Ambiphilic boryl groups in a neutral Ni() complex : a new activation mode of H
Ríos, Pablo (Universidad de Sevilla)
Borge, Javier (Universidad de Oviedo)
Fernández de Córdova Martín, Francisco José (Universidad de Sevilla)
Sciortino, Giuseppe (Universitat Autònoma de Barcelona. Departament de Química)
Lledós, Agustí (Universitat Autònoma de Barcelona. Departament de Química)
Rodríguez, Amor (Universidad de Sevilla)

Data:	2020
Resum:	The concept of metal-ligand cooperation opens new avenues for the design of catalytic systems that may offer alternative reactivity patterns to the existing ones. Investigations of this concept with ligands bearing a boron center in their skeleton established mechanistic pathways for the activation of small molecules in which the boron atom usually performs as an electrophile. Here, we show how this electrophilic behavior can be modified by the ligand trans to the boron center, evincing its ambiphilic nature. Treatment of diphosphinoboryl (PBP) nickel-methyl complex 1 with bis(catecholato)diboron (BCat) allows for the synthesis of nickel() bis-boryl complex 3 that promotes the clean and reversible heterolytic cleavage of dihydrogen leading to the formation of dihydroborate nickel complex 4. Density functional theory analysis of this reaction revealed that the heterolytic activation of H is facilitated by the cooperation of both boryl moieties and the metal atom in a concerted mechanism that involves a Ni()/Ni(0)/Ni() process. Contrary to 1, the boron atom from the PBP ligand in 3 behaves as a nucleophile, accepting a formally protic hydrogen, whereas the catecholboryl moiety acts as an electrophile, receiving the attack from the hydride-like fragment. This manifests the dramatic change in the electronic properties of a ligand by tuning the substituent trans to it and constitutes an unprecedented cooperative mechanism that involves two boryl ligands in the same molecule operating differently, one as a Lewis acid and the other one as a Lewis base, in cooperation with the metal. In addition, reactivity towards different nucleophiles such as amines or ammonia confirmed the electrophilic nature of the Bcat moiety, allowing the formation of aminoboranes. A bis(boryl)nickel complex promotes the facile and reversible activation of H through a cooperative mechanism that involves the metal and both boryl moieties in a concerted five-center process.
Ajuts:	Agencia Estatal de Investigación PID2019-109312GB-I00 Ministerio de Ciencia e Innovación RED2018-102387-T Ministerio de Economía y Competitividad CTQ2016-76267-P Agencia Estatal de Investigación CTQ2017-87889-P
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Chemical science, Vol. 12 (December 2020) , p. 2540-2548, ISSN 2041-6539

DOI: 10.1039/d0sc06014c
PMID: 34164022

9 p, 839.7 KB

El registre apareix a les col·leccions:
Articles > Articles de recerca
Articles > Articles publicats