作者:Sorin-Claudiu Roşca、Elsa Caytan、Vincent Dorcet、Thierry Roisnel、Jean-François Carpentier、Yann Sarazin
DOI:10.1021/acs.organomet.7b00006
日期:2017.4.10
pi ligands such as olefins and alkynes bind intramolecularly to the metal atom in d(0) complexes of the large alkaline earths (Ae) calcium and strontium supported by fluoroalkoxo ligands with dangling unsaturated C=C or C C bonds, and having the amide N(SiMe2H)(2)(-) as the coligand. These O-bridged dinuclear complexes are further stabilized by secondary C-F-->Ae and beta-Si-H center dot center dot center dot Ae interactions. In a set of structurally related Ca-olefin complexes, the strength of these interactions gradually increases as the coordination of the olefin onto Ca2+ becomes weaker (from eta(2)-coordinated to eta(1) to fully dissociated) upon increasing steric congestion, thus ensuring that over-whelming electronic depletion does not occur at calcium. NMR data imply that the olefins are metal-bound in [D-8]toluene solutions. The Ae center dot center dot center dot C-pi, C-F-->Ae, and beta-Si-H center dot center dot center dot Ae noncovalent interactions are also strong in the parent Ae-alkyne complexes, the first examples of non-acetylide Ae-alkynes compounds. Calcium-arene complexes could not be made, as the aromatic tether did not bind to the metal atom. Instead, a trinuclear complex with noninteracting C6H5 groups was obtained. It exhibits exceptionally strong C-F-->Ca and beta-Si-H center dot center dot center dot Ca interactions. NMR data indicate that the congeneric calcium-allene complex can be made, but it spontaneously isomerizes toward the more stable Ca-alkyne via an unusual 1,3-hydride shift intramolecular process.