Intramolecular [2 + 2] Cycloaddition of Allyl CC and Allenylidene C_αC_βBonds:  Formation and Deprotonation of Cyclobutylidene Rings

Abstract

Ph (3b), H (3c), Me (3d)). The formation of complexes 3a-d and 4a-c proceeds through an intramolecular cycloaddition of the CdC allyl and C R dC β bonds in the intermediate allenylidene complexesThe allenylidene complex [Ru(η 5 -C 9 H 7 )(dCdCdCPh 2 ){κ 1 (P)-Ph 2 PCH 2 CHdCH 2 }(PPh 3 )][PF 6 ] (5) has been isolated from the reaction of 2a with 1,1diphenyl-2-propyn-1-ol in CH 2 Cl 2 . The deprotonation of complexes 3a-d and 4a with potassium tert-butoxide gives rise to the neutral complexes [Ru(η 5 -C n H m ){κ 2 (P,C)-{CdC-

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

“…Analytical and spectroscopic data (IR and 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectroscopy) support the proposed formulation (see Experimental Section for details). In particular, the IR spectra show the strong characteristic ν(CO) absorption at 1940 (1a and 1c) and 1930 cm -1 (1b) as well as the ν(CϵC) absorption at 2176 cm -1 (1c), a singlet resonance is observed at δ = 45.0 (1a), 44.0 (1b) and 22.5 ppm (1c) for the phosphanes in the 31 P{ 1 H} NMR spectra, and a low-field doublet signal is observed in the 13 C{ 1 H} NMR spectra due to the carbonyl group at δ = 203.0 (1a), 203.5 (1b) and 202.4 ppm (1c) [ 2 J C,P Ϸ 20.7-21.3 Hz]. The 13 C{ 1 H} NMR spectrum of 1c also shows two doublet signals for the alkynyl carbon nuclei at δ = 84.1 (J C,P = 93.6 Hz) and 108.9 ppm ( 2 J C,P = 14.4 Hz).…”

“…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.…”

“…[13] In addition, the 31 P{ 1 H} NMR spectra remain unchanged over a wide temperature range, thus ruling out a dynamic process between the two diastereoisomers on the NMR time scale. Contrary to these results, the analogous derivative 6 ] was found to be fluxional, giving rise to a rapid equilibrium between the two diastereomeric conformations present in solution.…”

“…[15] The Ru(1)-C (25) Their analytical and spectroscopic data support the proposed formulations (see Experimental Section for details). [21] The most significant spectroscopic features are (a) the IR spectrum of 5a shows the ν(CO) absorption at 1920 cm -1 , (b) the 31 P{ 1 H} spectra of 5a and 5b show the resonance of the chelate-ring phosphorus atom at δ = 101.3 (singlet) and 91.8 ppm (doublet, 2 J P,P = 33.7 Hz), respectively, and (c) the 13 C{ 1 H} NMR spectra show a high-field signal for the Ru-CH 2 carbon (δ = -4.1 ppm for 5a; δ = 82 -0.7 ppm for 5b) and two signals for the olefinic carbons of 5a (δ = 116. 4 Complex 6 was characterized analytically and spectroscopically (see Experimental Section for details).…”

“…[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.…”