Versatile Coordination Modes and Transformations of the Cyclooctatriene Ligand in Ru(C₈H₁₀)L₃ (L = Tertiary Phosphine)

Reaction of Ru( η 4 -C 8 H 12 )( η 6 -C 8 H 10 ) ( 1 ) or Ru( η 4 -C 8 H 11 ) 2 ( 2 ) with tertiary phosphines gives Ru( η 4 -C 8 H 10 )L 3 [L = PMe 3 ( 4a ), PMe 2 Ph ( 4b ), PEt 3 ( 4c ), PEt 2 Ph ( 4d ), P(n-Bu) 3 ( 4e )]. The cyclooctatriene moiety in 4a oxidatively adds to the ruthenium, giving Ru(6- η 1:1−3- η 3 -C 8 H 10 )L 3 [L = PMe 3 ( 3a ), PMe 2 Ph ( 3b )]. Complexes 4c − e dissociate one phosphine ligand in solution, affording the (hydrido)ruthenium complexes RuH( η 5 -C 8 H 9 )L 2 [L = PEt 3 ( 5c ), PEt 2 Ph ( 5d ), P(n-Bu) 3 ( 5e )]. Whereas prolonged heating of 4c at 70 °C caused disproportionation of the η 4 -C 8 H 10 moiety giving a mixture of the cyclooctatetraene complex Ru( η 4 -C 8 H 8 )(PEt 3 ) 3 ( 6 ) and RuH( η 5 -C 8 H 11 )(PEt 3 ) 2 ( 7 ), heating of 1 with PEt 3, 4c, or 4d in the presence of 1,5-C 8 H 12 at 70 °C gave Ru( η 4 -bicyclo[4.2.0]octa-2,4-diene)L 3 [L = PEt 3 ( 8a ), L = PEt 2 Ph ( 8b )]. The molecular structures of 3b, 4c, 6, and 8b have been established by X-ray structure analysis.