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

Abstract

We have investigated the synthesis of a novel pyridyl-substituted indenyl trinuclear ruthenium complex, {μ 2 -η 5 :η 1 -(C 5 H 4 N)(C 9 H 5 )}Ru 3 (CO) 9 (1), and its reactivities with pyridine derivatives, PPh 3 , and different types of alkenes. Complex 1 was synthesized in 89% yield from Ru 3 (CO) 12 and 3-(2-pyridyl)indene (1:1 mol ratio) in refluxing heptane. The reaction of 1 with a 5-fold excess of 3-(2-pyridyl)indene gave two complexes, {η 1 -(C 5 H 4 N)(C 9 H 6 )} 2 Ru(CO) 2 (2) and {η 5 -(C 5 H 4 N)-(C 9 H 6 )}{η 1 -(C 5 H 4 N)(C 9 H 6 )}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, {μ 3 -η 6 :η 3 :η 1 -(C 5 H 4 N)(C 9 H 5 )}Ru 3 (CO) 7 (4), via the loss of two CO groups. Complex 4 represents a completely new type of coordination mode (μ 3 -η 6 :η 3 :η 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 refluxing heptane afforded the mono-and/or dinuclear complexes 5-9 via the cleavage of either a Ru-C(η 1 ) or Ru-C(η 5 ) bond or both. In the case of PPh 3 , only one of three carbonyls at the pyridyl-coordinated ruthenium center of 1 was replaced by PPh 3 to produce {μ 2 -η 5 :η 1 -(C 5 H 4 N)-(C 9 H 5 )}Ru 3 (CO) 8 (PPh 3 ) (10). The reactions of 1 with various terminal alkenes (CH 2 dCHR) gave only the dinuclear ruthenium complexes {η 5 -(C 5 H 4 N)(C 9 H 5 CHCH 2 R)}Ru 2 (CO) 5 (11-13, 15, and 17) via the insertion of alkenes into the Ru-C(η 1 ) bond of 1 with the exception of 2-vinylpyridine and CH 2 dCHOCH 2 CH 3 , which reacted with 1 to yield the pyridyl-substituted complex {η 5 -(C 5 H 4 N)-(C 9 H 5 CHCH 2 (C 5 H 4 N))}Ru 2 (CO) 4 ( 14) and two unexpected complexes, 13 and {η 5 -(C 5 H 4 N)-(C 9 H 4 CHCH 2 CH 2 CH(OCH 2 CH 3 ))}Ru 2 (CO) 5 (18a and 18b), respectively. Complex 15 was also transformed to {η 5 -(C 5 H 4 N)(C 9 H 5 CHCH 2 CO 2 CH 3 )}Ru 2 (CO) 3 (η 5 -CH 2 dCHCO 2 CH 3 ) (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(η 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, 18b, and 21 were determined by X-ray diffraction analysis. An alternative mechanism for the formation of dinuclear ruthenium complexes via the insertion of alkenes into the Ru-C(η 1 ) bond is proposed.

Synthesis and Structures of Ruthenium Carbonyl Complexes Bearing Pyridine-Alkoxide Ligands and Their Catalytic Activity in Alcohol Oxidation

“…In complexes 1a - 1h , the distances between the two Ru atoms directly connected to the ligands are in the range of 3.0236(10)-3.0516(10) Å, which are comparable to the Ru–Ru bond distances in complexes (μ-OC 6 H 4 OMe-2) 2 Ru 3 (CO) 8 (3.012(1) Å) (Santini et al, 1987) and [PyCH = C(Ph)O] 2 Ru 3 (CO) 8 (3.0693(6) Å) (Ma et al, 2017). The bond lengths of Ru(1)–N(1) varying from 2.252(7) Å to 2.330(14) Å observed in all complexes are slightly longer than those Ru–N bond lengths found in complexes {μ 2 -μ 5 :η 1 -(C 5 H 4 N)(C 9 H 5 )}Ru 3 (CO) 9 [2.164(3) Å] (Chen et al, 2010) and (6-bromopyCMeC 6 H 5 O)Ru 3 (CO) 9 (2.229(4) Å) (Hao et al, 2018b). The Ru(1)–O(1) bond lengths for 1a - 1h are all similar and are in the range of 2.072(3)-2.093(5) Å, showing that the substitutions at 2- or 4- positions of benzene ring have no significant effect on bond lengths.…”

Reactions of a Trinuclear Ruthenium Complex Derived from 3-(2-Pyridyl)indene with Diphenylacetylene and Phenylacetylene: Insertion of Alkynes into the Ru−C bond

“…For example, functional group directed aromatic C−H/alkyne coupling is an effective method not only to introduce olefinic groups to the ortho position of an aromatic ring but also to synthesize various heterocycles. − ,− However, in some cases, terminal alkynes were not suitable, partly because of their oligomerization . We have recently reported the reactions of the trinuclear complex {μ 2 -η 5 :η 1 -(C 5 H 4 N)(C 9 H 5 )}Ru 3 (CO) 9 ( 1 ), derived from 3-(2-pyridyl)indene, with alkenes, giving a series of C−C coupling products via 1,1-insertion of alkenes into the Ru−C(η 1 ) bond . Here we further report its reactions with diphenylacetylene and phenylacetylene.…”

Reactivity of a trinuclear ruthenium complex involving C–H activation and insertion of alkene

“…[1][2][3][4][5][6][7][8][9] The indenyl metal complexes containing a donor-functionalized side chain have been receiving much attention. 10,11 For the pyridyl side-chain-functionalized indenyl ligands, the nitrogen atom can act as a good two-electron donor site and can coordinate to a variety of metals, and intramolecular coordination to a Lewis acidic metal center or construction of oligonuclear metal complexes usually shows different structures and reactivities. [12][13][14][15] In addition, some cyclopentadienyl metal complexes containing a substituted donor-functionalized side chain and a Cp*Ru cluster that C-H activates pyridine have been reported.…”