Pyridyl-Substituted Indenyl Ruthenium Complexes: Synthesis, Structures, and Reactivities

We have investigated the synthesis of a novel pyridyl-substituted indenyl trinuclear ruthenium complex, {mu(2),-eta(5) eta(1)-(C5H4N)(C9H5)}Ru-3(CO)(9) (1), and its reactivities with pyridine derivatives, PPh3, and different types of alkenes. Complex 1 was synthesized in 89% yield from Ru-3(CO)(12) and 3-(2-pyridypindene (1.1 mol ratio) in refluxing heptane. The reaction of 1 with a 5-fold excess of 3-(2-pyridyl)indene gave two complexes, {eta(1)-(C5H4N)(C9H6)}(2)Ru(CO)(2) (2) and {eta(5)-C5H4N)-(C9H6)}{eta(1)-(C5H4N)(C9H6)}Ru-2(CO)(4) (3). Both were also converted back to 1 in the presence of an equimolar amount of Ru-3(CO)(12), although the yields were low Reaction of 1 in refluxing toluene afforded an unexpected complex, (mu(3)-eta(6)center dot eta(3)center dot eta(1)-(C5H4N)(C9H5)}Ru-3(CO)(7) (4), via the loss of two CO groups Complex 4 represents a completely new type of coordination mode (mu(3)-eta(6)center dot eta(3) eta(1)) of indenyl ligands in transition metal complexes. The reactions of 1 with 2-(2-pyridyl)indene, 1,2,3,5-tetramethyl-4-(2-pyridyl)cyclopentadiene, 1,2-diphenyl-4-(2-pyridyl)cyclopentadiene, and 2-phenylpyridine in refluximg heptane afforded the mono- and/or dinuclear complexes 5-9 via the cleavage of either a Ru-C(eta(1)) or Ru-C(eta(5)) bond or both In the case of PPh3, only one of three carbonyls at the pyridyl-coordinated ruthenium center of 1 was replaced by PPh3 to produce {mu(2)-eta(5)center dot eta(1)-(C5H4N)-(C9H5)}Ru-3(CO)(8)(PPh3) (10). The reactions of 1 with various terminal alkenes (CH2=CHR) gave only the dinuclear ruthenium complexes {eta(5)-(C5H4N)(C9H5CHCH2R)}Ru-2(CO)(5) (11-13, 15, and 17) via the insertion of alkenes into the Ru-C(eta(1)) bond of 1 with the exception of 2-vinylpyridine and CH2=CHOCH2CH3, which reacted with 1 to yield the pyridyl-substituted complex {eta(5)-(C5H4N)-(C9H5CHCH2(C5H4N))}Ru-2(CO)(4) (14) and two unexpected complexes, 13 and {eta(5)-(C5H4N)-(C9H4CHCH2CH(OCH2CH3))}Ru-2(CO)(5) (18a and 18b), respectively. Complex 15 was also transformed to {eta(5)-(C5H4N)(C9H5CHCH2CO2CH3)}Ru-2(CO)(3)(eta(5)-CH2=CHCO2CH3) (16) in the presence of methyl acrylate The reactions of 1 with internal alkenes such as norbornene and cyclohexene gave complexes 19-22 in very low yields also via the insertion of alkenes into the Ru-C(eta(1)) bond of 1, with the concomitant formation of a small amount of 4. The molecular structures of 1-5, 8-11, 13-16, 18a, 186, and 21 weredetermined by X-ray diffraction analysis An alternative mechanism for the formation of dinuclear ruthenium complexes via the insertion of alkenes into the Ru-C( 71) bond is proposed.