Mechanistic Study on the Platinum-Catalyzed Reaction between Disilacyclobutene and Acetylene

Abstract

The mechanism and energetics of the Pt(PPh 3 ) 2 -catalyzed reaction between disilacyclobutene and acetylene are considered from density functional theory calculations at the B3LYP/6-31G**+LanL2DZ level using reasonable models. The catalytic cycle involves the following elementary processes: (1) oxidative addition of the Si-Si bond of disilacyclobutene to Pt, (2) release of one phosphine ligand, (3) coordination of acetylene to form a π-complex, (4) migratory insertion of acetylene into a Pt-Si bond leading to an Si-C bond, (5) coordination of acetylene, and (6) elimination of product disilacyclohexadiene. The ratedetermining step is the insertion of acetylene into a Pt-Si bond. Its activation energy of 23.0 kcal/mol is lower than that of the ring opening of disilacyclobutene, 41.5 kcal/mol, in the thermal reaction between disilacyclobutene and acetylene, which occurs at 250°C (Yoshizawa, K.; Kang, S.-Y.; Yamabe, T.; Naka, A.; Ishikawa, M. Organometallics 1999, 18, 4637). Therefore this Pt-catalyzed reaction should proceed under milder conditions. There are two possible reaction pathways in the initial stages of this catalytic cycle; one is the addition of disilacyclobutene, and the other is the addition of acetylene, the former being energetically more preferred than the latter in the initial stages of this reaction. Our calculations demonstrate that this Pt-catalyzed reaction should proceed stereospecifically.

Synthesis, characterization, reactivity and theoretical studies of ruthenium carbonyl complexes containing ortho-substituted triphenyl phosphanes

“…They can stabilize charge on a metal centre [1,2], generate vacancies for coordination [3,4], or favour a specific geometrical configuration in a metal complex providing high catalytic selectivity towards specific products [5]. They can also act as pro-chiral ligands helping in the obtaining of chiral products for pharmaceutical applications [6].…”

Dinuclear Palladium and Platinum Complexes with Bridging Silylene Ligands. Preparation Using (Aminosilyl)boronic Ester as the Ligand Precursor and Their Reactions with Alkynes

“…The reaction pathway is similar to those proposed for the reaction of alkynes with dinuclear Fe and Ru complexes . Disilametallacycles containing group 10 metal complexes have been investigated as possible intermediates in the bissilylation of unsaturated compounds catalyzed by these metal complexes , and have been prepared via Si–H or Si–Si bond activation of o -disilylbenzenes, o -disilylcarboranes, and disilacyclobutenes, and bis(disilane)s promoted by low-valent transition metals.…”

Stereochemistry of Disilanylene-Containing Cyclic Compounds. Palladium-Catalyzed Reactions of cis- and trans-3,4-Benzo-1,2-diisopropyl-1,2-dimethyl-1,2-disilacyclobut-3-ene with Ethylene

“…On the basis of the results obtained from the transition-metal-catalyzed double silylation of disilanes to alkynes, the formation of the adduct 2a in the palladium-catalyzed reaction of 1a with ethylene may be explained as follows: (1) insertion of the palladium species into a silicon–silicon bond in 1a , giving cis -3,4-benzo-2,5-diisopropyl-2,5-dimethyl-1-pallada-2,5-disilacyclopent-2-ene ( 4a ), (2) coordination of ethylene at the palladium atom in 4a , followed by insertion of a double bond of ethylene into a palladium–silicon bond to produce a palladium complex ( 5a ), and (3) reductive elimination of the palladium species from 5a to yield the adduct 2a . All reactions proceed with high stereospecificity, as shown in Scheme .…”

“…It is well-known that the benzodisilacyclobutenes bearing various substituents at the silicon atoms can readily be prepared by the sodium condensation reaction of 1,2-bis(dialkylchlorosilyl)benzenes in high yields. Many types of benzodisilacyclobutenes and benzobis(disilacyclobutenes) have been synthesized, and their thermal, photochemical, and transition-metal-catalyzed reactions have been studied. − The various types of the benzobis(silyl)metal complexes have also been synthesized by the reactions of 1,2-bis(hydrosilyl)benzenes with the transition-metal complexes, and their chemical properties have been investigated in detail. , In addition, theoretical investigations concerning thermal ring-opening reactions and transition-metal-catalyzed reactions of the disilacyclobutene derivatives have been reported . However, much less interest has been shown in the stereochemistry of the reactions of the benzodisilacyclobutenes with organic substrates.…”