The reaction between [Os
3(CO)
10(NCMe)
2] and MeC
2C
2Me yields the known cluster [Os
3(CO)
9(μ-CO)(μ
3-η
2-MeC
2C
2Me)] (
1) and three previously uncharacterised products [Os
3(CO)
9(μ-CO){μ
3-η
2:μ
3-η
1:η
1:η
3-MeC
2C
2MeOC
5Me
2)Os
3(μ-CO)(CO)
9] (
2), [Os
3(CO)
9{μ
3-η
4-[(MeC
2)C
2(Me)]CO[(Me)C
2(C
2Me)]}] (
3) and [Os
3(CO)
9{μ
3-η
4-[(MeC
2)C
2(Me)]CO[(MeC
2)C
2(Me)]}] (
4). The structures of
2 and
3 have been determined by X-ray crystallography. Cluster
2 incorporates two linked triosmium clusters
joined by an unsaturated five-membered metallacycloether ring and
3 exhibits an alkyne-functionalised metallacyclohexadieneone ring.
1–
4 and [Os
3(CO)
9(μ-CO)(μ
3-η
2-PhC
2C
2Ph)] (
5) react with [Co
2(CO)
8] to form products
6–
11 in which one free alkyne function coordinates to a Co
2(CO)
6 unit in each case; the cluster [{Os
3(CO)
10}{Co
2(CO)
6}{μ
3-η
2-
![](/images/glyphs/BDL.GIF)
-(MeCC)(μ
2-η
2(CCMe)}] (
6) has been structurally characterised. The reaction of
1 and
5 with Me
3NO–MeCN leads to the replacement of one CO ligand with MeCN, the products
12 and
13 reacting with H
2O to form [Os
3(CO)
9(μ-OH)(μ
3-η
1:η
2:η
2-RC
3CHR)] (R=Me (two isomers
14,
15), Ph (
16)); the X-ray structure of
16 is reported. Reaction of
3 with Me
3NO–MeCN results in the substitution of a CO ligand with either a MeCN or NMe
3 ligand at the metallocyclic Os atom to afford the clusters [Os
3(CO)
8(L)(μ
3-η
1:η
1:η
2:η
2-{(MeC
2)C
2(Me)}
2CO)] (L=NCMe (
17), NMe
3 (
18)).