Synthesis of ruthenium vinylidene complexes with dppe ligand and their cyclopropenation reaction

Aqueous Coordination Chemistry of H2: Why is Coordinated H2Inert to Substitution by Water intrans-Ru(P2)2(H2)H+-type Complexes (P2= a Chelating Phosphine)?

“…Complexes Id, Ie, and If were previously synthesized by a slightly different route, and the molecules prepared by the route in eq 2 were spectroscopically identical to the previously reported spectra. [19][20][21] Solutions containing I exhibit a singlet in the 31 P{ 1 H} NMR spectrum, confirming a trans geometry (Table 1). Slow cooling of concentrated solutions of Ia and Ib resulted in the precipitation of yellow crystals suitable for X-ray crystallographic analysis (Table 2).…”

Cyclization Reactions of Ruthenium Vinylidene Complexes

“…Synthesis of Vinylidene Complexes. Treatment of [Ru]C⋮CPh ( 1 , [Ru] = (η 5 -C 5 H 5 )(dppe)Ru, dppe = Ph 2 PCH 2 CH 2 PPh 2 ) with PhNCS in CH 2 Cl 2 at room temperature for 3 days affords the yellow [2 + 2] cycloaddition product ( 2 ). − On the basis of the chemical reactivity of the bis(triphenylphosphine) analogue of 2 , we believe that 2 exists in two forms: a four-membered-ring structure and a zwitterionic structure formed by cleavage of the C α −S bond of the four-membered ring. In the zwitterionic form the negative charge could be localized either at the S atom or at the N atom, thus rendering these atoms nucleophilic.…”

“…We therefore reacted alkyl halides with the dppe analogue of the four-membered-ring complex. Herein we report that these alkylation reactions yield a number of vinylidene complexes. − Subsequent deprotonation-induced-cyclization reactions of these vinylidene complexes form neutral heterocyclopentenyl complexes. , …”

Reactions of Ruthenium Cyclopropenyl Complexes Containing Pentamethylcyclopentadienyl Ligands

“…Metal vinylidene complexes have attracted considerable attention since they offer the possibility of development of new types of organometallic intermediates that may have unusual reactivity. − Extensive reviews on this subject have appeared recently. − The best entry into the transition metal vinylidene complexes is the addition of electrophiles to the electron-rich carbon of metal alkynyl complexes. − A theoretical study of vinylidene complexes indicated localization of electron density on C β (HOMO) and the electron deficiency at C α . , A study of the reaction of alcohols with ruthenium vinylidene complexes indicated that electron-withdrawing groups on the acetylide unit or on the metal facilitate nucleophilic attack on C α …”

“…Recently we demonstrated that the presence of an electron-withdrawing group at C γ of the vinylidene ligand combined with the cationic character of the ruthenium complex enhances the acidity of the proton at C γ . Thus deprotonation of such complexes could be readily achieved, and subsequent intramolecular cycloaddition could lead to the formation of cyclopropenyl complexes. ,,, For example, [Cp(PPh 3 ) 2 RuCC(Ph)CH 2 CN] + was found to undergo deprotonation to afford the cyclopropenyl complex Unfortunately, without a methoxy substituent, the three-membered ring readily undergoes electrophilic addition to cause ring opening in the presence of acid or other electrophiles. The presence of a methoxy substituent in the cyclopropenyl ring enhances the stability of the three-membered ring, and protonation of such a ruthenium complex yields a cyclopropenylium complex by loss of methanol.…”