Synthesis and Charactertzation of Mononuclear and Dinuclear Manganese Bis-acetylide Complexes

The symmetric d(5) trans-bis-alkynyl complexes {Mn[(Me)(2)P(CH2)(n)P(Me)(2)](2)(C CC6H4R)(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 CC6H4R (R = F, -C CTIPS). The reaction of compounds 2a, 2b and 4 with [Cp2Fe][PF6] yielded the corresponding d(4) complexes {Mn[(Me)(2)P(CH2)(n)P(Me)(2)](2)(C CC6H4R)(2)}[PF6] (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 CC6H4-C CTIPS)] (5) was obtained by treating MeCpMn(dmpe)l with one equivalent of H-C CC6H4-C CTIPS in the presence of dmpe. Deprotection of the TIPS group with TBAF gave complex [IMn(dmPe)(2)(C CC6H4-C CTIPS)] (6) in 94 % yield. The neutral dinuclear complexes Mn-II/Mn-II compounds {[Mn((Me)(2)P(CH2CH2)P(Me)(2))(2)(C CC6H4R)](2)(mu-C-4)} (R = H, Me, n-pentyl, F) were prepared by the direct reaction of {Mn((Me)(2)P(CH2CH2)P(Me)(2)l](2)(mu-C-4)} with the corresponding LiC CC6H4R (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 [Cp2Fe][PF6]. 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.