Synthesis and characterization of the cluster complexes containing tetrahedral FeCrCo(μ3-S) cluster cores generated by isolobal displacement reactions. Crystal structures of (η5-RC5H4)FeCrCo(μ3-S)(CO)8 (R=H, CO2Et) and FeCo2(μ3-S)2(CO)9

The monoanions (η5-RC5H4)(CO)3Cr− (1, R=H; 2, R=Me; 3, R=CO2Et) reacted with tetrahedral cluster FeCo2(μ3-S)(CO)9 to give single isolobal displacement products (η5-RC5H4)FeCrCo(μ3-S)(CO)8 (4, R=H; 5, R=Me; 6, R=CO2Et) in 86–89% yields, whereas monoanion (η5-RC5H4)(CO)3Cr− (7, R=C(O)Me) reacted with FeCo2(μ3-S)(CO)9 to afford the expected single isolobal displacement product (η5-RC5H4)FeCrCo(μ3-S)(CO)8 (8, R=C(O)Me) in 5% yield and an unexpected square pyramidal cluster FeCo2(μ3-S)2(CO)9 (9) in 45% yield. Similarly, the dianions [η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5][(CO)3Cr−]2 (10, n=1; 11, n=2; 12, n=3) reacted with two molecules of FeCo2(μ3-S)(CO)9 to produce double isolobal displacement products [η5-C5H4CH2(CH2OCH2)nCH2C5H4-η5][FeCrCo(μ3-S)(CO)8]2 (13, n=1; 14, n=2; 15, n=3) in 32–36% yields, while treatment of dianion [η5-C5H4C(O)CH2]2[(CO)3Cr−]2 (16) with two molecules of FeCo2(μ3-S)(CO)9 gave the unexpected square pyramidal cluster FeCo2(μ3-S)2(CO)9 (9) in 42% yield and the corresponding double isolobal displacement product [η5-C5H4C(O)CH2]2[FeCrCo(μ3-S)(CO)8]2 (17) in 8% yield. Products 4–6, 8, 9, 13–15 and 17 were characterized by elemental analyses, IR and 1H NMR spectroscopy, as well as for 4, 6 and 9 by X-ray diffraction techniques.