The structure, preparation, and spectroscopy of a W-2(II, II) paddlewheel complex with four formamidinate ligands is reported. Upon exposure to air and moisture in solution, the W2(II, II) core undergoes an oxidative addition reaction to form a W2(III, III) edge-sharing bioctahedral (ESBO) complex with two bridging hydroxides. The products, W-2(mu-DCPF)(4) (1) and W-2(mu-OH)(2)(mu-DCPF)(2)(eta(2)-DCPF)(2) (2) where DCPF is [(3,5-Cl2C6H3)NC(H)N(3,5-Cl2C6H3)(-)], were characterized by UV-vis and H-1 NMR spectroscopy. Structural data are presented for W-2(mu-DCPF)(4) with four bridging formamidinate ligands and W-2(mu-OH)(2)(mu-DCPF)(2)(eta(2)-DCPF)(2) with the formamidinate ligands in both chelating and bridging positions. Crystallographic data for W-2(mu-DCPF)4 (1) and W-2(mu-OH)(2)(mu-DCPF)(2)(eta(2)-DCPF)(2) (2) are as follows: (1), C68H60Cl16N8O4W2, a =12.6906(3) Angstrom, b = 12.7818(4) Angstrom, c = 13.0450(3) Angstrom, alpha=109.173(1)degrees, beta = 93.865(1)degrees, gamma = 103.746(1)degrees, triclinic, P (1) over bar (No. 2), and Z = 1 and (2), C59H35Cl16N8O2W2, a=17.1524(1) Angstrom, b = 20.6568(3) Angstrom, c=19.3959(3) Angstrom, beta = 102.791(1)degrees, monoclinic, C2/c (No. 15), and Z = 4.