[(dmpe)₂MnH(C₂H₄)] as a Source of a Low-Coordinate Ethyl Manganese(I) Species: Reactions with Primary Silanes, H₂, and Isonitriles

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, ⁿBu) at 60 °C afforded ethane and the disilyl hydride manganese complexes [(dmpe)₂MnH­(SiH₂R)₂] (4a, R = Ph; 4b, R = ⁿBu). 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 = ^tBu, o-xylyl) afforded the manganese­(I) ethyl complexes [(dmpe)₂MnEt­(CNR)] (6a, R = ^tBu; 6b, R = o-xylyl). Ethyl complex 6a did not react further with CN^tBu 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.