Ligands Based on Phosphine‐Stabilized Aluminum(I), Boron(I), and Carbon(0). Issue 12 (29th January 2019)

• Record Type: Journal Article
• Authors: Vondung, Lisa; Jerabek, Paul; Langer, Robert
• Is Part Of: Chemistry. Volume 25:Issue 12(2019)
• Page Start: 3068
• Page End: 3076
• Publication Date: 2019-01-29
• Subjects: bond theory -- computational chemistry -- ligand effects -- main group elements -- transition metals; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201805123
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A systematic quantum chemical study of the bonding in d 6 ‐transition‐metal complexes, containing phosphine‐stabilized, main‐group‐element fragments, (R3 P)2 E, as ligands (E=AlH, BH, CH +, C), is reported. By using energy decomposition analysis, it is demonstrated that a strong M−E bond is accompanied by weak P−E bonds, and vice versa. Although the Al−M bond is, for example, found to be very strong, the weak Al−P bond suggests that the corresponding metal complexes will not be stable towards phosphine dissociation. The interaction energies for the boron(I)‐based ligand are lower, but still higher than those for two‐carbon‐based ligands. For neutral ligands, electrostatic interactions are the dominating contributions to metal–ligand bonding, whereas for the cationic ligand a significant destabilization, with weak orbital and even weaker electrostatic metal–ligand interactions, is observed. Finally, for iron(II) complexes, it is demonstrated that different reactivity patterns are expected for the four donor groups: the experimentally observed reversible E−H reductive elimination of the borylene‐based ligand (E=BH) exhibits significantly higher barriers for the protonated carbodiphosphorane (CDP) ligand (E=CH) and would proceed through different intermediates and transition states. For aluminum, such reaction pathways are not feasible (E=AlH). Moreover, it is demonstrated that the metal hydrido complexes with CDP ligands might not be stable towards reduction and isomerization to a protonated CDP ligand and a reduced metal center. Abstract : Bonding fragments : Various d 6 ‐metal complexes containing phosphine‐stabilized main‐group fragments (E; see figure) as ligands are analyzed by means of quantum chemical methods, which indicate distinct differences in stability, reactivity, and metal–ligand bonding.