Structural Studies of [Ru(1,8-naphthyridine)4]2+ and [Ru(1,5-cyclooctadiene)(1,8-naphthyridine)2]2+ as their Tetraphenylborate Salts

Abstract  

The previously reported [Ru(naph)₄]²⁺ complex (naph = 1,8-naphthyridine) has been prepared by a simplified route using [RuCl₂(1,5-COD)] _x (COD = cyclooctadiene) as starting material and isolated as its tetraphenylborate salt. The salt crystallizes in the monoclinic space group P2₁/n with a = 13.6531(3) ?, b = 12.5389(4) ?, c = 20.0349(5) ?, β = 96.5884(15)o, V = 3407.22(16) ?, D _calc = 1.300 at 150(1) K. The dication has crystallographically imposed inversion symmetry. Although the iron analogue has been found to have a coordination number of eight, the ruthenium complex is only six-coordinate, which is achieved by the presence of two monodentate and two bidentate 1,8-naphthyridine ligands. The observation of a higher coordination number for Fe(II) vs. Ru(II) can be explained by the high spin nature of the iron complex. A byproduct complex, [Ru(1,5-COD)(naph)₂][B(C₆H₅)₄]₂, could also be synthesized, isolated pure, and structurally characterized. The organometallic complex possesses an 18 electron configuration by virtue of the dicationic metal center being coordinated by the diene ligand and all four nitrogen lone pairs. This salt crystallizes in the triclinic space group textP[`1] {text{P}}bar{1} with a = 12.9538(3) ?, b = 14.9485(3) ?, c = 17.4291(3) ?, α = 69.0649(11)o, β = 78.3211(9)o, γ = 78.5629(10)o, V = 3057.50(11) ?³, D _calc = 1.293 at 150(1) K.