Reactivity of Coordinatively Unsaturated Bis(N-heterocyclic carbene) Pt(II) Complexes toward H2. Crystal Structure of a 14-Electron Pt(II) Hydride Complex
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- 作者：Orestes Rivada-Wheelaghan ; Marta Rosell贸-Merino ; Manuel A. Ortu帽o ; Pietro Vidossich ; Enrique Guti茅rrez-Puebla ; Agust铆 Lled贸s ; Salvador Conejero
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：April 21, 2014
- 年：2014
- 卷：53
- 期：8
- 页码：4257-4268
- 全文大小：617K
- 年卷期：v.53,no.8(April 21, 2014)
- ISSN：1520-510X
文摘
The reactivity toward H2 of coordinatively unsaturated Pt(II) complexes, stabilized by N-heterocyclic carbene (NHC) ligands, is herein analyzed. The cationic platinum complexes [Pt(NHC鈥?(NHC)]+ (where NHC鈥?stands for a cyclometalated NHC ligand) react very fast with H2 at room temperature, leading to hydrogenolysis of the Pt鈥揅H2 bond and concomitant formation of hydride derivatives [PtH(NHC)2]+ or hydrido鈥揹ihydrogen complexes [PtH(H2)(NHC)2]+. The latter species release H2 when these compounds are subjected to vacuum. The X-ray structure of complex [PtH(IPr)2][SbF6] revealed its unsaturated nature, exhibiting a true T-shaped structure without stabilization by agostic interactions. Density functional theory calculations indicate that the binding and reaction of H2 in complexes [PtH(H2)(NHC)2]+ is more favored for derivatives bearing aryl-substituted NHCs (IPr, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene and IMes = 1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene) than for those containing tert-butyl groups (ItBu). This outcome is related to the higher close-range steric effects of the ItBu ligands. Accordingly, H/D exchange reactions between hydrides [PtH(NHC)2]+ and D2 take place considerably faster for IPr and IMes* derivatives than for ItBu ones. The reaction mechanisms for both H2 addition and H/D exchange processes depend on the nature of the NHC ligand, operating through oxidative addition transition states in the case of IPr and IMes* or by a 蟽-complex assisted-metathesis mechanism in the case of ItBu.