SYNTHESIS OF IRON CARBONYL CLUSTERS WITH TRIGONAL-BIPYRAMIDAL E2FE3 CORES (E=GE, SI) - CRYSTAL-STRUCTURES OF (MU-3-GEET)2FE3(CO)9, [MU-3-GE(FE(CO)2CP)]2FE3(CO)9, AND [MU-3-SI(FE(CO)2CP)]2FE3(CO)9

The reaction of RGeH3 with Fe3(CO)12 at 50 °C gives low-to-moderate yields of the trigonal-bipyramidal clusters (µ3-GeR)2Fe3(CO)9 (3) together with complexes tentatively identified as (µ-GeRH)2Fe2(CO)7 and (µ-GeRH)3Fe2(CO)6. A superior route to clusters 3 is from RGeH3 and Fe(CO)5 at 140 °C. The corresponding reactions with silanes RSiH3 appear to give similar products, but the lack of stability precluded complete characterization. The stable Si2Fe3-core cluster [µ3-Si{Fe(CO)2Cp}]2Fe3(CO)9 (5a) can be prepared in good yield by reacting SiH4 with Fe(CO)5 and [Fe(CO)2Cp]2 at 150 °C; the corresponding Ge analogue 5b is similarly available from GeH4. X-ray crystal structures are reported for cluster 3 (R = Et; C13H10Fe3Ge2O9, a = 9.341 (2) Å,b = 15.264 (4) Å, c = 14.216 (3) Å, β = 91.22 (2)°, P21/n, Z = 4), for 5a (C23H10Fe5Si2O13, a = 10.020 (8) Å b = 9.914 (6) Å, c = 28.07 (2) Å, β = 92.68 (7)°, P21/n, Z = 4), and for 5b (C23H10Fe5Ge2O13, a = 10.125 (3) Å, b = 10.024 (3) Å, c = 28.308 (9) Å, β = 92.53 (3)°, P21/n, Z = 4). The E2M3 cores are slightly irregular trigonal bipyramids with Ge-Fe ranging from 2.302 to 2.336 Å and Fe-Fe = 2.721-2.742 Å in 3; in 5a, Si-Fe = 2.294-2.324 Å (distinctly longer than the external Si-Fe value of 2.251 Å) and Fe-Fe is 2.654-2.687 Å, while in 5b Ge-Fe = 2.365-2.391 Å (external Ge-Fe = 2.318 Å) and Fe-Fe = 2.717-2.742 Å. © 1990, American Chemical Society. All rights reserved.