This thesis describes the study of a series of platinum complexes, with particular
emphasis towards hydrosilation.
Platinum bis(phosphine) azodicarbonyl complexes Pt(PRI
3)2(R20CNNCOR2) (RI
= Ph, Me; R2 = Ph, Me, OEt, Pri) were synthesised and studied. Multinuclear NMR
spectroscopy on Pt(PRI3)2(R20CNNCOR2) revealed that the dicarbonyl substituted azo
ligand is co-ordinated asymmetrically, consistent with a five membered, Pt-N-N-C-O
ring. The crystal structure of Pt(PPh3)2(Pri02CNNC02Pri) shows that the co-ordination
sphere of platinum is essentially square planar and co-planar with the five-membered,
Pt(1)-0(1)-C(5)-N(2)-N(1) ring. The Pt(PRI
3)lR20CNNCOR2) complexes show
sensitivity towards chlorinated solvents (CH2CI2, CHCI3) under photolysis conditions
forming the corresponding platinum bis(phosphine) dichloride complexes; the same
products are formed in a slower thermal reaction but only for complexes with
azodicarboxylate ligands. Complexes with azodicarboxylate ligands also react
photochemically with ethylene in ds-THF yielding Pt(PPh3)2(C2H4) but the azodiacyl
analogues are inert in this respect.
Azodicarboxylate compounds R02CNNC02R (R = Et, Pri, But) are inhibitors of
the catalytic activity of [(Pt {174
_(CH2=CHSiMe2hO }h {.u-( CH2=CHSiMe2)20}] for the
hydrosilation reaction. The inhibited species can be decomposed thermally or
photoch~mically to give active hydrosilation catalysts. It was found that the bulky azo
compound But02CNNC02But was the least effective inhibitor of [(Pt{ 174
-
'(CH2=CHSiMe2hO} )2(P-( CH2=CHSiMe2)20)].
The photochemistry of platinum bis(phosphine) malonates and phthalates was
found to be limited, and their reactivities were much lower compared to the analogous
oxalate complexes.
Silyl hydride complexes, cis-Pt(PCY3)2(H)(SiR3), were synthesised from the
reaction of Pt(PCY3)2 and the corresponding silane. These complexes were undergo
dynamic exchange in solution. Two exchange processes were identified; the first involves
mutual phosphine exchange, i.e. positional interchange between the hydride and the silyl
ligands. The second process occurs at higher temperatures (above 290 K) and involves
the elimination and re-addition of the silane ligand HSiR3. Thermodynamic and activation
parameters are obtained for cis-Pt(PCY3)2(SiR3) (R = Ph, SiR3 = SiMe2CH2CH=CH2,
SiMe2Et). The reaction of Pt(PCY3)2 with the disilane HSiMe2(l,2-C6~)SiMe2H is
thought to form a Pt(IV) bis(silyl) dihydride trigonal bipyramidal species of the form,
Pt(PCY3)(H)2[SiMe2(1,2-C6~)SiMe2]' where the hydride ligands are in the axial
positions. All of the platinum silyl hydride complexes studied degrade thermally to form
trans-Pt(PCY3)2(H)2 at, or above, room temperature.