Orientational Self-Sorting in Octahedral Palladium Cages: Scope and Limitations of the " cis Rule".

Octahedral coordination cages of the general formula [Pd 6 L 12 ](BF 4 ) 12 were obtained by combining [Pd(CH 3 CN) 4 ](BF 4 ) 2 with heteroditopic N-donor ligands. Four different ligands were employed. These ligands have 3-pyridyl donor groups at one end and 4-pyridyl, imidazolyl, or triazolyl donor groups at the other end. According to a geometric analysis, cages with a cis configuration at the six metal centers should be preferred (" cis rule"). This prediction was corroborated by spectroscopic data and crystallographic analyses. Limitations of the " cis rule" were also encountered, and possible explanations are discussed.