title: Charge Effects in PCP Pincer Complexes of Ni(II) bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis.
abstract: This contribution reports on a new family of Ni(II) pincer complexes featuring phosphinite and functional imidazolyl arms. The proligands (R) PIMC(H) OP(R') react at room temperature with Ni(II) precursors to give the corresponding complexes [((R) PIMCOP(R') )NiBr], where (R) PIMCOP(R) =κ(P) ,κ(C) ,κ(P) -{2-(R'2 PO),6-(R2 PC3 H2 N2 )C6 H3 }, R=iPr, R'=iPr (3 b, 84 %) or Ph (3 c, 45 %). Selective N-methylation of the imidazole imine moiety in 3 b by MeOTf (OTf=OSO2 CF3 ) gave the corresponding imidazoliophosphine [((iPr) PIMIOCOP(iPr) )NiBr][OTf], 4 b, in 89 % yield ((iPr) PIMIOCOP(iPr) =κ(P) ,κ(C) ,κ(P) -{2-(iPr2 PO),6-(iPr2 PC4 H5 N2 )C6 H3 }). Treating 4 b with NaOEt led to the NHC derivative [(NHCCOP(iPr) )NiBr], 5 b, in 47 % yield (NHCCOP(iPr) =κ(P) ,κ(C) ,κ(C) -{2-(iPr2 PO),6-(C4 H5 N2 )C6 H3 )}). The bromo derivatives 3-5 were then treated with AgOTf in acetonitrile to give the corresponding cationic species [((R) PIMCOP(R) )Ni(MeCN)][OTf] [R=Ph, 6 a (89 %) or iPr, 6 b (90 %)], [((R) PIMIOCOP(R) )Ni(MeCN)][OTf]2 [R=Ph, 7 a (79 %) or iPr, 7 b (88 %)], and [(NHCCOP(R) )Ni(MeCN)][OTf] [R=Ph, 8 a (85 %) or iPr, 8 b (84 %)]. All new complexes have been characterized by NMR and IR spectroscopy, whereas 3 b, 3 c, 5 b, 6 b, and 8 a were also subjected to X-ray diffraction studies. The acetonitrile adducts 6-8 were further studied by using various theoretical analysis tools. In the presence of excess nitrile and amine, the cationic acetonitrile adducts 6-8 catalyze hydroamination of nitriles to give unsymmetrical amidines with catalytic turnover numbers of up to 95.
authors.affiliation: Département de chimie, Université de Montréal, Montréal (Québec), H3C 3J7 (Canada).
authors.forename: Boris
authors.initials: B
authors.lastname: Vabre
authors.affiliation: Laboratoire de Chimie de Coordination (LCC), CNRS, 205 Route de Narbonne, 31077 Toulouse (France). yves.canac@lcc-toulouse.fr.|Université de Toulouse, UPS, INP, LCC, 31077 Toulouse (France). yves.canac@lcc-toulouse.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Canac
authors.affiliation: Laboratoire de Chimie de Coordination (LCC), CNRS, 205 Route de Narbonne, 31077 Toulouse (France). christine.lepetit@lcc-toulouse.fr.|Université de Toulouse, UPS, INP, LCC, 31077 Toulouse (France). christine.lepetit@lcc-toulouse.fr.
authors.forename: Christine
authors.initials: C
authors.lastname: Lepetit
authors.affiliation: Laboratoire de Chimie de Coordination (LCC), CNRS, 205 Route de Narbonne, 31077 Toulouse (France).|Université de Toulouse, UPS, INP, LCC, 31077 Toulouse (France).
authors.forename: Carine
authors.initials: C
authors.lastname: Duhayon
authors.affiliation: Laboratoire de Chimie de Coordination (LCC), CNRS, 205 Route de Narbonne, 31077 Toulouse (France). chauvin@lcc-toulouse.fr.|Université de Toulouse, UPS, INP, LCC, 31077 Toulouse (France). chauvin@lcc-toulouse.fr.
authors.forename: Remi
authors.initials: R
authors.lastname: Chauvin
authors.affiliation: Département de chimie, Université de Montréal, Montréal (Québec), H3C 3J7 (Canada). zargarian.davit@umontreal.ca.
authors.forename: Davit
authors.initials: D
authors.lastname: Zargarian
keywords: Fukui indices; electron localization function; hydroamination; nickel; pincer complexes