John R. Moss

Recent developments in the activation of carbon dioxide by metal complexes

Abstract World leaders are negotiating a new global treaty that will lead to the reduction of global greenhouse gas emissions to legal commitments. Carbon dioxide is the largest single source of greenhouse gas, and emissions of carbon dioxide are increasing continuously. Utilization of carbon dioxide as a possible starting material for the synthesis of fine chemicals provides an attractive alternative to compounds presently derived from coal and petroleum. The effective conversion of carbon dioxide to useful chemicals will inevitably rely on transition metal catalysts. This review covers the recent progress in the direct activation of carbon dioxide by organo-transition metal complexes, with emphasis on insertion reactions and oxidative coupling reactions of carbon dioxide.

Synthesis and antiplasmodial activity in vitro of new ferrocene–chloroquine analogues

The synthesis of the new compounds (7-chloroquinolin-4-yl)-N′-(1′-dimethylaminomethylferrocen-1-ylmethyl)-amine (4a) and N-(7-chloroquinolin-4-yl)-N′-(1′-dimethylaminomethylferrocen-1-ylmethyl)-ethane-1,2-diamine (6a) is reported. The key step in the synthesis is the cleavage of a ferrocene–Sn bond with n-BuLi to give a lithiumferrocenide species (10), which is then treated with an electrophile. Thus, 1′-dimethylaminomethyl-1-tri-n-butylstannyl-ferrocene (11) and subsequently 1′-dimethylaminomethylferrocene-1-carbaldehyde (7a) were synthesised from 1,1′-bis(tri-n-butylstannyl)ferrocene, employing [CH2NMe2]I and DMF to introduce the amine and then the aldehyde functionalities. In addition, the compound 1′-dimethylaminomethyl-1-lithiumferrocenide was isolated and the 1H and 13C NMR data are reported. X-Ray crystal and molecular structures are reported for compound 4a and the related compound N-(7-chloroquinolin-4-yl)-N′-(2-dimethylaminomethylferrocen-1-ylmethyl)-ethane-1,2-diamine (5a). The antiplasmodial activity in vitro against chloroquine sensitive and resistant strains of Plasmodium falciparum is reported and compared to a series of ferrocene, ruthenocene and phenylene analogues.

Organometallic chemistry and surface science: mechanistic models for the Fischer–Tropsch synthesis

Abstract The Fischer–Tropsch synthesis is an industrially important process for the conversion of synthesis gas (CO/H2) into hydrocarbons and oxygenates. Synthesis gas can be obtained from coal or natural gas. Organometallic model complexes and surface science techniques have been widely used to obtain mechanistic information about this heterogeneous process. A review of the mechanisms for the Fischer–Tropsch synthesis and the evidence for these mechanisms is presented. It is generally accepted that the Fischer–Tropsch reaction may be viewed as a polymerisation of surface methylene (CH2) species, which are formed by the dissociation and hydrogenation of CO on the catalyst surface. The alkyl mechanism proposes that the reaction is initiated by the formation of a surface methyl species, and that chain growth takes place by successive insertions of methylene into the metal-alkyl bond. The alkenyl mechanism proposes that the formation of a surface vinyl species (CHCH2) initiates chain formation, and that chain growth is facilitated by methylene insertion into the metal-vinyl bond to form an allyl species (CH2CHCH2). The allyl species isomerises to form a surface alkenyl (CHCHCH3) which may propagate further. These mechanisms are discussed.

New amine and urea analogs of ferrochloroquine: synthesis, antimalarial activity in vitro and electrochemical studies

Amine and urea analogs of ferrochloroquine with varying methylene spacer lengths were synthesised, studied by cyclic voltammetry and evaluated in vitro against a sensitive (D10) and resistant (K1) strain of Plasmodium falciparum. Most analogs were found to be more active than chloroquine in both strains. In D10 ureas were more active than amines and antimalarial activity in this strain correlated well with the length of the methylene spacer and redox potentials. The length of the methylene spacer was a major determinant of antimalarial activity in K1.

Synthesis and antimalarial activity in vitro of new ruthenocene–chloroquine analogues

The syntheses of the new compounds (7-chloroquinolin-4-yl)(2-dimethylaminomethylruthenocen-1-ylmethyl)amine 3 and N-(7-chloroquinolin-4-yl)-N′-(2-dimethylaminomethylruthenocen-1-ylmethyl)ethane-1,2-diamine 5 are reported. The reactions are compared to those previously reported for the preparation of the ferrocene analogues. The key step in the reaction is the regioselective synthesis of 2-dimethylaminomethylruthenocene carboxaldehyde 10 by deprotonation of dimethylaminomethylruthenocene with t-BuLi in diethyl ether, followed by the addition of DMF. In addition, 1′-dimethylaminomethylruthenocene carboxaldehyde 11 was also prepared leading to the unexpected synthesis of the 1,1′-isomers (7-chloroquinolin-4-yl)(1′-dimethylaminomethylruthenocen-1-ylmethyl)amine 17 and N-(7-chloroquinolin-4-yl)-N′-(1′-dimethylaminomethylruthenocen-1-ylmethyl)ethane-1,2-diamine 18. X-Ray crystal and molecular structures for compounds 3 and 17·H2O are reported. The 4-aminoquinoline complexes show high efficacy against the chloroquine sensitive and resistant strains of the Plasmodium falciparum parasite in vitro; these results are compared with those obtained for the analogous ferrocene compounds.

Haloalkyl complexes of the transition metals : I. The synthesis and some reactions of the haloalkyl complexes formed by the reaction of sodium (pentahapto-cyclopentadienyl)dicarbonyliron with α, ω-dihaloalkanes

Abstract The reactions of Na[CpFe(CO) 2 ] (Cp = η 5 -C 5 H 5 ) with α, ω-dihaloalkanes at −20°C yield ω-haloalkyl complexes of the type CpFe(CO) 2 (CH 2 ) n X ( n = 3, 4 or 5, X = Br; n = 3, X = Cl). CpFe(CO) 2 (CH 2 ) n Br reacts with Na[CpFe(CO) 2 ] to give the known binuclear complexes [CpFe(CO) 2 ] 2 [μ-(CH 2 ) n ] ( n = 3, 4 or 5) and with Na[CpMo(CO) 3 ] to give the mixed metal complex CpFe(CO) 2 [μ-(CH 2 ) 3 ]CpMo(CO) 3 ]. Triphenylphosphine reacts with CpFe(CO) 2 (CH 2 ) 3 Br in refluxing acetonitrile to give the carbene cation [CpFe(CO)(PPh 3 )CovtsqbCOCH 2 CH 2 C H 2 ] + , isolated as the PF 6 − and BPh 4 − salts, and the cationic acyl complex [CpFe(CO)(PPh 3 )CO(CH 2 ) 3 PPh 3 ] + Br − .

The synthesis and properties of heterodinuclear alkanediyl complexes of iron(II) containing molybdenum(II), tungsten(II), rhenium(I) and ruthenium(II)

Abstract The reactions of the iodoalkyl compounds [(η5-C5R5)Fe(CO)2{(CH2)nI}] with Na[MLy] yield the new heterodinuclear alkanediyl compounds [(η5-C5R5)-(CO)2Fe(CH2)nMLy] (where R = H: MLy = Mo(CO)3Cp, W(CO)3Cp, Re(CO)5, n = 3–6; R = CH3: MLy = Ru(CO)2Cp, n = 3–5; Re(CO)5, n = 4). The related mixed ligand complex [Cp(CO)2Fe(CH2)3Fe(CO)2CP★] has also been prepared (where Cp = η5-C5H5 and Cp★ = η5-C5(CH3)5). The new compounds have been fully characterised by analytical and spectroscopic methods.

Halogenoalkyl Complexes of Transition Metals

Publisher Summary This chapter focuses on halogenoalkyl transition metal complexes, particularly monohalogenoalkyl transition metal complexes. Halogenoalkyl transition metal complexes of type [L y M((CH 2 ) n X)] (L y = ligands, M = transition metal, X = C1, Br, I, or F, n ≥ 1) are less well known, although they have recently been recognized as a separate class of alkyl compounds. Complexes [L y M((CH 2 ) n X)] can either be considered as simple examples of functionalized alkyl compounds of transition metals or as metal-substituted alkyl halides. Complexes of the type [L y MCH 2 X] can be useful precursors to methylene complexes [L y M=CH 2 ] + hydroxymethyl complexes [ L y MCH 2 OH] and methylene-bridged complexes L y MCH 2 M’L x all of which have been implicated in many catalytic processes. The monohalogenoalkyl complexes have a functionality on carbon, they have additional reactivity potential compared to the alkyl analogs. Thus, the halogenoalkyl complexes show interesting and novel chemistry and can be used, for example, as precursors for many important classes of compounds—including acyclic and cyclic carbene complexes, homo- and heterobimetallic hydrocarbon-bridged compounds, as well as a range of other important functionalized alkyl compounds.

Some evidence refuting the alkenyl mechanism for chain growth in iron-based Fischer–Tropsch synthesis

Abstract Recently, Maitlis et al. [J. Catal. 167 (1997) 172] proposed an alternative reaction pathway for chain growth in the Fischer–Tropsch synthesis. In this mechanism, chain growth is assumed to occur by methylene insertion into a metal–vinyl bond, forming an allyl species that will subsequently isomerise to a vinyl species. Organo-metallic allyl complexes, Fe{[η 5 -C 5 H 5 ](CO) 2 CH 2 CHCH 2 } and Fe{[η 5 -C 5 (CH 3 ) 5 ](CO) 2 CH 2 CHCH 2 } were synthesised. Under thermal treatment, the decomposition of these complexes was observed, instead of the isomerisation. In a hydrogen atmosphere, the reduction of the iron–carbon bonds and the hydrogenation yielding iron–alkyl species was observed. This clearly shows that the proposed vinyl–allyl isomerisation is unlikely to occur in mono-nuclear iron complexes. Hence, it might be expected that the reaction mechanism proposed by Maitlis et al. [J. Catal. 167 (1997) 172] is unlikely to be the main route for chain growth in the Fischer–Tropsch synthesis.

Organometallic and related metal-containing dendrimers

Reports of the synthesis of new dendrimers containing organometallic fragments have increased dramatically over the past few years and examples of dendrimers containing many different metals are now known. This article highlights some of the the ways in which transition metals and their ligand systems have been incorporated into the growing number of dendrimers. Some structural details and properties of metal-containing dendrimers are described, and their applications are also discussed. The cover illustration shows Table Mountain, South Africa and a fourth generation ruthenium dendritic wedge.