Synthesis and characterization of 1,8-naphthyridine complexes of 1.5-valent nickel

Abstract

The bidentate ligand l,8-naphthyridine (napy) reacts with nickel(I1) salts to form not only nickel(I1) complexes but also to\nform a series of dimeric complexes of the general formula [Ni,(napy),X,]Y (X = halogen, NCS, NO,; Y = PF,, B(C,H,),)\nin which the nickel has a formal oxidation number of t1.5. A single-crystal X-ray structural analysis of the complex [Ni,-\n(napy),Br,]B(C,H,), was performed on the basis of 2402 independent reflections collected by a PW 1100 diffractometer.\nThe compound crystallizes with four formula units in a monoclinic cell of symmetry P2,/c and dimensions a = 9.931 A, b =\n32.311 A, c = 16.535 A, and P = 101.5'. The structure was solved by a combination of Patterson and direct methods and\nrefined by the full-matrix least-squares method to R(F) = 0.077 and R,(n = 0.085. The structure consists of binuclear\ncations [ Ni, (napy),Br,]+ and tetraphenylborate anions B(C,H,),-. The coordination polyhedron consists of a distorted\nbicapped prism in which each nickel atom is bound to four nitrogen atoms of four napy molecules. The four nitrogen atoms\nlie in a plane about the nickel and the bromine at the apex. Each napy molecule acts as a bridge linking together two\nnickel atoms, the nickel atoms in each unit being 2.41 A apart. The magnetic and spectral electronic properties of the compounds\nare discussed. The electronic spectrum of the [Ni,(napy),Br,]B(C,H,), complex is discussed on the basis of singlecrystal\npolarized data.