From Chromium–Chromium Quintuple Bonds to Molecular Squares and Porous Coordination Polymers

Reaction of the quintuply bonded
chromium­(I) dimer [ApCrCrAp] (Ap = sterically demanding 2-aminopyridinate)
with pyrazine yields a chromium­(II) complex with a η4:η4 face-on coordinated pyrazine dianion. Reaction
with 4,4′-bipyridine, on the other hand, completely cleaves
the metal–metal bond, leading to a chromium­(II)-based molecular
square. XRD and magnetic measurements show ligand radical anions and
a ferrimagnetic alignment of alternating metal and ligand magnetic
moments. Controlled polymerization of the molecular square with pyrazine
yields a porous coordination polymer featuring both reduced and nonreduced
linkers.

五重键合的铬（I）二聚体[ApCrCrAp]（Ap代表位阻性强的2-氨基吡啶鎓离子）与吡嗪反应，生成一种具有η4:η4面对面配位的吡嗪二阴离子的铬（II）络合物。另一方面，与4,4'-联吡啶的反应则完全断裂金属-金属键，导致形成基于铬（II）的分子方形结构。X射线衍射和磁性能量测量揭示了配体自由基阴离子以及交替金属和配体磁矩的铁磁性排列。以吡嗪为控制剂对分子方形进行聚合，得到一种具有还原和非还原键合剂的介孔配位聚合物。