Trinuclear and Larger Clusters

The cluster [Fe20s(C0)i2] undergoes dissociative reactions with PPh3 etc. and the substituent appears at the Os atom. Nevertheless, it is argued that CO dissociates from an Fe atom since the rate parameters are closer to those for [Fe3(CO)i2] than for [Os3(CO)i2]. Reactions of [Os3(CO)n(NCMe)] and [Os3(CO)io(NCMe)2] with H2 in 1,2-dichloroethane proceed by rate-determining dissociation of the labile MeCN ligands to form [(/i-H)(H)Os3(CO)n] and [(/i-H)20s3(CO)io], respectively. Relative rates of attack on the [Os3(CO)n] inter- 

C and O atoms are bonded to the Ru atom that has lost the CO. Addition of H2 to this intermediate leads to decoordination of the O atom without much change in volume, and a similarly small volume change occurs when H2 is lost from the product and the O recoordinates. The value of A V for loss of H2 is therefore normal. Some interesting reactions of the analogous [Ru3(CO)9(/a-H)3(/x,3-CSR)] cluster with alkynes, and isomerization and reactions with H2 of the products, have been described.  

The clusters [Fe Ru4 (CO)n(/i,4-PPh)2] add two CO ligands reversibly over 30-60 min at room temperature under 1 atm CO when n = 1-3, but not when n = Addition is irreversible when n = 0. The product contains two /x3-PPh and only two M—M bonds. Substitution with (p-tolyl)NC goes by addition of the nucleophile followed by CO dissociation, but P-donors do not show formation of the intermediate adduct. 

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Trinuclear and Larger Clusters - Addition of sodium sulfide to [Cp M(MeCN)3] yields sulfido-capped [Cp 3M3(p -S)2l (M=Rh,Ir), the iridium complex also being isolated from... 

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