The reduction of [((Bu3SiO)-Bu-t)(2)MOCl](2) (2(2)) provided the cyclometalated derivative, (silox)(2)HMoMo(kappa-O,C-OSi(t)Bu(2)CMe(2)Ch(2))(silox) (3), and alkylation of 2(2) with MeMgBr afforded [(tBu(3)SiO)(2)MoCH3](2) (4(2)). The hydrogenation of 4(2) was ineffective, but the reduction of 2(2) under H-2 generated [((Bu3SiO)-Bu-t)(2)MoH](2) (5(2)), and the addition of 2-butyne to 3 gave [(silox)(2)Mo](2)(mu:eta(2)eta(2)-C2Me2) (6), thereby implicating the existence of [(silox)(2)Mo](2) (1(2)). The addition of (silox)H to Mo(NMe2)(4) led to (silox)(2)Mo(NMe2)(2) (7), but further elaboration of the core proved ineffective. The silanolysis of MoCl5 afforded (silox)(2)MoCl4 (8) and (silox)(3)MoCl3 (9) as a mixture from which pure 8 could be isolated, and the addition of THF or PMe3 resulted in derivatives of 9 as (silox)(2)Cl3MoL (L = THF, 10; PMe3, 11). Reductions of 11 and (silox)(2)WCl4 (15) in the presence of excess PMe3 provided (silox)(2)Cl2MPMe3 (M = Mo, 12; W, 16) or (silox)(2)HW(eta(2)-CH2PMe2)PMe3 (14). While "(silox)(2)W(PMe3)(2)" was unstable with respect to W(N) as 14, a reduction of 12 led to the stable Mo(II) diphosphine, (silox)(2)Mo(PMe3)(2) (17). X-ray crystal structures of 10 (pseudo-O-h), 12 (square pyramidal), and 14 and 17 (distorted T-d) are reported. Calculations address the diamagnetism of 12 and 16, and the distortion of 17 and its stability to cyclometalation in contrast to 14.