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Molecular tetrarhodium cluster complexes with facial (µ 3 -) cyclooctatetraene ligands are synthesized from [Rh 4 (CO) 12 ] 2 and 1,3,5,7-cyclooctatetraene (cot) or 1,4-(SiMe 3 ) 2 C 8 H 6 , respectively. The reactions proceed in a cooperative fashion, with all four metal atoms of the cluster being involved. Reaction of 2 with cot at low temperature (boiling n-pentane) only gives the mono-cot complex [Rh 4 (CO) 8 (µ 3 -C 8 H 8 )] 4, whereas at higher temperature (boiling n-heptane) the bis-cot cluster complex [Rh 4 (CO) 6 (µ 3 -C 8 H 8 )(η 4 -C 8 H 8 )] 5 is formed exclusively. Complex 4 is also prepared from 5 and [Fe(CO) 5 ]. From 2 and 1,4-(SiMe 3 ) 2 C 8 H 6 in boiling n-pentane only the complex [Rh 4 (CO) 6 {µ 3 -C 8 H 6 (SiMe 3 ) 2 }{η 4 -C 8 H 6 (SiMe 3 ) 2 }] 6 is obtained in quantitative yield. Substitution of the apical ligands in 4 with 1,4-(SiMe 3 ) 2 C 8 H 6 , and in 5 with 1,3-cyclohexadiene or 1,5-cyclooctadiene gives the complexes [Rh 4 (CO) 6 (µ 3 -C 8 H 8 ){η 4 -C 8 H 6 (SiMe 3 ) 2 }] 7, [Rh 4 (CO) 6 (µ 3 -C 8 H 8 )(η 4 -C 6 H 8 )] 8 and [Rh 4 (CO) 6 (µ 3 -C 8 H 8 )(η 4 -C 8 H 12 )] 9, respectively. The crystal and molecular structures of 4, 5, 6, 8 and 9 were determined. The apical C 8 H 6 R 2 ligands in 5, 6 and 7 attain the 1,2,5,6-η 4 -coordination mode through non-adjacent double bonds. DALTON