Michael. Mlekuz

Dicyclopentadienylnickel: A problematical reagent in cluster synthesis

Abstract The room temperature reaction of (C5H5)2Ni with Co3(CO)9CR, where R is CO2CH(CH3)2, gives almost quantitative replacement of a Co(CO)3 group by a (C5H5)Ni fragment. However, the same reagents in refluxing THF do not lead to further replacement of Co by Ni but instead yield the products (C5H5)3-Co3(CO)(H)CR and (C5H5)3Co2Ni(CO)CR in which carbonyl groups have been replaced by cyclopentadienyl ligands. The isolobal nature of the fragments in these complexes is noted.

Mixed metal acylium clusters: A chemical and spectroscopic study

Abstract The generation of mixed metal acylium cations [MCo2(CO)6CCO]+, M = (C5H5Mo(CO)2, (C5Me5)Mo(CO)2 and (C5H5, from the parent esters via treatment with HPF6 in propionic anhydride is described. These cations and also the related [(C5H5)2Co3(CO)4CCO]+ cluster react with alcohols to give esters and with indole or pyrrole to give Friedel-Crafts type products. 1H NMR, IR and FAB mass spectroscopic data are reported.

CpMoCo2(CO)8CCO+: Synthesis and characterization of a mixed metal acylium cation

Abstract CpMoCo2(CO)8CCO2CHMe2 in propionic anhydride reacts with HPF6 to yield the mixed metal acylium cation CpMoCo2(CO)8CCO+ which reacts with a variety of nucleophiles, e.g., ROH, R2NH, yielding cluster-bound esters and amides, respectively. The cation also reacts with PhNMe2 in a Friedel-Crafts process. In the presence of water, Co3(CO)9CCO+ can also decompose to yield the neutral dimer [(Co3(CO)9C]2.

Fluxionality of M2C2 tetrahedral clusters containing cyclopentadienyldicarbonylmetal vertices: Unexpectedly different behaviour of molybdenum and tungsten analogues

Abstract The syntheses of a series of molecules [Cp′M(CO)2]2(RCCR′), where Cp′ = C5Me5, C5H4Me; M = Mo, W; R = Ph, R′= H, Et, CO2Me, SnMe3 are described. The molybdenum complexes possess a semi-bridged carbonyl thus rendering the molecules chiral; their 13C NMR spectra show four carbonyl resonances and two cyclopentadienyl environments. The barrier to racemisation depends on the bulk of the substituents on the ring. In contrast, the NMR spectra of the tungsten analogues show only single carbonyl and cyclopentadienyl environments even at −90°C and 9.4 T.