Wilkinson’s manganese(I) ethylene hydride complex trans-[(dmpe)2MnH(C2H4)] (1) reacts as a source of a low-coordinate manganese(I) ethyl complex. This is illustrated in the reactivity of 1 toward a variety of reagents. Reactions of 1 with primary silanes RSiH3 (R = Ph, n Bu) at 60 °C afforded ethane and the disilyl hydride manganese complexes [(dmpe)2MnH(SiH2R)2] (4a, R = Ph; 4b, R = n Bu). Additionally, reaction with H2 at 60 °C afforded ethane and the dihydrogen hydride complex [(dmpe)2MnH(H2)] (5), which has previously been prepared by an alternate route. The proposed low-coordinate intermediate, [(dmpe)2MnEt], was not observed spectroscopically but could be trapped using isonitrile ligands; reaction of 1 with CNR (R = t Bu, o-xylyl) afforded the manganese(I) ethyl complexes [(dmpe)2MnEt(CNR)] (6a, R = t Bu; 6b, R = o-xylyl). Ethyl complex 6a did not react further with CN t Bu at 80 °C. In contrast, complex 6b reacted with excess o-xylyl isonitrile to form 1,1-insertion products, including the iminoacyl complex [(dmpe)Mn(CNXyl)3{C(NXyl)CEt(NXyl)}] (7, Xyl = o-xylyl). Complexes 4a, 6a,b, and 7, as well as the previously reported 1 and 5, have been crystallographically characterized, and DFT calculations have been employed to probe the accessibility of cis ethylene hydride and ethyl isomers of 1.