Abstract
The research presented in this thesis is concerned with the development of routes to the synthesis of novel mixed-metal compounds of the platinum group, in particular, platinum/rhodium and platinum/gold species. Two main directions were taken in this investigation, s-alkyne complexes and cluster chemistry. The thesis is divided into two parts accordingly.
Part I
The first direction was the use of asymmetrically protected alkyne ligands
to develop mixed-metal compounds. The first chapter introduces the chemistry
of both cis- and trans- transition metal s-alkyne complexes. The synthesis
of these compounds is reviewed with specific references to Pt, Pd, Rh and
Au complexes. The wide range of industrial applications of transition metal
alkyne complexes is discussed in the context of their physical properties.
The second chapter reports the synthesis of trans-platinum complexes with
asymmetrically protected alkynes. The synthesis and characterization of the
linear complexes trans-[Pt(PnBu3)2(CC-C6H4-CC-SiiPr3)2] (1) and trans-[Pt(PnBu3)2(CC-C6H4-CC-H)2]
(2) is reported along with the crystal structure of complex (1). Complex (2)
was then used to synthesize the mixed-metal compound trans-[Pt(PnBu3)2(CC-C6H4-CC-AuPPh3)2]
(3) which was characterized both spectroscopically and by elemental analysis.
The gold(I) complex of the H-CC-C6H4-CC-SiiPr3 ligand, [Au(PPh3)(CC-C6H4-CC-SiiPr3)]
(4) was also synthesized and fully characterized. The crystal structure of
complex (4) is also reported.
(3)
The third chapter reports the synthesis and characterization of a range of
Pt(II) and Pt(IV) cis-s-alkyne complexes containing the 4,4’-bis(tert-butyl)-2,2’bipyridine.
The Pt(II) complexes [Pt(tBu2Bipy)(C=C-R)2] (6a,b,c,d) and the Pt(IV) complexes
[PtI2(tBu2Bipy)(C=C-R)2] (7a,b,c,d) are reported. (a, R= C6H5; b, R=SiMe3;
c, R=4-NO2C6H4; d, R=4-MeOC6H4). The platinum(IV) complexes are formed from
the oxidative addition of iodine to the platinum(II) cis-s-alkyne complexes
in solution. The crystal structure of [PtI2(tBu2bipy)(CCC6H4NO2)2]•0.5CHCl3
(7c) is given. The reactions of the [cis-Pt(4,4’-bis(tert-butyl)-2,2’bipyridine)dichloride]
complex with 1,2-diethynylbenzene ligands is also discussed.
Part II
The second direction investigated was the use of platinum cluster compounds
to synthesize platinum rich mixed-metal species. The fourth chapter introduces
the field of transition metal cluster chemistry, with particular reference
to the synthesis of platinum clusters and platinum/rhodium mixed metal clusters.
The relevance of transition metal clusters in catalysis is then discussed.
The fifth chapter reports the results of reactivity studies carried out on
the platinum clusters [Pt3(m-CO)3(CO)3]n2- (n=3, 4, 5) and [Pt3(m-CO)3(PCy3)3]
with the rhodium organometallic fragments [RhCp*(MeCN)3]2+ and [Rh(COD)(solv)2]+.
The majority of this section was unsucessful. The clusters and rhodium complexes
above do not appear to be viable starting materials for the synthesis of mixed-metal
clusters. The serendipitous synthesis, and subsequent spectroscopic and crystallographic
characterization of [Pt3Tl(m-CO)3(PCy3)3](PF6) (8) is reported. This complex
is known, although the published crystal structure contains a different counterion
to the structure reported herein. The crystal structure of [Rh(COD)(MeCN)2](PF6)
is also reported.
The final chapter reports the synthetic methods used for the experimetal work
in Parts I and II.