The organometallic chemistry of aqueous ruthenium(II) with functionalized olefins: complex formation, isomerization, and metathesis chain transfer

Citation

McGrath, Dominic V. (1992) The organometallic chemistry of aqueous ruthenium(II) with functionalized olefins: complex formation, isomerization, and metathesis chain transfer. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/cdnv-xe78. https://resolver.caltech.edu/CaltechTHESIS:08312011-153706837

Abstract

The chemistry of aqueous Ru^(II)(H_2O)_6(tos)_2(tos = p-toluene sulfonate)(1) with functionalized olefins has been investigated. Complexes of the type (H_2O)_5Ru^(II)(olefin)(tos)_2 are formed from 1 and monoolefins. Dienes such as diallyl ether and 1,5-hexadiene displace two aquo ligands from 1 to form chelate complexes of the type (H_2O)_4Ru^(II)(olefin)_2(tos)_2. Chelation of oxygen containing functionalities such as alcohols, ethers, and sulfonates has also been observed when the functional group is a specified distance from the olefin. Thus, 3-buten- 1-o1, 3-butenyl methyl ether, and 2-propenesulfonate anion form chelate complexes Ru^(II)(H_2O)_4(η^1(O): η^2(C,C')-HOCH_2CH_2CH=CH_2)(tos)_2, Ru^(II)(H_2O)4-( η^1(O): η^2(C,C')-CH_3OCH_2CH_2CH=CH_2)(tos)_2, and Ru^(II)(H_2O)_4(η^1(O): η^2(C,C')OSO_2CH_2CH=CH_2)(tos), but allyl ethyl ether forms only the olefin complex Ru^(II)(H_2O)_5(η^2(C,C')-CH_2=CHCH_2OCH_2CH_3)(tos)_2. Carboxylic acid functionalities react irreversibly with 1 to form carboxylate complexes. 3-Pentenoic acid reacts with 1 yielding the bis(olefin)-bis(carboxylate) complex Ru(H_2O)_2(η^1(O), η^2-(C,C’)-OCOCH_2CH=CHCH_3)_2 which has been structurally characterized. Olefin isomerization of allylic ethers and alcohols is catalyzed by 1 under mild conditions in aqueous solution to yield the corresponding carbonyl compounds. Non-allylic olefins are also isomerized, although homoallylic alcohols exhibit stability towards isomerization. An exclusive 1,3-hydrogen shift is observed in the 1-catalyzed isomerization of allyl-1,1-d_2 alcohol to propionaldehyde-1,3-d_2 and allyl-1,1-d_2 methyl ether to 1-propenyl-1,3-d_2 methyl ether. The presence of crossover products from the isomerizations of mixtures of (a) allyl-3-^(13)C alcohol and allyl-1,1-d_2 alcohol and (b) allyl-1,1-d_2 methyl ether and allyl ethyl ether demonstrates that the isomerization of both ethers and alcohols occurs via intermolecular hydrogen shifts. A modified metal hydride addition-elimination mechanism involving exclusive Markovnikov addition to the double bond directed by the oxygen functionality of the substrate has been proposed. The acyclic terminal olefins 3-buten-1-ol and methyl acrylate are effective chain transfer agents in the ROMP the 7-oxanorbornene derivative 5,6-exobis(methoxymethyl)-7-oxabicyclo[2.2.1]hept-2-ene by 1, providing the first example of acyclic olefin metathesis in this system. Oligomer samples with M_n as low as 2K have been prepared. End groups corresponding to the alkylidene moieties of the chain transfer agents have been identified in the ^1H and ^(13)C NMR of the oligomer mixtures. Connectivity has been established between these end groups and the polymer chain through two-dimensional ^1H NMR. Ring-opened monomer units end capped by the chain transfer agent have been identified by mass spectrometry techniques.

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