The coordination chemistry of 2,2’-dipyridyl diselenide (PySeSePy) (2) (C10H8N2Se2) has been investigated and its crystal structure has been determined (monoclinic, P2(1)/c, a = 10.129(2) Angstrom, b = 5.7332(12) Angstrom, c = 19.173(3) Angstrom, beta = 101.493(8)degrees, Z = 4). In metal complexes the ligand was found to coordinate in three different modes, as also confirmed by X-ray structure determination. N,N’-coordination was found in the zinc complex [Zn(PySeSePy)Cl-2] (3) (C10H8Cl2N2Se2Zn, triclinic, , a = 7.9430(10) Angstrom, b = 8.147(2) Angstrom, c = 11.999(2) Angstrom, alpha = 93.685(10)degrees, beta = 107.763(10)degrees, gamma = 115.440(10)degrees, Z = 2) and Se,Se’-coordination in the adduct of the ligand with bis(pentafluorophenyl)mercury(II) [PySeSePyHg(C6F5)(2)] (5) (C10H8F10HgN2Se2, monoclinic, P2(1)/n, a = 7.7325(10) Angstrom, b = 5.9974(14) Angstrom, c = 25.573, beta = 98.037(10)degrees, Z = 2), which however displays only weak interactions between selenium and mercury. The reaction of the ligand with norbornadiene carbonylcomplexes of molybdenum and tungsten leads to reductive cleavage of the selenium-selenium bond with oxidation of the metal center and concomitant addition of the resulting selenolate to the metal carbonyl fragment. Thus the 7-coordinate complexes [Mo(SePy)(2)(CO)(3)] (6) (C(13)H(8)MoN(2)O(S)e(2), monoclinic, P2(1)/n, a = 9.319(3) Angstrom, b = 12.886(5) Angstrom, c = 13.231(6) Angstrom, beta = 109.23(3)degrees, Z = 4) and [W(SePy)(2)(CO)(3)] (7) (C13H8N2O3Se2W, monoclinic, P2(1)/n, a = 9.303(2) Angstrom, b = 12.853(2) Angstrom, c = 13.232(2) Angstrom, beta = 109.270(10)degrees, Z = 4) were obtained. The same N,Se-coordination pattern emerges from the reaction of [Fe-2(CO)(9)] with (2) leading to [Fe(SePy)(2)(CO)(2)] (8) (C12H8FeN2O2Se2, monoclinic, , a = 8.6691(14) Angstrom, b = 12.443(2) degrees, c = 14.085(2) Angstrom, alpha = 105.811(10)degrees, beta = 107.533(8)degrees, gamma = 92.075(10)degrees, Z = 4).