14-Electron Disilene Palladium Complex Having Strong π-Complex Character

The first 14-electron disilene palladium complex η2-[tetrakis(tert-butyldimethylsilyl)disilene](tricyclohexylphosphine)palladium (4) was synthesized. In the solid state, complex 4 has one tricyclohexylphosphine ligand bound unsymmetrically to the palladium center in regard to the η2-disilene moiety. The elongation of the Si−Si bond length from that of the corresponding free disilene (3.2%) and the bent back angles of the disilene moiety (4.41° and 9.65°) for 4 were much smaller than those for the corresponding 16-electron η2-disilene complex (Me3P)2Pd[tetrakis(tert-butyldimethylsilyl)disilene] (4.6% and 27.2°, respectively). Complex 4 is regarded as the complex having the strongest π-complex character among the known disilene complexes. Highly symmetric NMR spectra were observed for 4; central Si1 and Si2 nuclei were equivalent and appeared as a doublet with 2J(29Si−31P) of 19 Hz, indicating facile flipping of the phosphine ligand in the Pd−Si−Si plane.