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Electrospray mass spectrometric analysis of transition metal carbonyl clusters

A key objective of this thesis was to develop Electrospray (Ionisation) Mass Spectrometry (ESMS) within organometallic chemistry, specifically as a technique for investigating transition metal carbonyl cluster chemistry. An initial survey of air-sensitive high-nuclearity rhodium and nickel clusters, such as [Rh9As(C0)21f and [H2Ni!2(CO)iif, demonstrated the usefulness of ESMS for characterisation. ESMS was applied to monitoring the reactions of ~-E[M2(CO)xh [E = Si, Ge, Sn; M = Co (x = 7), Fe (x = 8)] with anionic transition metal carbonyl reagents. Analysis of the reaction between ~-Ge[Coi(C0)7h and [Co(C0)4r revealed the inter-conversion processes between previously isolated clusters, and was crucial in identifying the unheralded [Co10Gei(C0)24f product. Conditions for optimal yields of this anion were established and the cluster subsequently isolated and structurally characterised (below). The core structure of [Co10Ge2(C0)24f is unprecedented and is discussed in terms of electron-counting theories. The analogous reaction with µ4-Si[Co2(C0)7h gave indication of novel cluster products. These included [Co5Si(C0)16r, [Co9Si(C0h2r and [Co7Si(COh1L as well as the previously reported [Co9Si(CO)iif. Reactions with [Fe2(CO)sf, [HFe(C0)4r, [Fe(C0)3(NO)L [Mn(CO)sr and [Mo(C0)3(ri5-CsHs)r were less straight-forward, but again led to the detection of new clusters. ESMS analysis confirmed the unusual result that [Co14N3(C0h6]3 • is the only highnuclearity thermolysis product of [Co6N(C0)15r. The specificity of the reaction can only be established by ESMS since the technique precludes the existence of any other significant ionic products. The reaction between PCls and [Co(C0)4r gave the known [CoJ>(CO)i6r and [Co9P(C0)21f- clusters while the analogous reaction with AsCh produced three novel cobalt arsenido species, [Co~s(C0)16L [Co1As2(C0)17r and [Co9As2(C0)21r. The previously reported [Co4Sb2(C0)11r and novel [CosSb2(C0)14r clusters were identified in the reaction between SbCh and [Co(C0)4]. The synthesis and characterisation of a series of Co4(1-4-ER)2(C0)11 clusters are described. The dimethylamino functionalised examples, Co4(1-4-ECi#4NMe2)2(C0)11 E = Si, Ge, were characterised by ESMS as their [M+Ht ions. The Co4(J.4-SiR)2(C0)11 [R = Ph, CJliOMe, (CH2)30Me] clusters underwent facile substitution with isonitrile and phosphite reagents but equivalent phosphine-substituted products were not observed by ESMS. Isonitrile-substituted clusters (n > 2) gave clear~ ions in their ES mass spectra arising from in situ oxidation. The novel Co4(1-4-SiC~OMe)2(C0)1(XyNC)4 cluster was structurally characterised (below). Linked clusters of the form [Co4(1-4- SiCJliR)(C0)11Si]2X [R = H, OMe; X = (CH2)s, CJii] were isolated, albeit in very low yield. An oligomeric -[XSiCo4(C0)11 Si]-0 species was tentatively identified. A new structural isomer of [CoFe3(C0)13r was characterised. The ligand arrangement for [NE4][CoFe3(C0)13] differs significantly from that of [PPN][C0Fe3(C0)13] and [NE4][C0Ru3(C0)13]. A structure determination of [PPN][Mo(C0)3(ri5-CsHs)] is also reported.
Type of thesis
Evans, C. (2002). Electrospray mass spectrometric analysis of transition metal carbonyl clusters (Thesis, Doctor of Philosophy (PhD)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/12766
The University of Waikato
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