspective on the Boekelheide–Fedoruk ring expansions.

The focus of this investigation was on adduct formation, and its consequences, between organotin(IV) Lewis acids and the tetradentate salicylaldimine ligands H23-MeOsalen [N,N‘-bis(3-methoxysalicyl...

The crystal structures of o-toluidinium chloride (1), o-toluidinium bromide (2) and two polymorphs of bicifadine hydrochloride (3) have been determined. The polymorphs of 3 differ in their molecular conformation and in their mode of packing. Crystallisation studies and quantum mechanical calculations show that the more readily crystallisable polymorph grows from the thermodynamically most stable conformer. On heating, conversion to the second polymorph takes place just below the melting point. The crystal structures of 1, 2 and the first polymorph of 3 have been successfully predicted using a procedure that is suitable for simple ionic organics.

The 2,6-spirodicyclohexyl substituted nitroxide, cyclohexane-1-spiro-2′-(3′,5′-dioxo-4′-benzylpiperazine-1′-oxyl)-6′-spiro-1″-cyclohexane (BODAZ), was investigated as a mediator for controlled/living free-radical polymerization of styrene. The values of the number-average molecular weight increased linearly with conversion, but the polydispersities were higher than for the corresponding 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) and 2,5-bis(spirocyclohexyl)-3-benzylimidazolidin-4-one-1-oxyl (NO88Bn) mediated systems at approximately 2.2 and 1.6 at 100 and 120 °C, respectively. These results were reflected in the rate coefficients obtained by electron spin resonance spectroscopy; at 120 °C, the values of the rate coefficients for polystyrene-BODAZ alkoxyamine dissociation (kd), combination of BODAZ and propagating radicals (kc), and the equilibrium constant (K) were 1.60 × 10−5 s−1, 5.19 × 106 M−1 s−1, and 3.08 × 10−12 M, respectively. The value of kd was approximately one and two orders of magnitude lower, and that of K was approximately 20 and 7 times lower than for the NO88Bn and TEMPO adducts. These results are explained in terms of X-ray crystal structures of BODAZ and NO88Bn; the six-membered ring of BODAZ deviates significantly from planarity as compared to the planar five-membered ring of NO88Bn and possesses a benzyl substituent oriented away from the nitroxyl group leading to a seemingly more exposed oxyl group, which resulted in a higher kc and a lower kd than NO88Bn. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3892–3900, 2003

1,3-Dipolar cycloaddition of [1,4]benzoxazepine N-oxides to triple and double bonded dipolarophiles affords di- and tetrahydro-isoxazolobenzoxazepines in the first reported synthesis of this tricyclic ring system. It is observed that in addition to the acetylenic dipolarophiles the diastereofacial selectivity varied both with the nature of the C-nitrone substituent as well as on the degree of substitution of the dipolarophile. Addition to alkene substrates occurred regiospecifically furnishing “5-substituted” isoxazolidine rings. For each olefinic dipolarophile the major cycloadduct arose via an endo-addition of the dipolarophile to the β-face of the dipole. Some of the new tricycles displayed sharp signals in their pmr spectra whilst signal duplication/broadening was evident for others indicating the adducts exist in solution as pairs of conformational isomers which reach coalescence at or close to room temperature. Preliminary investigations show the isoxazolidine ring of the tricycles can be cleaved under reductive and oxidative conditions affording novel benzoxazepines. The structure of the cycloadduct 6a formed between the C-phenyl nitrone 5a and dimethyl acetylenedicarboxylate and has been solved by single crystal xray analysis.

The reaction of (−)-camphorquinone with excess moist bromine gives (−)-(1S,5S)-1-bromomethyl-3,3-dibromo-8,8-dimethyl-7-oxabicyclo[3.2.1]octane-2,6-dione rather than 1-bromomethyl-3,5-dibromo-8,8-dimethyl-7-oxabicyclo[3.2.1]octane-2,6-dione as has been reported in the literature. The controlled reaction of moist bromine with (−)-camphorquinone leads to (−)-(1S,5S)-3,3-dibromo-1,8,8-trimethyl-7-oxabicyclo[3.2.1]octane-2,6-dione and not to 5-bromo-1-bromomethyl-8,8-dimethyl-7-oxabicyclo[3.2.1]octane-2,6-dione.

Preparation of a series of terminally and internally substituted delta-alkenyl and delta-alkynyl esters 6,7 and 9, potential precursors to oxazin-2-one nitrones, has been attempted. Condensation between pyruvic or benzoylformic acid and the appropriate alcohol proceeded smoothly in some cases whilst allylic transposition was a major feature in other cases most especially during reactions with alpha-vinylbenzyl alcohol. Oximation of piyruvic acid derivatives furnished E-oxime isomers whilst benzoylformic acid derivatives afforded mixed geometrical isomers. The E-oxime of 4a(1) carrying an internal Me group undergoes facile thermal cyclisation affording nitrones 1c and 1d in good yield. Oximes E-5a,b with a terminal methyl substituent on the alkene moiety furnish nitrone only under the influence of an external electrophile [PhSeBr/AgBF4]. A terminal Ph substituent on 5c,d prohibits formation of the cyclic dipole irrespective of reaction conditions, and whilst 5d reacts to afford a bicyclic isoxazolofuranone 13 by an IOOC reaction (intramolecular oxime olefin cyclisation) 5c remains thermally inert. Finally delta-alkynyl oximes 9c,d also failed to cyclise. The regio- and stereochemical characteristics of the cycloadditions between the new dipoles and electron poor olefinic dipolarophiles have been investigated. The conditions needed for reaction were rather forcing since the dipoles are somewhat stabilised by the adjacent alkoxycarbonyl group. All reactions proceeded regiospecifically to give adducts with 5-substituted isoxazolidine rings whilst diastereoselectivity varied with the choice of dipolarophile and the steric demands of the nitrone substituents. The phenylselenyl dipole 10a could not be trapped by any dipolarophiles bar dimethyl acetylenedicarboxylate.

A molecular mechanics force field has been developed for the conformational analysis of amido- and α-aminoferrocenes. Parameterization for ring-substituent rotational barriers in amidoferrocenes and other cross-conjugated derivatives have been calculated using DFT on both the free and complexed cyclopentadienyl ligand. Modeled structures of (diisopropylamido)- and (dimethylamido)ferrocene and N,N-dimethyl-α-ferrocenylethylamine are in agreement with those determined through single-crystal X-ray diffraction. The diastereoselective lithiation of N,N-dimethylferrocenylethylamine and sparteine-mediated enantioselective lithiation of (diisopropylamido)ferrocene using MeLi have been modeled through an assumed reversible adduct formation at the amine nitrogen or amide oxygen, followed by an irreversible ring lithiation. Results indicate that selectivity results from ring lithiation via the adduct conformer with the shortest C−Hring- - -H3C−Li interaction.

The potent electron-donating group [(CpFeCO)2(µ-CO)(µ-C=CH−)] was combined with different tropylium-based acceptors yielding the push-pull complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=A)][BF4] where =A represents [=CH−(η7-C7H6)Cr(CO)3]+ (5), [={C10H7}]+ (azulenylium) (7) [={C10H4Me2iPr}]+ (guaiazulenylium) (8). Crystal structures of the precursor complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=CH−C7H7)] (3), [(CpFeCO)2(µ-CO){µ-C=CH−CH=CH−(η6-C7H7)Cr(CO)3}] (4) and the push-pull derivative 5 are presented. Whereas complexes 3 and 4 demonstrate localised carbon−carbon double and single bonds in the π-bridge between the diiron moiety and the seven-membered ring a small but distinct π-bond delocalisation can be observed in the π-linker of the cationic derivative 5. From the NMR spectroscopic results a correlation between the 13C NMR shift of the bridging carbon atom µ-C of the diiron unit and the coupling constant J(1H-1H) of the β- and γ-protons of the π-bridge was found. This correlation indicates an increased π-bond delocalisation throughout the conjugated bridge with respect to the electron-accepting capability in the order tricarbonyl(η7-cycloheptatrienylium)chromium < guaiazulenylium < azulenylium implying a predominantly charge-delocalised form in the case of the azulenylium complex 7. Considerably large first hyperpolarisabilities β were determined for 5 and 8 by means of hyper-Rayleigh scattering. Based on the two-level model β0 values were calculated and related to the bond-length alternation in the π-linker. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Reactions of organosilicon, -germanium, -tin, -lead, -antimony, and -tin tetrahalide Lewis acids with VO(salen) [H(2)salen = N,N'-bis(salicylidene)ethane-1,2-diamine], related vanadyl salicylaldimines, VO(acacen) [H(2)acacen = N,N'-bis(acetylacetonato)ethane-1,2-diamine], and VO(acac)(2) (acac = acetylacetonato) have been investigated, revealing VO(salen) and VO(acacen) to be significantly stronger vanadyl donors than VO(acac)(2). The vanadyl donor strength of VO(salen) significantly diminishes with the introduction of electron-withdrawing substituents on the salicylaldimine ligand, and the introduction of methyl substituents on the imine carbon atoms can result in a preference for phenolic over vanadyl oxygen donation. Vanadyl donation results in an increase in the vanadyl bond length, while it leaves the distance of vanadium from the basal plane relatively unaffected. Coordination of water trans to a vanadyl oxygen that is involved in a donor bond to tin or lead has little or no effect on the vanadyl bond length but results in a marked movement of vanadium toward the basal plane and a decrease of the V=O-D (D = Sn or Pb) bond angle by as much as 13 degrees, the latter reflecting a loss of multiple bond character of the vanadyl bond. Formation of a vanadyl donor bond results in a decrease in both the vanadyl stretching frequency (infrared spectrum) and energy of the e(pi)-- b(2) transition (electronic spectrum), the latter being intimately related to the strength of the vanadyl donor bond, while the shift of the b(1)-- b(2) transition to higher or lower energy is relatively small for vanadyl salicylaldimine and beta-ketimine complexes. Donation through the phenolic oxygen atoms results in an increase in the vanadyl stretching frequency and energy of the e(pi)-- b(2) transition, which can result in e(pi)-- b(2)/b(1)-- b(2) energy crossover.

The iron hydrido complex HFe(CO)2{P(OPh)3}{(PhO)2POC6H4} (1), was rapidly deprotonated by DBU or [BzMe3N][OH] in THF to afford the new carbonyl iron anion [Fe(CO)2{P(OPh)3}{(PhO)2POC6H4}]− ([2]−), containing an ortho-metallated triphenyl phosphite ligand. Complex [2]− reacted with triorganostannyl and plumbyl salts and with halogens to give the octahedral FeII compounds Fe(CO)2{P(OPh)3}{(PhO)2POC6H4}(X) (X=SnPh3, 3; SnMe3, 4; PbPh3, 5; PbMe3, 6; Cl, 7; Br, 8; I, 9). The Group 14 complexes 3–6 were obtained in one isomeric form in which the PIII-donor atoms are mutually cis, the carbonyl ligands are cis and the P(OPh)3 and MR3 (M=Sn, Pb; R=Ph, Me) groups are trans as determined by solution-state IR, 31P and 13C NMR spectroscopic data. This geometry was confirmed for 3 by a single crystal X-ray diffraction study. The halide complexes, however, were obtained as a mixture of isomers. The major isomer (7, X=Cl; 8a, X=Br; 9a, X=I) has cis P atoms, trans CO groups and the halide located trans to the phosphorus atom of the ortho-metallated phosphite ligand. The structure of 9a was confirmed by an X-ray diffraction study. Two other isomers, designated 8b (X=Br) and 9b (X=I), with cis P atoms and cis CO groups were isolated from the reactions of [2]− with Br2 and I2, respectively. The structure of the latter was established by X-ray crystallography and is related to 9a by exchange of the P(OPh)3 ligand and a carbonyl group such that the metal-bound C atom of the five-membered metallacycle is trans to CO. The stereo-geometry of 8b could not be unambiguously assigned from the spectroscopic data; however, two of the seven possible geometric isomers were suggested as plausible structures.

Reaction of menthylmagnesium chloride with pyridine-2-carbaldehyde gives a mixture of four isomeric chiral menthyl- and neomenthyl-substituted pyridylcarbinols which were fully characterised by a combination of spectroscopic and X-ray crystallographic methods. All of these alcohols catalyse the addition of diethylzinc to benzaldehyde, but with disappointing enantioselectivities.

In the reactions of phthalazinium dicyanomethanide 1,3-dipole with electron-poor monosubstituted alkene and alkyne dipolarophiles the dicyanomethanide terminus bonds to the unsubstituted carbon giving 1-substituted pyrrolo[2,1-a]phthalazines. With electron-rich dipolarophiles the regiochemistry is reversed and the products are 2-substituted pyrrolo[2,1-a]phthalazines. An unexpected reversal of regiochemistry occurred with methyl methacrylate, due to a steric effect of the C–Me group, and the main product was 2-exo-methyl-2-endo-methoxycarbonyl-3,3-dicyano-1,2,3,10b-tetrahydropyrrolo[2,1-a]phthalazine, 17. endo Cycloadditions were strongly favoured with alkene dipolarophiles containing π bonds in substituents on the alkene unit. With N-substituted maleimides endo products were formed exclusively even when the N-substituent was tBu or adamantyl. Only with alkoxyvinyl ethers were exo-cycloadducts encountered. The mechanisms are discussed in conjunction with DFT calculations. An X-ray crystal structure is reported on endo-N-tert-butyl-3,3-dicyano-1,2,3,10b-tetrahydropyrrolo[2,1-a]phthalazine-1,2-dicarboximide, 25.

1:1 and 1:2 adducts of diphenyltin dichloride with triphenylphosphine oxide can be isolated in the solid state but the preparative conditions necessary to isolate an adduct of specific stoichiometry are difficult to define; none of acid: base ratio, choice of solvent or reaction temperature are significant factors. Adventitious crystal seeding probably has a dominant role. Both the 1:1 and 1:2 adducts of SnPh2Cl2, but only the 1:1 adduct of SnPh2Br2, were isolated. 1:1 and 1:2 adducts of both SnMe2Cl2 and SnBun2Cl2 were readily isolated whereas only 1:2 adducts were obtained with SnPh2(NCS)2 and SnBun2(NCS)2. SbPh2Cl3 readily forms a 1:1 adduct with triphenylphosphine oxide and the same adduct is obtained from the reaction of the phosphine oxide with SbPhCl2. Crystallographic data are reported for SnPh2Cl2·OPPh3, SnPh2Cl2·2OPPh3, SnPh2Br2·OPPh3 and SbPh2Cl3·OPPh3. Both SnPh2Cl2·OPPh3 and SnPh2Br2·OPPh3 have tin in trigonal bipyramidal environments. 119Sn Mossbauer quadrupole splitting data are consistent with the same trigonal bipyramidal geometry for tin in SnMe2Cl2·OPPh3 whereas the data for the butyl analogue suggest the presence of six-coordinated tin as a result of intermolecular Sn–Cl interactions. A notable feature of all of the adducts subjected to crystallographic studies is the presence of intramolecular π-interactions involving phenyl groups of the phosphine oxide and phenyl groups bonded to the metal.

UV-irradiation of Fe(CO) 3 {P(OPh) 3 } 2 ( 1 ) afforded an orthometallated iron hydride HFe(CO) 2 {P(OPh) 3 }{(PhO) 2 POC 6 H 4 } ( 2 ) which was reacted in situ with alkynes R 1 CCR 2 . Internal alkynes reacted to give either η 2 -alkyne Fe(CO) 2 {P(OPh) 3 } 2 (η 2 -R 1 CCR 2 ) [ 3a , R 1 =R 2 =Ph; 3b , R 1 =Ph, R 2 =CH(OEt) 2 ] or maleoyl Fe(CO) 2 {P(OPh) 3 } 2 {η 1 :η 1 -C(O)C(R 1 )C(R 2 )C(O)} [ 4a , R 1 =Ph, R 2 =Me; 4b , R 1 =R 2 =Me; 4c , R 1 =Me, R 2 =CH(OEt) 2 ; 4d , R 1 =Me, R 2 =CH 2 OH; 4e , R 1 =R 2 =CH 2 OH] complexes. The terminal alkyne HCCPh reacted with 2 to give the ferrole derivative Fe 2 (CO) 4 {P(OPh) 3 } 2 (PhCCH) 2 ( 5 ). The crystal structures of 3a , 4c and 5 were determined. Complex 3a is trigonal bipyramidal about the iron atom with trans apical phosphite ligands and an equatorial arrangement of the CO groups and alkyne CC moiety. Complex 4c is octahedral with trans phosphite ligands and cis carbonyl groups. The alkyne ligand has undergone double carbonylation to generate a ferracyclopentenedione (maleoyl) ring that occupies the remaining two coordination sites at the metal centre. Complex 5 is formally a derivative of Fe 2 (CO) 9 in which an Fe(CO) 2 {P(OPh) 3 } moiety is π-bonded to a ferracyclopentadiene ring arising from the tail-to-tail coupling of two HCCPh ligands.

The hexametallic complex CH2{(η5-C5H4)Fe(CO)2SnPh2(η5-C5H5)Fe(CO)2}2 (3), has been synthesised and its crystal structure determined to exemplify Fe–Sn–Fe bond formation in related polymer systems. A potentially similar product was anticipated from the reaction of [(CH2{(η5-C5H4)Fe(CO)2}2]2− and Ph2SnCl2, however the cyclic complex {CH2(η5-C5H5)Fe(CO)2}2SnPh2 (7), was isolated. The crystal structure of complex 7 shows that there is considerable strain in the ring containing the metal atoms.

[Fe2(η-C5H5)2(L)(CNMe)(μ-CO)(μ-CNMe2)][SO3CF3] where L=CO reacts with HOSO2CF3 in chloroform solution at room temperature (r.t.) to give [Fe2(η-C5H5)2(CO)2{μ-CN(H)Me}(μ-CNMe2)][SO3CF3]2 (reaction (i)). This salt readily and reversibly loses a proton to form [Fe2(η-C5H5)2(CO)2(μ-CNMe)(μ-CNMe2)][SO3CF3] (reaction (ii)) which, in solution, slowly reverts to [Fe2(η-C5H5)2(CO)(CNMe)(μ-CO)(μ-CNMe2)][SO3CF3] under the influence of UV radiation (reaction (iii)) although it can be trapped by reaction with RX (R=H or alkyl; X−=I− or [SO3CF3]−) to give [Fe2(η-C5H5)2(CO)2{μ-CN(R)Me}(μ-CNMe2)][SO3CF3]2 (reaction (iv)). In reactions closely related to (i) and (iii), [Fe2(η-C5H5)2(L)(CN)(μ-CO)(μ-CNMe2)] (L=CO or CNMe) is converted by HOSO2CF3 to [Fe2(η-C5H5)2(L)(CO)(μ-CNH2)(μ-CNMe2)][SO3CF3]2 (reaction (v)); this is reversed by deprotonation and no intermediates are observed (reaction (vi)). The scope and limitations of these reactions have been investigated. Replacement of L by isocyanides shows that the ease with which t-CNR is converted to μ-CN(H)R (reactions (i) and (v)) decreases along the series CNR=CN−/CNH⪢CNXy′(Xy′=C6H3Et2-2,6)>CNMe>CNEt which reflects the μ-seeking ability of the CNR ligands and not their basicity. Reaction (i) does not take place with cis constrained complexes where the two cyclopentadienyl ligands are linked by a –CH2C(O)-group, in donor solvents such as acetonitrile, or with weaker acids such as CF3CO2H or CH3CO2H. Reaction (iii) does not take place when L=CNMe or CNEt, or when μ-CNMe is replaced by μ-CNXy′ even when L=CO. Reaction (vi) always takes place; however, if L=CNMe either it or the t-CO may end-up in the μ-site but the latter is preferred. During reactions (i), (iii), (v) and (vi), cis↔trans isomerism may accompany ligand migration, but the cis is always the predominant product. Spectroscopic data is presented, assigned and used to distinguish between these isomers. Most is straight-forward, but the IR spectrum of [Fe2(η-C5H5)2(CO)2(μ-CNXy′)(μ-CNMe2)][SO3CF3] is very unusual as in solution its ν(μ-C-NXy′) absorption band has a very high frequency,>1900 cm−1, and is very broad, ca. 200 cm−1. The structure of cis-[Fe2(η-C5H5)2(CO)2(μ-CNMe)(μ-CNMe2)][BPh4] has been determined by X-ray crystallography.

A series of 2-, 3- or 4-trifluoromethyl substituted triarylphosphines and their oxide, chalcogenide and Fe(CO)4 derivatives have been prepared and characterised spectroscopically and crystallographically. Electronic effects of CF3 substitution are cumulative and felt equally in the 2, 3 or 4 position. Substitution in the 2 position substantially hinders the complexing ability for steric reasons. Correlated P–C rotation in the 2-substituted derivatives has been analysed by variable temperature NMR and molecular mechanics calculations.

Alkylation of 4,5-diaryl-1,2,3-thiadiazoles and 1,2,3-benzothiadiazoles with trimethylsilylmethyl trifluoromethanesulfonate occurred at N-3. Treatment of the salts with CsF generated new 1,2,3-thiadiazol-3-ium-3-methanide 1,3-dipoles. These gave in situ cycloaddition–rearrangement reactions with some alkyne and alkene dipolarophiles leading to new substituted 1-(2-vinylthioethenyl)pyrazole systems, where a second molecule of dipolarophile was added at the thiol SH which was generated by opening of the thiadiazole ring. 1H, 13C and 15N NMR spectra are reported, as well as X-ray crystal structures on dimethyl 1-{(Z)-2-[(Z)-1,2-bis(methoxycarbonyl)vinylthio]-1,2-diphenylethenyl}-1H-pyrazole-3,4-dicarboxylate 6a and 1-[(Z)-2-cyanoethylthio-1,2-diphenylethenyl]-4,5-dihydro-1H-pyrazole-3-carbonitrile 10. The X-ray data on 6a suggested a weak chalcogen effect from the pyrazole 2-N to the nearby S-atom.

Two equivalents of [Co( η -C 5 H 5 )(PPh 3 ) 2 ] cleave the coordinated C–S bond of [Fe(PPh 3 ) 2 (CO) 2 ( η 2 -SCNR)] complexes to give clusters having the general formulae [{Co( η -C 5 H 5 )} 2 {Fe(CO) 2 (PPh 3 )}(S)(CNR)], I. Those where RNC=(a) MeNC and (b) 4-Me 2 NC 6 H 4 NC exist in both the solid state and in solution as the [{Co( η -C 5 H 5 )} 2 {Fe(CO)(CNR)(PPh 3 )}( μ 3 -S)( μ 3 -CO)] isomer, I I . Those where R=(f) MeC(O)NC, (g) 4-Me 2 NC 6 H 4 C(O)NC and (h) C 6 H 5 C(O)NC exist as the [{Co( η -C 5 H 5 )} 2 {Fe(CO) 2 (PPh 3 )}( μ 3 -S)( μ 3 -CNR)] isomer, I II , and those where RNC=(c) 4-MeC 6 H 4 NC, (d) C 6 H 5 NC and (e) 4-ClC 6 H 4 NC exist as a mixture of I I and I II in fluxional equilibrium in solution with the proportion of I II increasing with increasing electron-withdrawing ability of R. Variable temperature 1 H-NMR spectroscopy shows that apart from the I I =I II interconversion (Δ G * =ca. 77–88 kJ mol −1 ), the I I isomer undergoes a further fluxional process which inverts the configuration at Fe (ΔG * =ca. 65 kJ mol −1 ). All I react with MeOSO 2 CF 3 to give salts of the [{Co( η -C 5 H 5 )} 2 {Fe(CO) 2 (PPh 3 )}( μ 3 -S){ μ 3 -CN(Me)R}] + cations except for Ig which is alkylated at the NMe 2 group to give [{Co( η -C 5 H 5 )} 2 {Fe(CO) 2 (PPh 3 )}( μ 3 -S)( μ 3 -CNC(O)C 6 H 4 NMe 3 ] + . The new complexes are characterized by IR and NMR spectroscopy, and by X-ray crystallography for [{Co( η -C 5 H 5 )} 2 {Fe(CO)(CNC 6 H 4 Me-4)(PPh 3 )}( μ 3 -S)( μ 3 -CO)], Ic, and [{Co( η -C 5 H 5 )} 2 {Fe(CO) 2 (PPh 3 )}( μ 3 -S){ μ 3 -CNC(O)C 6 H 5 }], Ih. In both the structure is based on a FeCo 2 triangle capped on one face by a μ 3 -S ligand and on the other by a μ 3 -CNC(O)Ph (Ih) or μ 3 -CO (Ic) ligand with S and CO are disordered in Ic. In both cases the C ligand acts as a 2e donor in these 48e complexes. The bridging isocyanide ligand is bent at N indicating that it is acting as a strong electron acceptor, unlike the μ 3 -CNMe ligand in [Ni 3 (Ph 2 PCH 2 PPh 2 ) 2 (CNMe) 2 ( μ 3 -I)( μ 3 -CNMe)] + which is almost linear and probably only a weak acceptor but a strong donor.

The reaction of Fe(CO)2(η2-CS2){P(OPh)3}2 1 with two equivalents of PBu3 in a minimum volume of a polar solvent such as acetonitrile or dimethylsulfoxide afforded the thiocarbonyl derivative Fe(CO)2(CS){P(OPh)3}2 2 in ca. 80% yield whereas reaction in solvents such as dichloromethane or benzene afforded the substitution products Fe(CO)2(η2-CS2){P(OPh)3}(PBu3) and Fe(CO)2(η2-CS2)(PBu3)2. Although desulphurization of Fe(CO)2(η2-CS2){P(OR)3}2 by PBu3 in polar solvents is not a general route to Fe(CO)2(CS){P(OR)3}2 for all R, the new compound Fe(CO)2(CS){P(OEt)3}2 has been obtained and characterised spectroscopically. The crystal structures of 2 and Fe(CO)3{P(OPh)3}2 were determined and are very similar. Both compounds are trigonal bipyramidal about the Fe atom with trans apical phosphite ligands and a trigonal planar arrangement of CO/CS groups. The CS ligand in 2 was found to be disordered over two sites with occupancies 0.63 and 0.37.

The reaction of [Fe(CO)2(PPh3)2(η2-CS2)] with two equivalents of [Co(η-C5H5)(PPh3)2] gives [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CS)] (L=PPh3) as the sole product in good yield. Under the same conditions, [Fe(CO)2(L)2(η2-CS2Me)][SO3CF3] gives [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CSMe)][SO3CF3]. The PPh3 ligand of [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CS)] (L=PPh3) may be replaced by P(OPh)3 and P(OMe)3 on UV photolysis to give the complexes where L=P(OPh)3 and P(OMe)3, but no isolable products were formed when L=CO, CNMe, PMe3 or PBu3n. The three clusters react with RI and ROSO2CF3 (R=Me, Et or allyl) to give [{Co(η-C5H5)}2{Fe(CO)2(L)}(μ3-S)(μ3-CSR)]+ salts, and there is spectroscopic evidence for the formation of the [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CSMe2)]2+ cation. The molecular structures of [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S)(μ3-CS)] and [{Co(η-C5H5)}2{Fe(CO)2(PPh3)}(μ3-S){μ3-CSMe}][I] have been determined by X-ray diffraction methods, and shown to be based on a Co2Fe triangle capped on one face by a μ3-S ligand and on the other face by a μ3-CS or μ3-CSMe+ ligand acting as a two-electron donor to the cluster. In the salt there are two cations whose structures differ slightly. In general, bond lengths are normal, but those to iron are always longer than those to cobalt.

1,3,4-Thiadiazolium-3-(unsubstituted) methanides have been trapped with substituted alkyne dipolarophiles at –60 °C giving high yields of 2,3-di- and 2,3,4-tri-substituted 1-{[1-(vinylthio)-1-phenylmethylidene]amino}pyrroles from a cycloaddition rearrangement sequence. The conformation of these molecules results in an unusual proton shielding effect in the 1H NMR spectra. An X-ray crystal structure is reported for methyl 1-{(Z)-1-[(Z)-2-methoxycarbonylvinylthio]-1-phenylmethylideneamino}-2-phenyl-1H-pyrrole-3-carboxylate 7a.

In cycloaddition reactions of phthalazinium-2-methanide and aryl(3-phenylprop-2-en-1-ylidene)ammoniomethanide 1,3-dipoles with thiobenzophenone, phenyl dithioacetate and methyl cyanodithioformate the regiochemistry was such that the nucleophilic methanide terminus of the dipole bonded to the sulfur atom, thus giving stereoisomeric substituted thiazolo[4,3-a]phthalazines and 4-styryl substituted tetrahydrothiazoles. With dicyclopropyl thioketone and thioadamantanone, steric effects caused a gradual reversal of this regiochemistry. Solvent polarity did not alter the distribution of regioisomers. X-Ray crystal structures are reported for 1,1-diphenyl[1,3]thiazolo[4,3-a]phthalazine 7 and 3-(p-bromophenyl)-4-[(E)-styryl]-5-trans-cyano-5-cis-methylthio-2,3,4,5-tetrahydrothiazole 15b.

Two new functionalized tetramethylcyclopentadiene (FTMCP) ligands are described: optically active (1S)-1-(6-methoxynaphthalenyl)-1-(2,3,4,5-tetramethylcyclopentadienyl)ethane (2) and racemic 1-met...

(R)-(+)-Ferrocene cyanohydrin acetate, obtained by enzymatic acylation of ferrocene cyanohydrin, may be transformed by reduction and alkylation into novel ferrocenyl β-aminoalcohols. Substitution of acetate by methanolic HNMe2 proceeds with racemisation, but significant diastereoselection is observed on Strecker reaction using (−)-PhCH(Me)NHMe.

The symmetrical dimers [(C5H5)Fe(CO)2]2 (1), [(C5Me5)Fe(CO)2]2 (2), and [(C5Me4H)Fe(CO)2]2 (3) have been used to synthesize the unsymmetrical dimers (C5Me4H)(C5H5)Fe2(CO)4 (4), (C5Me5)(C5H5)Fe2(CO)4 (5), and (C5Me5)(C5Me4H)Fe2(CO)4 (6). All of the new compounds show cis/trans isomerization to varying extents, depending on the degree of substitution. The crystal structures of 3 and 4 have been determined. The limit of the observable cis-bridged isomer is found in 6 which is 14% cis in CH3CN solution.

Reactions of 2-methyl-1,2,5-oxadiazolium perchlorate salts and 1-methyl-2-aryl-1,2,3-triazolium perchlorate salts with the bases KCN, NaOEt, KOBut, LiNPri2 give ring expansions to substituted 1,2,5-oxadiazines and 1,2,4-triazines. With cyanide as base the reactions follow an addition–elimination pathway and in two cases the addition intermediate has been isolated or directly detected by low-temperature NMR spectroscopy. The oxadiazolium system with cyanide also gives a useful new route to α-cyano nitrones via a ring degradation which competes with ring expansion. The reactions with KOBut and LiNPri2 do not involve an addition of the base to the azolium salt. Reactions have been monitored by 13C NMR spectroscopy by using 13CN–. An X-ray crystal structure is reported for (E)-N-(α-cyanobenzylidene)methylamine N-oxide.

New routes to substituted phenanthro[9,10-e]-1,2,4-triazines and phenanthro[9,10-c]-1,2,5-oxadiazines are described. Cycloadditions of these with C-phenyl-N-p-nitrophenylnitrile imide [IUPAC name: 2-benzylidene-1-(p-nitrophenyl)hydrazin-2-ium-1-ide] gave new substituted spiro-tricyclic phenanthro-1,2,4-triazolo[4,3-d][1,2,4]triazines and phenanthro-1,2,4-triazolo[3,4-d][1,2,5]oxadiazines. An X-ray crystal structure is reported on 7,10-diphenyl-5-(4′-nitrophenyl)-9,10-dihydro-5H-phenant hro[9,10-e][1,2,4]triazolo[4,3-d][1,2,4]triazine 5a.

Barriers to metal-arene ring rotation in [1,4-C6H4(SiMe3)2)Cr(CO)2PPh3 and (1,3,5-C6H3tBu2)Cr(CO)2PPh3 are lowered relative to a previously reported barrier of 32 J mol−1 for (1,4-C6H4tBu2)Cr(CO)2PPh3. Reasons for the decreased barriers are discussed in the light of crystal structure determinations of these complexes.

Racemic 2-hydroxymethyl-1-phenylthioferrocene 5 and 2-hydroxymethyl-1-tert-butylthioferrocene 6 were subjected to kinetic resolution via acetylation catalysed by lipase from Candida antarctica (Novozym® 435) or Mucor miehei (Lipozyme® IM). The obtained enantiopure thioethers underwent chemical oxygenation at the sulfur atom to give the corresponding ferrocenyl sulfoxides with settled central/planar chirality.

A variety of cyclic and acyclic [(pentadienyl)Fe(CO)2L]X complexes (L = CO, PPh3) containing terminal acyloxy or alkoxy substituents have been prepared. In situ NMR studies indicate that for the acyclic series where L = CO, stability is limited by solvolysis reactions. The position of nucleophilic attack (ipso for alkoxy, internal for acyloxy) in the acyclic series indicates an electron-donating and electron-withdrawing nature for alkoxy and acyloxy substituents, respectively. In the cyclic series, the different regiodirecting powers of alkoxy and acyloxy groups provide access to regioisomeric substituted cyclohexadienyl salts. Crystal structures of the Ψ-exo and Ψ-endo stereoisomers of [5-(benzoyloxy)-2,4-hexadien-1-ol]Fe(CO)2PPh3 (34 and 35) and of [(1,3,4,5-η)-1-(benzoyloxy)-2-methyl-3-pentene-1,5-diyl]Fe(CO)2PPh3 (57) have been determined.

Hydrolysis using pig liver esterase of (benzene-1,2-diacetic ester)Cr(CO) 3 complexes generates the half-ester in high enantiomeric purity. The high enantioselectivity may be rationalised through substrate interaction with the Jones active site model of pig liver esterase.

A range of new fused ring systems based on phenanthrene were obtained from cycloaddition–rearrangement reactions of 9,10-bisarylazophenanthrenes with alkyne and dipolarophiles. These new rings include substituted phenathro[9,10-e]-1,2,3-triazines, the tricyclic systems, substituted 3a,6a-(biphen-2,2′-yl)hexahydropyrrolo[2,3-d]-1,2,3-triazoles and substituted 3a-6a-(biphen-2,2′-yl)-hexahydroimidazo[4,5-d]-1,2,3-triazoles. X-Ray crystal structures are reported on 2-(p-bromophenyl)-4-methoxycarbonyl-4-(p-bromophenyliminomethoxalyl)-3,4-dihydrophenanthro[9,10-e]-1,2,3-triazin-2-ium-3-ide 6b, and 2,4-diphenyl-3a,6a-(biphen-2,2′-yl)-5,6-endo-dicarboxy-N-phenylimido)-1,3a,4,5,6,6a-hexahydropyrrolo[2,3-d]-1,2,3-triazol-2-ium-1-ide 11a.

The preparation of a pyrrolo[ 1,2-a]benzimidazole, pyrido[1,2-a]benzimidazole and pyrrolo[1,2-a]benzimidazolequinone containing a fused cyclopropane ring is reported. Their synthesis involved the thermolysis of the respective benzimidazole-2-Eschenmoser hydrazones (aziridinyl imines), which facilitated an intramolecular 1,3-dipolar cycloaddition. X-ray crystal structure of one [3+2] pyrazoline-cycloadduct is presented. The redox potential of -1.052 V (vs. ferrocene) for the cyclopropapyrrolo[1,2-a]benz-imidazolequinone was determined by cyclic voltammetry indicating single-electron reduction occurs more easily than mitomycin C or the cyclopropamitosenes.

Reactions of diorganotin(IV) dinitrates with M(3MeO-sal1,3pn) · H 2 O (M = Ni, Co or Zn; H 2 3MeO-sal1,3pn = N , N ′-bis(3-methoxysalicylidene)propane-1,3-diamine) leads to nitrate migration from tin to the transition metal or zinc and the formation of intimate ion-paired bimetallic 1 1 addition complexes. In each of these complexes the tin atom is located in the plane of the Schiff-base oxygens and is coordinated by all four. The complexes [SnBz 2 (NO 3 )] · [M(3MeO-sal1,3pn)(NO 3 )](M = Co or Zn) are isomorphous and each contains tin in a pentagonal bipyramidal environment with the four Schiff-base oxygens and a nitrate oxygen defining the equatorial plane. In the case of {[SnMe 2 ] · [Ni(3MeO-sal1,3pn)(NO 3 )(H 2 O)]}NO 3 , the tin is six-coordinated, but there is an additional weak intermolecular SnO interaction involving an oxygen of a nitrate coordinated to nickel. The complex {[SnMe 2 (H 2 O)] · [Co(3MeO-sal1,3pn)(NO 3 )(H 2 O)]}NO 3 contains tin in a pentagonal bipyramidal environment with the Schiff-base oxygens and a water oxygen defining the equatorial plane. The crystal structures of both dimethyltin complexes display extensive hydrogen bonding.

The quadruply bonded chiral anion [Re2Cl7PBzMePh]− (Bx = Ch2Ph) was synthesized and its crystal structure was determined. It crystallized in space group P1 with unit cell dimensions a = 10.677(2), b = 12.220(2), c= 18.220(4) A, α = 85.66(2), β = 75.98(2) and γ = 80.07(2)°. The ReRe distance was 2.2196(8) A. The average twist angle χ was 11.6°. The δ-bond energy was determined by molecular modelling to be 9 kcal mol−1 and 5% greater than the energy required to eclipse [Re2Cl8]2−.

[Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO) 2 (μ-CO) 2 ] reacts with CNMe in refluxing xylene when A-B = R , S -CH(NMe 2 )CH(NMe 2 ) or CH 2 C(O) to give [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO) 4− n (CNMe) n ] ( n = 1 or 2). This thermal reactiin does not take place when A-B = R , R / S , S -CH(NMe 2 )CH(NMe 2 ), CH 2 CH(NMe 2 ), CHC(NMe 2 ), CH 2 CH(OH) or CH 2 CH 2 , but photolysis allows the preparation of [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO) 4− n (CNMe) n ] ( n = 1–3), and [Fe 2 η,η-C 5 H 4 CH 2 CH(OH)C 5 H 4 (CO) 3 (CNMe)] may be prepared by the LiAlH 4 -reduction of [Fe 2 η,η-C 5 H 4 CH 2 C(O)C 5 H 4 (CO) 3 (CNMe)]. All the complexes react with MeI, EtI or MeOSO 2 CF 3 to give derivatives containing one or two μ-CNMe 2 + ligands. 1 H MMR studies show that all the neutral complexes are fluxional, with processes taking place within the C 5 H 4 -A-B-C 5 H 4 ligands comparable to those observed in the tetracarbonyl precursors as well as CO/CNMe site exchange. This last is more restricted than in the [Fe 2 (η-C 5 H 5 ) 2 (CO) 4− n (CNMe) n ] counterparts, so that two non-interconverting [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO) 2 (CNMe) 2 ] species are possible, and have been separated in most instances; one has the structure [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO)(CNMe)(μ-CO) (μ-CNMe)] and the other is [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CO) 2 (μ-CNMe) 2 ], which is in equilibrium with [Fe 2 η,η-C 5 H 4 -A-B-C 5 H 4 (CNMe) 2 (μ-CO) 2 ] in solution. Their formation provides unequivocal evidence for the validity of the Cotton-Adams rules on fluxionality in [Fe 2 (η-C 5 H 5 ) 2 (CO) 4 ] derivatives. The structure of R , S -[Fe 2 η , η -C 5 H 4 CH(NMe 2 )C 5 H 4 (CO) 2 ( μ -CNme) 2 ] has been determined by an X-ray diffraction study.

Reaction of [{Co(CO)4}2SnX2] (X = Cl, Br or I) with bicycio [2.2.1] hepta-2,5-diene, C7H8, and a variety of 1,3-dienes has allowed the isolation of [{Co(η4-C7H8)(CO)2}{Co(CO)4}SnX2], [{Co(η4-C7H8)(CO)2}2SnX2] and [{Co(η4-C6H10)(CO)2}2SnCl2] only (C6H10 = 2,3-dimethylbuta-1,3-diene). An X-ray diffraction study of [{Co(η-C6H10)(CO)2}2SnCl2] has shown that in this complex there is distorted tetrahedral coordination about Sn arising from the different electronegativities of its substituents. The coordination about cobalt is most simply described as distorted trigonal bipyramidal (tbp) the first time that this stereochemistry has been found in a five-coordinated d8 metal complex containing an η4-(1,3-diene) ligand. The Sn occupies an axial site, and the diene is as near to axial-equatorial as it can be. However, as a consequence of the size and shape of the diene, whereas the midpoint of its C(3)-C(4) bond lies close to the equatorial plane, that of its C(1)-C(2) bond does not lie on the Sn-Co axis. The coordination is distorted from tbp towards square-based pyramidal (sp). It is shown that rotation of the diene about an axis through its centroid and the cobalt atom leads in turn to various tbp and sp structures and distortions thereof. In all these the diene is coordinated axial-equatorial (tbp) or basal-basal (sp), but the other three ligands occupy the other coordination positions in turn.

Two [Fe(η 4 -C 7 H 8 )(CO) 2 (L)] complexes (C 7 H 8 = norbornadiene) have been prepared and their structures determined by X-ray diffraction. When L = CNMe, the coordination about Fe is best described as trigonal bipyramidal with the apical positions occupied by CNMe and one CC. It is distorted towards square pyramidal, in part due to the short ‘bite’ of the C 7 H 8 ligand. When L = PPh 3 , a similar distortion is found, but it is so great that the coordination about Fe is close to square pyramidal, with an apical CO ligand. The relevance of these structures to the rotation of the diene ligand in [Fe(η 4 -diene)(CO) 3 ] complexes is discussed.

The structure of [CO3(η-C5H5)3(μ3-S)(μ3-CNC6H4Me-4)] has been determined by a X-ray diffraction study and shown to be similar to that of [Co3(μ-C5H5)3(μ3-S0(μ3-CNEt)]. The μ3-CNC6H4Me-4 ligand acts as a 2e donor, but back bonding to it results in bending at N, differentiation of its two C-N π★ orbitals, and formation of a ‘pseudo’ mirror-plane in the molecule. The consequent distortions within the CCO3(S) ‘trigonal bipyramid’ are significant and suggest that a [{Co(η-C5H 5)(t-CNC6H4Me4)}{Co2(η-C5H5)2(μ2-S)}] mesomer contributes towards an overall description of the bonding within the molecule.

The interactions of SnR 2 X 2 (R  Me, Et, n Pr, n Bu; X  Cl, Br, NCS) with pyrazine (L) have been investigated in both chloroform and acetonitrile. Equilibrium constants have been determined by using 119 Sn chemical shifts and the computer program eqnmr . In chloroform, Sn n Bu 2 Cl 2 and Sn n Bu 2 Br 2 form complexes of composition ML and ML 2 , with ML the dominant species. In acetonitrile all of the tin(IV) complexes form only the 1:1 adducts (ML). Thermodynamic parameters have been determined for these systems in both solvents.

Unlike diorganotin(IV) dihalides, triphenyl- and tribenzyl-tin chlorides do not react with Schiff-base complexes M(SB) (M  Cu II , Ni II and Zn II ; SB  N , N ′-ethylenebis-salicylideneaminato and related salicylaldimine ligands). Triphenyltin chloride does however form 1:1 addition complexes with 3,3′-methoxy substituted salicylaldimines of Ni II and Cu II , but only in the presence of water. Each of these complexes contains the aquo adduct SnPh 3 Cl · H 2 O, with the donor water molecule engaged in hydrogen bonding interactions with the four oxygen atoms of the divalent metal salicyaldimine. These structural features were confirmed crystallographically for (SnPh 3 Cl · H 2 O)Ni(3-MeOsal1,3pn) (1:1) [H 2 3-MeOsal1,3pn  N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine]. In the case of [SnPh 3 Cl · H 2 O][Ni(3-MeOsal1,3pn) · H 2 O] (1:1) both the water molecule coordinated to nickel and the water molecule coordinated to tin engage in hydrogen bonding interactions with the Schiff-base oxygen atoms, thereby creating centrosymmetric hydrogen-bonded dimers.

Iron pentacarbonyl reacts with 6-dimethylaminofulvene in refluxing xylene to give three products, 1 , 2 and 3 . Compound 1 is R , S -[Fe 2 η,η-C 5 H 4 CH(NMe 2 )CH(NMe 2 )C 5 H 4 (CO) 2 (μ-C0) 2 ], 2 is its R , R / S , S isomer, and 3 is [Fe 2 η 3 ,η 5 -Me 2 NCHC 5 H 3 CHC 5 H 4 (CO) 5 ]. Compound 3 is favoured by high reactant concentrations and an excess of [Fe(CO) 5 ]. Analogues of 2 and 3 but not 1 may be prepared by using 6-Me(Ph)NCHC 5 H 4 , 6-Et 2 NCHC 5 H 4 and 6- i Pr 2 NCHC 5 H 4 ; the last of these also gives the unlinked dimer [Feη 5 -C 5 H 4 CH 2 N i Pr 2 2 (CO) 2 (μ-CO) 2 ]. This behaviour is attributed to the steric effects of the NR 2 groups on the formation of the ring- linking C-C bond. Dynamic NMR studies show that in 1 , but not 2 , there is a slowable restricted rotation about this bond and, in both 1 and 2 , rotation- inversion about the nitrogen atoms of the NMe 2 groups can be slowed. Compounds 1 and 2 are derivatives of a 1,2-bis-dimethylaminoethane, and as such have an extensive organic chemistry that leaves the Fe 2 (CO) 2 (μ-CO) 2 moieties intact. There are differences between 1 and 2 , due to conventional stereochemical effects, and consequently the Fe 2 (CO) 2 (μ-CO) 2 fragments are involved in some instances; this leads to unexpected and unusual reactions. The structures of 2 and the ketone [Fe 2 (η,η-C 5 H 4 CH 2 C(O)C 5 H 4 (CO) 2 (μ-CO) 2 ] have been confirmed by X-ray diffraction studies and are compared with that previously reported for 1 .

The synthesis and crystal and molecular structures of the platinum(II) complex Pt(HL)Cl where H2L is the diacid diamide –[CH2N(CH2COOH)CH2CONH2]2, a hydrolytic metabolite of an antitumour active bis(3,5-dioxopiperazin-1-yl)alkane are reported. The complex is square planar and contains HL− as a tridentate 2N (amino), O (carboxylate) donor. The metal to ligand bond distances are Pt-Cl 2.287(1) Å, Pt-O 2.002 (1) Å, Pt-Ntrans Cl 2.014(1) Å and Pt-Ntrans O 2.073 Å. There is extensive hydrogen bonding, each molecule of Pt(HL)Cl being intermolecularly hydrogen bonded to ten others giving a 3-dimensional network. There is also one intramolecular H-bond.