VERSATILE ROUTES TO MONO- AND BIS(ALKYNYL) MANGANESE(II) AND MANGANESE(III) COMPLEXES VIA MANGANOCENES

With the manganocenes (RC5H4)2Mn (R = H, Me) as starting materials, paramagnetic d5 half-sandwich complexes (RC5H4)Mn(dmpe)(C⋮CR‘) (dmpe = 1,2-bis(dimethylphosphino)ethane; R = Me, R‘ = Ph, 1a; R = Me, R‘ = SiMe3, 2a; R = H, R‘ = Ph, 1b; R = H, R‘ = SiMe3, 2b) have been prepared by the reaction with terminal or SnMe3-substituted acetylenes and dmpe. The derivatives 1a and 2a could be isolated, while 1b and 2b have been identified in mixtures with the bis(dmpe)bis(acetylide)manganese species 3 (R‘ = Ph) and 4 (R‘ = SiMe3). The latter compounds are obtained as the sole products, when the manganocenes are reacted with dmpe and the corresponding acetylenes in a 1:2:2 ratio. 1a and 2a can be reversibly oxidized to the corresponding cationic Mn(III) complexes [(MeC5H4)Mn(dmpe)(C⋮CR‘)][BF4] (R‘ = Ph, [1a]+; R‘ = SiMe3, [2b]+). Compounds 1a and 2a act as scavengers of H• radicals in the 1:1:1 reaction mixtures or in the presence of n-Bu3SnH or (C5Me5)Mo(CO)3H, forming the vinylidene species (MeC5H4)Mn(dmpe)(CC(H)...