Synthesis and Characterization of Mononuclear and Dinuclear Manganese Bis‐acetylide Complexes

The symmetric d 5 trans ‐bis‐alkynyl complexes {Mn[(Me) 2 P(CH 2 ) n P(Me) 2 ] 2 (C≡CC 6 H 4 R) 2 } ( n = 2, R = ‐C≡CTIPS ( 2a ); n = 3, R = ‐C≡CTIPS ( 2b ); n = 2, R = F ( 4 ); n = 3; ‐C≡CTIPS) were prepared by the reaction of [Mn(dmpe) 2 Br 2 ] with two equivalents of the corresponding acetylide LiC≡CC 6 H 4 R (R = F, ‐C≡CTIPS). The reaction of compounds 2a , 2b and 4 with [Cp 2 Fe][PF 6 ] yielded the corresponding d 4 complexes {Mn[(Me) 2 P(CH 2 ) n P(Me) 2 ] 2 (C≡CC 6 H 4 R) 2 }[PF 6 ] ( n = 2, R = ‐C≡CTIPS, [ 2a ] + ; n = 3, R = ‐C≡CTIPS, [ 2b ] + ; n = 2, R = F, [ 4 ] + ; n = 3; ‐C≡CTIPS). The unsymmetrically substituted trans ‐iodo‐alkynyl complex [IMn(dmpe) 2 (C≡CC 6 H 4 ‐C≡CTIPS)] ( 5 ) was obtained by treating MeCpMn(dmpe)I with one equivalent of H‐C≡CC 6 H 4 ‐C≡CTIPS in the presenceof dmpe. Deprotection of the TIPS group with TBAF gavecomplex [IMn(dmpe) 2 (C≡CC 6 H 4 C≡CH)] ( 6 ) in 94 % yield. The neutral dinuclear complexes Mn II /Mn II compounds {[Mn((Me) 2 P(CH 2 CH 2 )P(Me) 2 ) 2 (C≡CC 6 H 4 R)] 2 (μ‐C 4 )} (R = H, Me, n ‐pentyl, F) were prepared by the direct reaction of {[Mn((Me) 2 P(CH 2 CH 2 )P(Me) 2 ) 2 I] 2 (μ‐C 4 )} with the corresponding LiC≡CC 6 H 4 R (R = H, n ‐pentyl, F). These Mn II /Mn II dinuclear compounds were further oxidized to the mixed‐valent complexes and the dicationic complexes using [Cp 2 Fe][PF 6 ]. All complexes have been characterized by NMR, IR, and Raman spectroscopy. X‐ray diffraction studies were carried out on complexes 1c , 2a , 4 , [ 4 ] + , and 6 .