Reactivity of Hydride Bridges in High-Spin [3M–3(μ-H)] Clusters (M = Fe^II, Co^II)

Abstract

The designed [3M-3(μ-H)] clusters (M = Fe(II), Co(II)) Fe3H3L (1-H) and Co3H3L (2-H) [where L(3-) is a tris(β-diketiminate) cyclophane] were synthesized by treating the corresponding M3Br3L complexes with KBEt3H. From single-crystal X-ray analysis, the hydride ligands are sterically protected by the cyclophane ligand, and these complexes selectively react with CO2 over other unsaturated substrates (e.g., CS2, Me3SiCCH, C2H2, and CH3CN). The reaction of 1-H or 2-H with CO2 at room temperature yielded Fe3(OCHO)(H)2L (1-CO2) or Co3(OCHO)(H)2L (2-CO2), respectively, which evidence the differential reactivity of the hydride ligands within these complexes. The analogous reactions at elevated temperatures revealed a distinct difference in the reactivity pattern for 2-H as compared to 1-H; Fe3(OCHO)3L (1-3CO2) was generated from 1-H, while 2-H afforded only 2-CO2.

An iron(ii) hydride complex of a ligand with two adjacent β-diketiminate binding sites and its reactivity

“…For instance, I has been demonstrated to undergo CO 2 insertion, and recently, Murray and coworkers reported a triron(II) trihydride complex Fe 3 H 3 L [where L 3− is a tris(β-diketiminate) cyclophane] which is also able to react with CO 2 via insertion; interestingly, after insertion of the first CO 2 molecule the remaining Fe-H-Fe units showed a marked lack of reactivity. 6,15 …”

Alkene Hydrogenations by Soluble Iron Nanocluster Catalysts

“…The Fe 6 cluster is a truncated derivative of the Fe 7 cluster and bears one μ 2 ‐H and four μ 3 ‐H atoms coordinated to iron. The highly symmetrical Fe 7 cluster, a low‐valent “Fe wheel”, contains six peripheral μ 2 ‐hmds ligands and six μ 3 ‐H ligands 19. The composition of the cluster mixture was further verified by X‐ray analysis, elemental analysis, and LIFDI‐MS ( m / z 1301.2287, 1358.1793).…”

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

“…We have previously reported the synthesis and reactivity towards CO 2 of hexagonal [M 3 (µ‐H) 3 ] 3+ (M=Fe 2+ or Co 2+ ) clusters supported by a tris(β‐diketiminate) cyclophane . These complexes exhibit exceptional substrate specificity; for example, hydride insertion into CO 2 readily occurs whereas reaction with weak acids is markedly slower or unobserved.…”