Dinuclear complexes of copper, silver and gold bridged by phosphoruspyridyl and phosphorusnaphthyridyl ligands.
Date
1995
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Abstract
Chapter 1 setves as an introduction to the synthesis and characterisation of copper(!), silver(!) and
gold(!) complexes of the 2,6-bis( diphenylphosphino )pyridine { (Ph2P)2py}, phenylbis(2-
pyridyl)phosphine {PhP(py)2 } and 2, 7-bis( diphenylphosphino )-4-methylnaphthyridine
{ (Ph2P)2menapy} ligands. A review of all the transition metal complexes of these ligands is
presented. Particular attention is given to the modes of coordination that these ligands may adopt
when coordinating to a transition metal.
Chapter 2 describes the reactions of the (Ph2P)2py ligand with [Cu(MeCN)4](PF 6), [Cu( Tl 2-
bipy)(MeCN)2J(PF 6), [Ag(COD)2](BF4) and [Ag(ri 2-bipy)(COD)](BF4) which result in the
formation of the dinuclear ligand-bridged complexes [Cu2{μ-(Ph2P)2py}3](PF6)
2 (1), [Cu2{μ(
P h2P)2PY }z( Tl 2 -bipy )z](PF 6)2 (2 ). [ Agz { μ -(Ph2P)2PY} 3)(BF 4)2 (3) and [ Ag2 { μ-(Ph2P)2PY} z( Tl 2 -
bipy)2](BF4 ) 2 (4) respectively. The X-ray crystal structures of 1 and 3 reveal that the three
(Ph)>)ipy ligands bridge the two metal atoms coordinating soley through their phosphorus atoms
with the result that each metal atom has a trigonal geometry. The nitrogen atoms of the pyridines
are left free resulting in a fairly open cavity in the centre of the complex cation. The cavity sizes
are calculated to be 4.9 and 5.3 A for the copper and silver complexes respectively. It is suggested
that these open cavities should be able to bind metal ions such as Cu~ and Ag+. Absorption and
emission spectra were recorded for both complexes 1 and 3 and the effects of the addition of Cu+
and Ag+ ions on the emission spectra are discussed. These studies reveal that the emission spectra
are indeed perturbed upon the addition of metal ions. The X-ray crystal structure of2 has been
detennined confirming the presence of two bridging (Ph2P)2py ligands and a 2,2'-bipyridyl ligand
chelating at each copper atom. Thus each copper atom has a tetrahedral geometry. Based on
characterisation data the structure of 4 is proposed to be similar to the structure of 2 with a
tetrahedral geometry around each silver atom.
Chapter 3 describes the reaction of the ligand PhP(py)2 with [Cu(MeCN)4](PF6),
[Ag(COD)2](BF4) and [Au(MeCN)2J(SbF6). The reaction with [Cu(MeCN)4J(PF6) afforded the
dinuclear complex [Cu2{ μ-PhP(py)2}i{MeCN)2]{PF6) 2 (5) as a crystalline solid. Single crystals
were obtained and a X-ray crystal structure revealed the first example of PhP(py)2 ·coordinating
in a bridging fashion that has been characterised in this way. The ligand coordinates to the one
copper atom through its phosphorus atom and to the other copper atom through its two nitrogen
atoms. The coordination around each copper atom is completed by an acetonitrile ligand resulting
in a tetrahedral geometry around each copper atom. The reaction of the ligand with silver(!) and
gold(I) precursors resulted in ill-defined products that could not be isolated and characterised.
Chapter 4 describes the synthesis of the novel (Ph2P)2menapy ligand and its reactions with
[Cu(MeCN)4)(PF6), [Ag(COD)2](BF4) and [Au(MeCN)2)(SbF6). The ligand proved difficult to
isolate as a pure solid and is extremely reactive towards oxygen. Reaction of the ligand with
copper(!) and silver(Q precursors afforded crystalline solids which were characterised as [Cu2{μ(
Ph?)imenapy}i(H2O)J(PFJ2 (6) and [Ag2{μ-(Ph2P)2menapy}i(H2O)4](BF4)2 (8). The structures
of these two complexes are thought to consist of the two metal atoms bridged by two
naphthyridyl ligands each bonded to the metal via the phosphorus atoms with the coordination
at each metal being completed by two water molecules. This would result in a tetrahedral
arrangement around each metal atom. To reduce the uncertainty of the proposed structures
attempts at growing single crystals of both 6 and 8 were attempted. Single crystals were obtained
in both cases but they proved to be too small for X-ray crystal structure analysis. Reaction of a
mixture of the oxidised ligand 2-diphenylphosphineoxide-7-diphenylphosphine-4-
methylnaphthyridine (Ph2POmenapyPPhi) and (Ph2P)2py resulted in the formation of a mixture
of6 and [C11z(μ-PhiPOmenapyPPhi1(MeCN)J(PF6) 2 (7). A single crystal X-ray diffraction study
has been performed on 7 which shows that the oxidised ligands bridge the two copper atoms;
coordination at the one copper is through the phosphorus atom while the ligand chelates at the
second copper via the oxygen and the adjacent naphthyridine nitrogen atom. The coordination
at each copper atom is completed by an acetonitrile ligand resulting in a tetrahedral geometry.
Reaction of the ligand with the gold(I) precursor afforded ill-defined products that could not be
isolated.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.