(C5Me5)(2)Y(mu-Ph)(2)BPh2, 1, reacted with ethyllithium at -15 degrees C to make (C5Me5)(2)Y(CH2CH3), 2, which is thermally unstable at room temperature and formed the C-H bond activation product, (C5Me5)(2)Y(mu-H)(mu-eta(1):eta(5)-CH2C5Me4)Y(C5Me5), 3, containing a metalated (C5Me5)(1-) ligand. Spectroscopic evidence for 2 was obtained at low temperature, and trapping experiments with (PrNC)-Pr-i-(NPr)-Pr-i and CO2 gave the Y-CH2CH3 insertion products, (C5Me5)(2)Y-[(PrNC)-Pr-i(Et)(NPr)-Pr-i-kappa N-2,N'], 4, and [(C5Me5)(2)Y(mu-O2CEt)](2), 5. Although 2 is highly reactive, low temperature isolation methods allowed the isolation of single crystals which revealed an 82.6(2)degrees Y-CH2-CH3 bond angle consistent with an agostic structure in the solid state. Complex 2 reacted with benzene and toluene to make (C5Me5)(2)YPh, 7, and (C5Me5)(2)YCH2Ph, 8, respectively. The reaction of 2 with [(C5Me5)(2)YCl](2) formed (C5Me5)(2)Y(mu-Cl)(mu-eta(1):eta(5)-CH2C5Me4)Y(C5Me5) in which a (C5Me5)(1-) ligand was metalated. C-H bond activation also occurred with methane which reacted with 2 to make [(C5Me5)(2)YMe](2), 9.