title: 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.
abstract: 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.
authors.affiliation: Department of Chemistry and Center for Plastic Information Systems, Pusan National University, Pusan, Korea.
authors.forename: Young Mee
authors.initials: YM
authors.lastname: Na
authors.forename: Tae Hwan
authors.initials: TH
authors.lastname: Noh
authors.forename: In Sung
authors.initials: IS
authors.lastname: Chun
authors.forename: Young-A
authors.initials: YA
authors.lastname: Lee
authors.forename: Jongki
authors.initials: J
authors.lastname: Hong
authors.forename: Ok-Sang
authors.initials: OS
authors.lastname: Jung
mesh_terms: 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
chemical_list: 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