Palladium N(CH2CH2P(i)Pr2)2-dialkylamides: synthesis, structural characterization, and reactivity.
Palladium(II) aminodiphosphine PNP pincer complexes [PdR(PNP(H))]PF(6) (1(R); R = Cl Me, Ph; PNP(H) = HN(CH(2)CH(2)P(i)Pr(2))(2)) were prepared. Deprotonation with KO(t)Bu affords dialkylamides [PdR(PNP)] (2(R); R = Cl Me, Ph; PNP = (NCH(2)CH(2)P(i)Pr(2))(2)) in high yield which are stable toward beta-H elimination. While AgPF(6) oxidizes the amides, cationic amido complexes [PdL(PNP)]PF(6) (3(L); L = CN(t)Bu, PMe(3)) were obtained upon chloride abstraction from 1(Cl) with TlPF(6). The reaction of amide 2(Cl) with MeOTf results in N-methylation yielding [PdCl(PNP(Me))]OTf (5) quantitatively. N-H acidities of the amino complexes 1(Me) (pK(a) = 24.2(1)) and 1(Ph) (pK(a) = 23.2(1)) were determined in dmso. Complexes 1(Cl), 1(Me), 2(Cl) 2(Me), 3(CNtBu), and 5 were structurally characterized by single crystal X-ray diffraction. The amido complexes feature pyramidal nitrogen atoms in the solid state. The molecular structures, high N-basicity, and reactivity of the amido complexes can be explained with Pd-N(amido) bonding that is characterized by strong N-->Pd sigma-donation and repulsive d(pi)-p(pi) pi-interactions. This interpretation was confirmed by density functional theory (DFT) calculations of 2(Cl).
Marziale
Alexander N
AN
Technische Universität München, Department Chemie, Lichtenbergstrasse 4, D-85747 Garching b München, Germany.
Herdtweck
Eberhardt
E
Eppinger
Jörg
J
Schneider
Sven
S
D000577:Amides / Q000737:chemistry*; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*
D000577:Amides; D009942:Organometallic Compounds; D010720:Phosphines; D010165:Palladium