SYNTHETIC AND STRUCTURAL STUDIES ON TRANS-TETRAPYRIDINE COMPLEXES OF RUTHENIUM(II)

The complexes trans-Ru(NO2)(2)(py)(4) (1) and trans-Ru(CN)(2)(py)(4) (2) (py = pyridine) are prepared by reaction between trans-RuCl2(py)(4) in refluxing aqueous pyridine and excess NO2- or CN- respectively. The salt trans-[RuCl(py)(4)(NO)](PF6)(2) (3) is prepared from 1 by reflux in concentrated hydrochloric acid. Reaction of 3 with azide ion in acetone affords the labile intermediate trans-[RuCl(py)(4)(Me(2)CO)](+). Subsequent reaction with nitrogen ligands, L, yields the derivatives trans-[RuCl(py)(4)(L)](+) which were isolated as their PF6- salts (4, L = py; 5, L = 4-ethylpyridine, 4-Etpy; 6, L = benzonitrile, PhCN; 7, L = pyrazine, pyz; 8, L = 1-methylimidazole, 1-MeIm). The remaining chloride ligand is substituted in the presence of TIPF6 at room temperature to afford the asymmetrical derivatives trans-[Ru(py)(4)(1-MeIm)(MeCN)](PF6)(2) (10) from 8 and trans-[Ru(py)(4)(4-Etpy)(dmabn)](PF6)(2) (11, dmabn = 4-(dimethylamino)benzonitrile) from 5. The pyrazine-bridged salt [{trans-RuCl(py)(4)}(2)(mu-pyz)](PF6)(2) (9) is prepared by reaction of trans-[RuCl(py)(4)(Me(2)CO)](+) with either 1 equiv of 8 or with 1/2 equiv of pyrazine. The single-crystal X-ray structures of trans-[RuCl(py)(4)(PhCN)]PF6 (6), trans-[RuCl(py)(4)(pyz)]PF6 (7), and 9 have been determined. The salt 6, chemical formula C27H25ClF6N5PRu, crystallizes in the tetragonal space group P4nc with a = 20.191(7) Angstrom, c = 14.557(7) Angstrom, and Z = 8. 7, chemical formula C24H24ClF6N6PRu, crystalizes in the tetragonal space group P4/ncc with a = 10.7624(13) Angstrom, c = 24.615(3) Angstrom, and Z = 4. The bimetallic salt [{trans-RuCl(py)(4)}(2)(mu-pyz)](PF6)(2).2DMF (9.2DMF), chemical formula C50H58Cl2F12N12O2P2Ru2, crystallizes in the monoclinic system, space group C2/c with a = 19.0564(17) Angstrom, b = 14.664(3) Angstrom, c = 21.5112(22) Angstrom, beta = 91.877(8)degrees, and Z = 4.