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Synthesis of low-coordinate transition metal complexes of the heavier group 13 elements

Coombs, Natalie D. 2008. Synthesis of low-coordinate transition metal complexes of the heavier group 13 elements. PhD Thesis, Cardiff University.

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Abstract

This thesis describes the synthesis, structural and reaction chemistry of a number of novel gallium and indium containing species, including metal complexes featuring previously unreported gallium and indium ligand systems. The synthesis, spectroscopic and structural characterisation of the asymmetric haloindyl (n5-C5R5)Fe(CO)2In(Mes*)Br (R = H, Me) and halogallyl Cp*Fe(CO)2Ga(Mes)I complexes are reported herein, with Cp*Fe(CO)2ln(Mes*)Br representing the first example of structurally characterised asymmetric bromoindyl complex. Cp*Fe(CO)2In(Mes*)Br is a versatile substrate for the synthesis of asymmetric indyl complexes via substitution chemistry, thereby allowing the synthesis and characterisation of Cp*Fe(CO)2In(Mes*)ERn (ERn = OC6H4/Bu-4, SPh). The synthesis, spectroscopic and structural characterisation of the dihalogallyl complex Cp*Fe(dppe)Gal2 is also reported this synthesis was accomplished via photolytic displacement of the carbonyl ligands in Cp*Fe(CO)2Gal2 2 by dppe 1,2-bis(diphenylphosphino)ethane. Cp*Fe(dppe)Gal2 has proven to be versatile reagent in the generation of the asymmetric halogallyl species via substitution chemistry with retention of the iron-gallium bond, thereby allowing the synthesis and characterisation of Cp*Fe(dppe)Ga(Mes)I. The diiodogallyl complex has also been implicated in the synthesis of the first structurally characterised base-free cationic gallylene complex Cp*Fe(CO)2Gal + BAr/4 bearing a terminally bound Gal ligand which is valence isoelectronic with CO and N2. Investigations into the synthesis of molybdenum- and ruthenium-phosphine containing systems are also reported herein. Insertion of 'Gal' into metal-halogen bonds has proved to a viable synthetic route, for example in the 7 7 formation of (n-C7H7)Mo(CO)2Gal2 2. Further reaction of (n-C7H7)Mo(CO)2Gal2 2 with dppe, however, has been shown to yield (r - C7H7)Mo(CO)2Gai2 2(u-dppe). Investigation of 'Gal' insertion reactions involving ruthenium-halogen bonds have shown to yield the tetraiodogallate species CpRu(PPh3)2(u-I)Gal3 and CpRu(dppe) Gal4. The synthesis, spectroscopic and structural characterisation of the bridging halo-indanediyl complexes Cp*Fe(CO)2 2lnX (X = Br, I) are reported. The bromo-substituted species has proven to be a useful precursor in the synthesis of the cationic trimetallic system {Cp*Fe(CO)2}2(-In) + BA/4, the formation of which has been shown to be strongly dependant on the nature of abstracting agent and on the identity of the halide. Reactivity studies of {Cp*Fe(CO)2}2( i-E) + (E = Ga, In) involving the addition of nucleophiles has allowed the synthesis and characterisation of the three-coordinate cationic complexes {Cp*Fe(CO)2}2(u-E L) + BAr4 (E = Ga, In L = thf, 4-picoline, PPh3). The syntheses and metallation of sterically bulky carbazol-9-yl ligands derived from 1,8-diaryl-3,6-dimethylcarbazole are described herein. Furthermore, the synthesis and structural characterisation of the amidogally l complexes (1,8-diphenyl-3,6-dimethylcarbazol-9-yl)gallium dichloride and (1,8-dimesity 1-3,6-dimethylcarbazol-9-yl)gallium dichloride are reported by salt metathesis reactions involving gallium trichloride. Investigations of subsequent reduction chemistry using potassium metal yielded the potassium salt 1,8-diphenyl-3,6-dimethylcarbazol-9-yl-potassium. Quantum chemical investigations using Density Functional Theory have been explored to probe the electronic structure in the novel bond types. In particular, studies targeted factors affecting the degree of 7c back-bonding (and hence multiple bond character) within the TM-ER bond.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303213670
Date of First Compliant Deposit: 30 March 2016
Last Modified: 15 Jan 2019 16:02
URI: http://orca-mwe.cf.ac.uk/id/eprint/54759

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