Crystal structure of the dimeric 1:2 addition complex of tricarbonylmesitylenemolybdenum with mercury(II) chloride
Abstract
Crystals of the title compound [{(C6H3Me3)(CO)3Mo(HgCl2)2}2] are monoclinic, space group C2/c, a= 17.049(4), b= 13.599(3), c= 17.249(7)Å, β= 102.54°, Z= 8. The structure was determined from diffractometer data by the heavy-atom method and refined by full-matrix least-squares to R 0.035 (on F) for 1 598 reflections. The structure consists of centrosymmetric dimers in which the tricarbonylmesitylenemolybdenum groups are bonded to mercury [Mo–Hg 2.745(1)Å]; the central Hg2Cl2 four-membered ring has one molybdenumu bonded to each mercury. All the mercury atoms are four-co-ordinate; the mercury atoms not bonded to molybdenum are halogenbridged to the four-membered ring, extending the mercury–halogen network. The mercury–chloride distances range widely from 2.317(5) to 3.038(5)Å.
The upwards shift of 58 cm–1 of the averaged i.r. CO stretching frequencies on complex formation is due to this Lewis acid–base bonding.