TY - JOUR
T1 - Coordinatively unsaturated T-shaped platinum(II) complexes stabilized by small N-heterocyclic carbene ligands. synthesis and cyclometalation
AU - Roselló-Merino, Marta
AU - Rivada-Wheelaghan, Orestes
AU - Ortuno Maqueda, Manuel A
AU - Vidossich, Pietro
AU - D́ez, Josefina
AU - Lledós, Agust́
AU - Conejero, Salvador
PY - 2014/7/28
Y1 - 2014/7/28
N2 - The reaction of the N-heterocyclic carbenes (NHCs) IiPr 2Me2 and IiPr2 with [PtMe 3I]4 does not lead to the clean formation of complexes trans-[PtMeI(NHC)2], as previously found for bulkier NHCs. However, these species can be prepared in high yields by an alternative procedure using the dimethyl species [PtMe2(NHC)2] and iodomethane. The halogenated complexes trans-[PtMeI(NHC)2] have been used as precursors for the formation of the coordinatively unsaturated Pt(II) derivatives [PtMe(NHC)2][SbF6] using AgSbF6 as a halogen abstractor, whereas NaBArF is not reactive enough to completely remove the iodide ligand, leading instead to the dinuclear species [Pt2(μ-I)(Me)2(NHC)4][BArF]. Alternatively, low-coordinate T-shaped complexes [PtMe(NHC)2] [BArF] can be prepared by protonation of the dimethyl species [PtMe2(NHC)2] with [H(OEt2)2] [BArF]. The complex [PtMe(IiPr2Me 2)2][BArF] undergoes a cyclometalation process under mild heating, leading to the derivative [Pt(IiPr 2Me2′)(IiPr2Me 2)][BArF] (where the prime denotes the cyclometalated ligand). This result is in contrast with the fast cyclometalation observed for the related Pt(II) complex bearing tert-butyl-substituted NHC (ItBu). Different cyclometalation reaction mechanisms have been computationally addressed. DFT calculations indicate that the cyclometalation involving complexes with not very bulky NHCs ligands occurs via cis intermediates. Cyclometalation products bearing tert-butyl-substituted NHCs are kinetically and thermodynamically favored over those involving isopropyl groups.
AB - The reaction of the N-heterocyclic carbenes (NHCs) IiPr 2Me2 and IiPr2 with [PtMe 3I]4 does not lead to the clean formation of complexes trans-[PtMeI(NHC)2], as previously found for bulkier NHCs. However, these species can be prepared in high yields by an alternative procedure using the dimethyl species [PtMe2(NHC)2] and iodomethane. The halogenated complexes trans-[PtMeI(NHC)2] have been used as precursors for the formation of the coordinatively unsaturated Pt(II) derivatives [PtMe(NHC)2][SbF6] using AgSbF6 as a halogen abstractor, whereas NaBArF is not reactive enough to completely remove the iodide ligand, leading instead to the dinuclear species [Pt2(μ-I)(Me)2(NHC)4][BArF]. Alternatively, low-coordinate T-shaped complexes [PtMe(NHC)2] [BArF] can be prepared by protonation of the dimethyl species [PtMe2(NHC)2] with [H(OEt2)2] [BArF]. The complex [PtMe(IiPr2Me 2)2][BArF] undergoes a cyclometalation process under mild heating, leading to the derivative [Pt(IiPr 2Me2′)(IiPr2Me 2)][BArF] (where the prime denotes the cyclometalated ligand). This result is in contrast with the fast cyclometalation observed for the related Pt(II) complex bearing tert-butyl-substituted NHC (ItBu). Different cyclometalation reaction mechanisms have been computationally addressed. DFT calculations indicate that the cyclometalation involving complexes with not very bulky NHCs ligands occurs via cis intermediates. Cyclometalation products bearing tert-butyl-substituted NHCs are kinetically and thermodynamically favored over those involving isopropyl groups.
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U2 - 10.1021/om500416n
DO - 10.1021/om500416n
M3 - Article
AN - SCOPUS:84905001684
SN - 0276-7333
VL - 33
SP - 3746
EP - 3756
JO - Organometallics
JF - Organometallics
IS - 14
ER -