Solvent-mediated ion exchange and structural transformations of cluster-based coordination polymers

Reactions between [Nb6Cl12(CN)(6)](4-) and [Mn(salen)](+) in MeOH/H2O solvent mixture led to the formation of {[Mn(salen)(H2O)](2)[(Mn(salen))(2)(Nb6Cl12(CN)(6))])center dot 0.66 MeOH center dot 5.33H(2)O (1) which has a 2D anionic 4,4'-network built of [Nb6Cl12(CN)(6)](4-) and [Mn(salen)](+) nodes linked by CN ligands. The layers in 1 stack perfectly on top of each other and generate channels where dimeric complexes [Mn(salen)(H2O)](2)(2+) are located. Unusual cation-induced solvent-mediated structural transformations have been observed when 1 was exposed to solutions of different cations. In contact with (Me4N)Cl in MeOH, 1 is transformed to the 2D framework of the previously reported compound [Me4N](2)[(Mn(salen))(2)-(Nb6Cl12(CN)(6))] (2). In the presence of (Et(3)BzN)(+), 1 is transformed into a mixture of [Et(3)BzN](2)[(Mn(salen)(MeOH))(2)-(Nb6Cl12(CN)(6))]center dot 4MeOH (3) and [Et(3)BzN](2)[(Mn(salen))(2)-(Nb6Cl12(CN)(6))]center dot 3H(2)O (4) which are formed as crystals suitable for single-crystal X-ray diffraction. Compound 3 consists of heterotrimeric supramolecular anions built of [Nb6Cl12(CN)(6)](4-) linked to two [Mn(salen)(H2O)](+) through two CN ligands located in axial positions, while 4 features 2D anionic 4,4'-net with the same connectivity as that observed for 1 and 2 but different layer stacking and interlayer spacing. In contact with methanolic solution of (Et4N)(+), 1 is converted to [Et4N](2)[(Mn(salen)(H2O))(2)(Nb6Cl12(CN)(6))]center dot H2O (5) which is built of heterotrimeric structural motif similar to those found in 3. In the presence of M+ [M+ = Li+, Na+, K+, (Bu4N)(+), or (PPh4)(+)] the 2D framework of 1 is transformed to heteropentamers built of [Nb6Cl12(CN)(6)](4-) linked to four [Mn(salen)(MeOH)](+): [(Mn(salen)(MeOH))(4)(Nb6Cl12(CN)(6))](4) MeOH (6). The mechanism for these unusual solvent-mediated phase-to-phase transformation is discussed.