Reaction of o-C6F4(HgCl)2 (1), m-C6F4(HgCl)2 (2), C6F5HgCl (3), and C6F4H(HgCl) (4) with TMSCN in MeCN affords the corresponding organomercury cyanide derivatives o-C6F4(HgCN)2 (5), m-C6F4(HgCN)2 (6), C6F5HgCN (7), and C6F4H(HgCN) (8), respectively. These compounds have been characterized by elemental analysis, 1H, 13C, 19F, and 199Hg NMR, and IR spectroscopy. The infrared spectra of 5−8 display a cyanide stretching band in the range 2170−2183 cm-1, while their 199Hg NMR chemical shifts are all within the range −1170 to −1250 ppm. The crystal structures of [2·DMF], [5·MeCOH], [5·PhCOH], and 8 have been determined. In [2·DMF], the DMF molecule acts as a terminal ligand and coordinates one of the mercury centers through the formation of a Hg−O bond of 2.746(14) Å. A similar situation is encountered in [5·MeCOH] and [5·PhCOH], wherein the aldehyde ligand is terminally ligated to one of the mercury centers through a Hg−O bond of 2.855(19) and 3.009(12) Å, respectively. In these compounds, the neighboring molecules engage in long intermolecular Hg···N contacts. In [5·MeCOH], these interactions lead to the formation of a hexameric aggregate whose shape is reminiscent of a capsule. The ability of 5−8 to catalyze the cyanosilylation of benzaldehyde has been studied. While little or no product formation is observed when the pure cyanide derivatives 5−8 are employed as catalysts, their combination with TMSCl leads to the formation of active catalytic species. The combination of bidentate 5 and TMSCl provides the most active system. The results are rationalized on the basis of a working model in which TMSCl is activated by the halophilic bidentate fluorinated mercury derivative 5, which produces a catalytically active Lewis acidic silicon species.