| Summary: | Previous studies of the ligand properties of primary, secondary and tertiary phosphines on metal monomers have been carried out. These studies investigated the properties of the phosphines in terms of the effects of their basicity and Tolman's cone angle on the metal substrate. The reactions of [Os<SUB>3</SUB>(CO)<SUB>10</SUB>(MeCN)<SUB>2</SUB>] with a series of primary, secondary and tertiary phosphines (PR<SUB>x</SUB>H<SUB>3-x</SUB>) where R = Me, Et, i-Pr, Ph, were studied by variable temperature <SUP>31</SUP>P{<SUP>1</SUP>H}, and <SUP>31</SUP>P nmr. The reactions were monitored by nmr firstly after 24 hours at ambient temperature, the tubes were then heated to 60°C for 1 hour and the products studied by nmr, ir and mass spectroscopy. The products present included <I>mono</I> and disubstituted clusters. Also identified were inter- and intramolecular phosphinidene bridged species. The cluster bound products were initially identified on the basis of the <SUP>1</SUP>J<SUB>PH</SUB> coupling constants - approximately 400H<SUB>z</SUB> as opposed to approximately 200H<SUB>z</SUB> for the free phosphines. Stability studies were carried out on the triosmium benzene cluster system [Os<SUB>3</SUB>(CO)<SUB>9</SUB>(η<SUP>2</SUP>η<SUP>2</SUP>η<SUP>2</SUP>C<SUB>6</SUB>H<SUB>6</SUB>)]. The cluster was reacted with a series of tertiary phosphines initially with heating and later uv irradiation to attempt to displace the benzene ligand. The ligand has proven to be strongly bound to the cluster as there was no displacement observed, though CO displacement occurs affording <I>mono-, bis-</I> and <I>tris-</I>phosphine cluster derivatives. The benzene ligand attached to the cluster also proved resistant to displacement <I>via</I> high vacuum pyrolysis. Study of the mechanism for the thermal conversion of the raft cluster [Os<SUB>6</SUB>(CO)<SUB>21</SUB>] with the species [Os<SUB>6</SUB>(CO)<SUB>18</SUB>] under vacuum has been carried out <I>via </I>pressure monitoring, showing the loss of CO to be a stepwise process. During this reaction the formation of a novel ketenylidene species, [Os<SUB>3</SUB>(CO)<SUB>11</SUB>CCO] has been observed. This species has been characterised by high resolution FAB mass spectroscopy.
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