Observation of carbonyl oxygen–π interaction in a metal complex

X-ray crystallography shows that [Ag2L2(H2O)2](BF4)2 where L is a 1:1 condensate of 1,2-diphenylethane-1,2-dione and 2-(2-aminoethyl pyridine), contains an Ag(I)–Ag(I) bond of length 2.979(2) Å and an angular, intraligand interaction of the keto O with the π cloud of the pyridine moiety (O-pyridine centroid = 3.12 Å). Model MP2/6-311++G(d,p) calculations indicate that the observed lone pair–π type interaction is stabilising and not merely a tolerated short contact.