The reactions of WClz(NPh)(PMePh2)3 with a number of triphenylphosphoranes weresurveyed, and alkylidene transfer to give W(=CHR)C12(NPh)(PMePh2)2 was observed for variously substituted aryl ylides Ph3P=CHAr', where Ar' = C&, C6H4-p-Me, CsHd-m-Me, C6H4-o-Me, C&-p-OEt, C6H4-o-OMe, CsH4-p-CF3, C~F S , o-Np, and m-Np, for the vinyl ylide Ph3P=CH-CH=CMe2, and also for the bis(y1ide) Ph3P=CH-C6H4-CsH4-CH=PPhs. A mechanism is proposed for the transfer reaction. A crystal structure of W(=CHC6H4-p-Me)C12(NPh)(PMePh& indicated an octahedral geometry in which the two mutually trans phosphines and the alkylidene are cis to the apical imido ligand and the alkylidene substituent lies syn to the imido ligand. Reduction of WC12(N-2,6-C6H3-Me2)-[OCMe(CF3)2]2(THF) in the presence of a number of aryl ylides yielded the corresponding benzylidene complexes W(=CHA~')(N-~,~-C~H~-M~Z) [OCMe(CF3)2] 2(PPh3), which were stable in solution but only isolable upon addition of a stronger donor ligand than PPh3 (e.g., PMe3). Transfer of o-methoxybenzylidene from phosphorus to reduced WC12(NAr) [OCMe(CF3)2]2(THF) complexes was especially favorable, as chelation by the o-methoxy group aided the transfer reaction, stabilized the resulting product, and, hence, enabled the synthesis of several arylimido derivatives W(=CHC6H4-o-OMe)(NAr) [OCMe(CF3)2]2(THF), where Ar = Ph, 2,6-C&--Mez, and 2,6-C&--(i-Pr)z. Crystal structures of the o-methoxybenzylidene complexes, with and without T H F coordinated to tungsten, were obtained and supported donation by the o-methoxy group to tungsten. The o-methoxybenzylidene complexes rapidly polymerized norbornene but only slowly metathesized acyclic olefins.

No abstract

No abstract

Simple organic molecules can have many functions. The active ingredient in the corrosion inhibitor 3-(4-methylbenzoyl)propionate works because it addresses the metal sites of a surface through carboxylate groups, forms hydrogen bonds with surface hydroxide groups (see picture), and provides excellent surface coverage through efficient packing of substituted aromatic groups.

Two polymetallic iron(III) complexes 1 and 2 have been synthesised from the known corrosion inhibitor 3-(4-methylbenzoyl)-propionic acid HL1 and their crystal structures determined. Coordination geometries extracted from these structures have been used as the basis for molecular modelling onto idealised iron(III) oxide surfaces as an aid to understanding the efficacy of inhibitors of the 4-keto acid type. The proposed mode of action involves 1,3-bridging didentate coordination of the carboxylate function of L1 to two FeIII ions, hydrogen-bond formation between the 4-keto group of L1 and a bridging surface hydroxy group, as well as close packing of the aromatic end groups, which should generate a hydrophobic barrier on the surface. Adsorption isotherm experiments have been used to compare the strengths of binding of related carboxylic acids onto iron(III) oxide surfaces and indicate that the presence of the 4-keto function leads to the formation of significantly more stable surface complexes.