Cationic Re(V) oxo compounds of the type [ReO(OSiMe3)(eta (2)-B(Pz)(4)) (L)(2)]X [X = Cl, L = 4-(NMe2)C5H4N (1), 1-Meimz (1-methylimidazole; 2), 1/2 dmpe (1,2-bis(dimethylphosphino)ethane; 3), py (4a); X = I, L = py (4b)] can be prepared by reacting trans-[ReO2(eta (2)-B(pz)(4))(L)(2)] With XSiMe3. In solution, cations 1-4 are reactive species, and those with unidentate nitrogen donor ligands (1, 2, and 4) rearrange into the neutral derivatives [Reo(Cl)(oSiMe(3))(eta (2)-B(pz)(4))(L)] [L = py (5), 4-(NMe2)C5H4N (6), 1-Meimz (7)], which are also reported herein. Compounds 1-3 and 5-7 have been fully characterized by the usual spectroscopic techniques, which in some cases includes X-ray crystallographic analysis (3, 6, and 7). Compound 3 crystallizes from CH2Cl2/n-hexane as yellow crystals with one molecule of CH2Cl2 solvent, and compounds 6 and 7 crystallize from THF/n-hexane as violet and red crystals, respectively, with one molecule of THF solvent in the case of 6. Crystallographic data: 3, orthorhombic space group Pn2(1)a, a = 11.311(2) Angstrom, b = 19.135(2) Angstrom, c = 15.443(2) Angstrom, V = 3342.4(8) Angstrom (3), Z = 4; 6, triclinic space group P (1) over bar, a = 8.7179(11) Angstrom, b = 12.5724(8) Angstrom, c = 17.750(2) Angstrom, alpha = 70.454(7)degrees beta = 77.935(9)degrees, gamma = 77.129(8)degrees, V = 1768.1(3) Angstrom (3), Z = 2; 7, monoclinic space group P2(1)/c, a 16,356(2) Angstrom, b = 20.384(3) Angstrom, c = 17.360(3) Angstrom, beta = 106.971(12)degrees, V= 5535.8(14) Angstrom (3), Z = 8.