The synthesis and characterization of a novel sterically demanding selenol HSeC6H3-2,6-Mes(2), 1 (Mes = -C6H2-2,4,6-Me(3)), the corresponding diselenide, 2, and some of its metal derivatives are described. Solvated and unsolvated zinc selenolates were prepared by the treatment : of the amide Zn{N(SiMe(3))(2)}(2) in hexane with 2 equiv of the bulky selenol, 1. Crystallization from hexane produces monomeric Zn(SeC6H3-2,6-Mes(2))(2), 3, while crystallization from tetrahydrofuran results in the monomeric adduct Zn(SeC6H3-2,6-Mes(2))(2)(THF), 4. Treatment of Mn{N(SiMe(3))(2)}(2) with 2 equiv of 1 : and crystallization from methylene chloride yields Mn(SeC6H3-2,6-Mes(2))(2).2CH(2)Cl(2), 5.2CH(2)Cl(2). The synthesis and structure determination of [Mn(SeMes*)(2)THF](2).4PhMe (Mes* = -C6H2-2,4,6-t-Bu(3)), 6, were-also undertaken to compare the steric properties of the -SeC6H3-2,6-Mes(2) and -SeMes* ligands. The compounds 1-5 were characterized by IR and H-1 NMR spectroscopy,and 1-4 were also characterized by Se-77 NMR spectroscopy. The structures of 2-6 were determined by X-ray crystallography. In 3 the zinc has a crystallographically required linear coordination whereas the manganese atom in 5 has a bent geometry with a Se-Mn-Se angle of 119.9(1)degrees. In contrast, the structure of 6 is dimeric even in the presence of THF donor ligands. Crystal data with Mo K alpha (lambda = 0.710 69 Angstrom)(2 and 5) or-Cu K alpha (lambda = 1.541 78 Angstrom) (3 and 4) radiation at 130 K : 2, a = 16.144(4) Angstrom, b = 15.122(3) Angstrom, c = 16.155(4) Angstrom, beta = 91.86(2)degrees, monoclinic, Z = 4, space group P2(1)/n, R = 0.056; 3, a = 9.318(2) Angstrom, b = 10;904(4) Angstrom, c = 11.796(4) Angstrom, alpha = 62.25(2)degrees, beta = 73.76(2)degrees, gamma = 68.92(2)degrees, triclinic, Z = 2, space group P1, R = 0.059; 4, a = 10.621(3) Angstrom, b = 10.828(3) Angstrom, c = 22.491(6) Angstrom, alpha = 86;76(2)degrees, beta = 85.20(2)degrees, gamma =60.57(2)degrees triclinic, Z = 2, space group P ($) over bar 1, R = 0.073; 5.2CH(2)Cl(2), a = 20.061(5) Angstrom, b = 14.705(5) Angstrom, c = 15.781(5) Angstrom, orthorhombic, Z= 8, space group Peen, R= 0.063; 6.4PhMe, a = 19.000(8) Angstrom; b = 19.626(6) Angstrom, c = 27.687(7) Angstrom, beta = 98.18(5)degrees, Z = 4, space group P2(1)/n, R = 0.086.