Darstellung,Eigenschaften und Molekülstrukturen von Komplexen des versteiften dreizähnigen Chelatliganden N,N′-Bis(diphenylphosphino)-2, 6-diaminopyridin mit MII - und M0-Übergangsmetallen [MII = Ni,Pd, Pt; M0 = Cr,Mo, W]

Preparation, Properties, and Molecular Structures of a Rigid Tridentate Chelate Ligand N, N′-Bis(diphenylphosphino)-2, 6-diaminopyridine with M^II and M⁰ Transition Metals M^II = Ni, Pd, Pt; M⁰ = Cr, Mo, W] The reaction of chlorophenylphosphane and 2, 6-Diaminopyridine give N, N′-Bis-(diphenylphosphino)-2, 6-diaminopyridine (PNP). Two types of complexes M(PNP)Cl]Cl · L (M = Ni, L = H₂O; M = Pd, L = C₂H₅OH; M = Pt) and mer-M(PNP)(CO)₃] · 2 THF (M = Cr, Mo, W) have been prepared using PNP. These coordination compounds have been characterized by means of i.r., u.v., ³¹P and ¹H n.m.r. measurements. The determination of the molecular structure of the two triclinic substances mer-Mo(PNP)(CO)₃] · 2 THF and Ni(PNP)Cl]Cl · H₂O show that the octahedral Mo(d⁶) and the square planar nickel (d⁸) compounds contain a nearly planar tridentate chelate ring system (two fused five-membered rings of the type ) in which the observed bond distances are in accordance with a π electron delocalization effect. The observed gram susceptibility of the diamagnetic Ni(d⁸) compound remains unchanged between 293 and 410 K. The relative activation property for a homogenous catalytic standard hydrogenation reaction of styrene to ethylbenzene decreases in series of catalysts of type M(PNP)Cl]Cl · L with M^II = Ni > Pd > Pt.