Hydrolysis of ester phosphates mediated by a copper complex.

Phosphate ester hydrolysis is an important reaction that plays a major role in both enzymatic and non-enzymatic processes, including DNA and pesticide breaking. Although it is a widely studied reaction, the precise mechanistic details, especially for copper complexes, remain under discussion. To contribute to the debate, we present the catalyzed hydrolysis of phosphomono-, di- and tri-esters mediated by the [Cu(II)(1,10-phenanthroline)] complex. The reaction coordinates for several substrates were explored through the metadynamics formalism. Thus, we found that for mono- and di-substituted ester phosphates a concerted mechanism is observed, where a coordinated hydroxyl group attacks the phosphorus atom at the same side as the leaving group, along with a proton transfer. In contrast, tri-substituted phosphate remains coordinated with the metal, and the nucleophile acts independently following an addition-elimination process. That is, the metallic complex achieves a specific nucleophile-phosphate interaction that produces a concerted transition state in the phosphoester hydrolysis process.

Aluminum-Triggered Condensation of Vicinal Silicate Groups into a Bicyclic Alumosilicate.

The molecular alumosilicates AlL{OSi(OtBu)2O}[OSi{(µ3-O)(MR2)2(µ-OtBu)}(OtBu)] (L = HC[CMeNAr]2-, where M = Al, R = Me (2), Et (3), and iBu (4) and M = Ga, R = Me (5)) were obtained from the reaction of AlL{OSi(OtBu)2(OH)}2 (1) with 1 or 2 equiv of the respective organometallic precursor. These compounds have a central bicyclic inorganic core formed by a six-membered AlSi2O3 alumosilicate ring with a Si-O-Si unit connected via a Si-O bond to a four-membered Al2O2 alumoxane ring. These compounds are formed even though 1 is specifically designed to yield 4R alumosilicate rings that would obey the Löweinstein's and Dempsey's rules about concatenation between silicon and aluminum tetrahedra in alumosilicates. We propose a mechanism for this rearrangement, based on the experimental evidence and density functional theory calculations, that involves a κ3µ2 coordination of a silicate unit to two AlMe2 groups, which weakens one Si-O bond and explains how aluminum atoms can cleave Si-O bonds. Furthermore, formation of the products experimentally confirms the theory that Al-O-Al groups can exist in alumosilicates if the oxygen atom belongs to an OH moiety.