Subtle ring-constraint effects on the formation of metallacycles. Cyclodimer versus cyclotrimer of bis(chloro)-1,4-bis(dimethyl-3 or 4-pyridylsilyl)benzenepalladium(II) complexes.
Stepwise modulation of the ring size of metallacyclic compounds via subtle ring-constraint effects has been established. The reactions of (COD)PdCl 2 with p- or m-psb ligand [COD = 1,5-cyclooctadiene; p-psb = 1,4-bis(dimethyl-4-pyridylsilyl)benzene; m-psb = 1,4-bis(dimethyl-3-pyridylsilyl)benzene] in a mixture of acetone and ethanol at room temperature produce the metallacyclodimers [PdCl 2( p- or m-psb)] 2. The cyclodimeric species of [PdCl 2( p-psb)] 2 at the boiling temperature or via the sonication of the chloroform solution is completely converted to the cyclotrimer [PdCl 2( p-psb)] 3. Direct reaction of (COD)PdCl 2 with p-psb in a mixture of acetone and ethanol at reflux temperature yields the same trimer, [PdCl 2( p-psb)] 3. Furthermore, equilibria between the kinetic product, [PdCl 2( p-psb)] 2, and the thermodynamic product, [PdCl 2( p-psb)] 3, have been observed in N, N-dimethylformamide as well as in dimethyl sulfoxide. In contrast, the cyclodimeric structure of [PdCl 2( m-psb)] 2 is retained under the same treatment conditions for 40 h; that is, the trimeric species, [PdCl 2( m-psb)] 3, is not formed. Such a notable difference between [PdCl 2( p-psb)] 2 and [PdCl 2( m-psb)] 2 might be explained by their different angle constraints.
Na
Young Mee
YM
Department of Chemistry and Center for Plastic Information Systems, Pusan National University, Pusan, Korea.
Noh
Tae Hwan
TH
Chun
In Sung
IS
Lee
Young-A
YA
Hong
Jongki
J
Jung
Ok-Sang
OS
D034242:Cyclooctanes / Q000737:chemistry*; D019281:Dimerization; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004126:Dimethylformamide / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D010165:Palladium / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D013997:Time Factors
D034242:Cyclooctanes; D008024:Ligands; D009942:Organometallic Compounds; D012996:Solutions; D012997:Solvents; C528600:bis(chloro)-1,4-bis(dimethyl-3 or 4-pyridylsilyl)benzenepalladium(II); D010165:Palladium; D004126:Dimethylformamide; C008756:palladium chloride; D004121:Dimethyl Sulfoxide