Hydrocarbon solutions of Mo-2(NMe(2))(6) and 2,2’-methylenebis(6-tert-butyl-4-methylphenol) (greater than or equal to 2 equiv), HO-CH2-OH, yield Mo-2(NMe(2))(2)(O-CH2-O)(2), I, which exists in bridged Ib and chelated Ic isomers. These are formed under kinetic control, and recrystallization allows the separation of Ib (orange cubes) from Ic (yellow cubes) both of which have been crystallographically characterized. In each there is an ethane-like O2NMo=MoO2N core with Mo-Mo = 2.2 Angstrom (average). In Ib the two O-CH2-O ligands span the Mo=Mo bond yielding a molecule of C-2 symmetry. In Ic the molecule has near-C-2 symmetry in the solid state, but in solution there is either rapid rotation about the M=M bond or the anti-rotamer is preferred. In benzene-d(6), Ib and Ic do not interconvert at 110 degrees C over a period of days. However, the addition of pyridine or acetonitrile causes the isomerization of Tt, to Ic, thereby establishing that Ic is the thermodynamic isomer. The rate of conversion of Ib to Ic has been shown to be dependent on the square of the concentration of added pyridine : k(obs) = k[py](2). From the temperature dependence of k(obs), we determine Delta H-double dagger = 19 (+/-1) kcaymol and Delta S-double dagger = -25 (+/-3) eu for the pyridine-promoted isomerization of Ib to Ic. The related reaction involving W-2(NMe(2))(6) and HO-CH2-OH (greater than or equal to 2 equiv) in hydrocarbon solvents at room temperature and below yields a dark brown crystalline compound, wherein C-H activation has occurred at one of the O-CH2-O diolate ligands, W-2(mu-H)(mu-NMe(2))(NMe(2))(eta(2)-O-CH2-O)(eta(3)-O-CH-O)(HNMe(2)), 2. The W-W distance in 2 is 2.495(1) Angstrom, consistent with a (W=W)(8+) core. Heating 2 in the solid-state under a dynamic vacuum leads to the elimination of HNMe(2) and the formation of 3, W-2(NMe(2))(2)(eta(2)-O-CH2-O)(2), an analog of Ic. In benzene-d(6) the equilibrium involving 2 and 3 + HNMe(2) has been observed by H-1 NMR spectroscopy. The addition of pyridine to hydrocarbon solutions of 3 yields W-2(mu-H)(mu-NMe(2))(eta(2)-O-CH2-O)(mu(3)O-CH-O)(NMe(2))(py), 4, which has been shown by single-crystal X-ray crystallography to be an analogue of 2. Studies of the addition of PMe(3) to toluene-d(8) solutions of 3 at low temperatures reveal that adduct formation occurs prior to C-H oxidative addition. For the equilibrium involving 4 and 3 + py in benzene-d(6), Delta H degrees = 14 (+/-l) kcal/mol and Delta S degrees = 22 (+/-3) eu.