Formation of a Cyclobutylidene Ring:  Intramolecular [2 + 2] Cycloaddition of Allyl and Vinylidene CC Bonds under Mild Conditions

Abstract

Intramolecular [2 + 2] cycloaddition of two C=C bonds in vinylidene complexes [Ru(eta5-C9H7){=C=C(R)H}(PPh3){kappa1-(P)-PPh2(C3H5)][BF4] affords cyclobutylidene complexes [Ru(eta5-C9H7){kappa2-(P,C)-(=CC(R)HCH2CHCH2PPh2)}(PPh3)][BF4], which can be also obtained by reaction of terminal alkynes with [Ru(eta5-C9H7)(PPh3){kappa3-(P,C,C)-PPh2(C3H5)}][PF6]. The reaction proceeds under mild conditions via vinylidene complexes, and the activation parameters were determined by kinetic studies.

Mechanistic Investigations of the Iron(III)-Catalyzed Carbonyl-Olefin Metathesis Reaction

“…The Eyring data display high ΔH ‡ as well as negative ΔS ‡ values, consistent with ordered transition states relative to the resting state of the cycle. 25 Importantly, the transition states for oxetane formation and fragmentation will each be more ordered than the substrate-iron complex, requiring further analysis to determine the turnover-limiting step.…”

Synthesis of New Half‐Sandwich Ruthenium(II) Complexes Bearing Alkenyl‐ and Alkynylphosphane Ligands

“…The (R) enantiomer is shown in Figure 1. 6 ], [11][12][13] our interest focused on the synthesis of novel complexes with allyl-and homoallylphosphanes coordinated in a κ 3 P,C,C mode, which can be formed from complexes 1a,b and 2b by halide abstraction and subsequent olefin coordination to the metal. Thus, the treatment of complexes 1a,b with AgSbF 6 2 J P,P = 29.5 Hz) are found for complex 4b.…”

“…[10] We have previously reported the synthesis and characterization of the ruthenium() complexes [Ru(η 5 -C 9 H 7 )(PPh 3 )(Ph 2 PCH 2 C(R)=CH 2 -κ 3 6 ] (R = H, Me), which feature a κ 3 P,C,C coordination mode of the allyldiphenylphosphane as well as a diastereofacial coordination of the olefin at the ruthenium center. [11] Moreover, these complexes have been demonstrated to be useful for further transformations, particularly as substrates in stereoselective nucleophilic addition [11] and intramolecular cycloaddition reactions, [12,13] which lead to interesting ruthenaphosphacyclopentane and ruthenaphosphabicycloheptene complexes, respectively. The progress of the latter reaction confirms the hemilabile character of the allyldiphenylphosphane ligand, a fact that has been corroborated by kinetic studies.…”

Indenyl complexes of ruthenium containing thiolate ligands. Structure of IndRu(dppe)SPh

“…These complexes have been known as catalysts in many useful organic reactions [9][10][11][12][13][14][15][16][17][18]. The hydride complex, IndRu(dppm)H [Ind = g 5 -C 9 H 7 ; dppm = bis (diphenylphosphino)methane], is an active catalyst for the hydrogenation of nitriles to amides [9].…”

“…The acetylide complexes, IndRu(P) 2 (C " CR) (P = PPh 3 , 1/2dppm, 1/2dppe, 1/2dppp, R = alkyl, aryl) were reacted with NO in the presence of NaClO 4 to give the corresponding nitriles and the ruthenium salts [IndRu(P) 2 (CO)]ClO 4 [11]. The vinylidene complexes, [IndRu(PR 3 )(L)(=C=CR 2 )] + (L = PR 3 , CO), undergo [2 + 2] cycloaddition reactions with a variety of unsaturated species as alkynes, imines, azabutadienes and metal alkynes [12][13][14][15][16][17][18].…”