The monoanions (η 5 -RC 5 H 4 )(CO) 3 Cr - (1, R=H; 2, R=Me; 3, R=CO 2 Et) reacted with tetrahedral cluster FeCo 2 (μ 3 -S)(CO) 9 to give single isolobal displacement products (η 5 -RC 5 H 4 )FeCrCo(μ 3 -S)(CO) 8 (4, R=H; 5, R=Me; 6, R=CO 2 Et) in 86-89% yields, whereas monoanion (η 5 -RC 5 H 4 )(CO) 3 Cr - (7, R=C(O)Me) reacted with FeCo 2 (μ 3 -S)(CO) 9 to afford the expected single isolobal displacement product (η 5 -RC 5 H 4 )FeCrCo(μ 3 -S)(CO) 8 (8, R=C(O)Me) in 5% yield and an unexpected square pyramidal cluster FeCo 2 (μ 3 -S) 2 (CO) 9 (9) in 45% yield. Similarly, the dianions [η 5 -C 5 H 4 CH 2 (CH 2 OCH 2 ) n CH 2 C 5 H 4 -η 5 ][(CO) 3 Cr - ] 2 (10, n=1; 11, n=2; 12, n=3) reacted with two molecules of FeCo 2 (μ 3 -S)(CO) 9 to produce double isolobal displacement products [η 5 -C 5 H 4 CH 2 (CH 2 OCH 2 ) n CH 2 C 5 H 4 -η 5 ][FeCrCo(μ 3 -S)(CO) 8 ] 2 (13, n=1; 14, n=2; 15, n=3) in 32-36% yields, while treatment of dianion [η 5 -C 5 H 4 C(O)CH 2 ] 2 [(CO) 3 Cr - ] 2 (16) with two molecules of FeCo 2 (μ 3 -S)(CO) 9 gave the unexpected square pyramidal cluster FeCo 2 (μ 3 -S) 2 (CO) 9 (9) in 42% yield and the corresponding double isolobal displacement product [η 5 -C 5 H 4 C(O)CH 2 ] 2 [FeCrCo(μ 3 -S)(CO) 8 ] 2 (17) in 8% yield. Products 4-6, 8, 9, 13-15 and 17 were characterized by elemental analyses, IR and 1 H NMR spectroscopy, as well as for 4, 6 and 9 by X-ray diffraction techniques.