Silyl isocyanides, structure

In the crystal structure of the octahedral complex 19, two isocyanide ligands occupy the apical positions and the four silyl ligands lie at the vertices of a distorted square with a platinum atom at the center. The isocyanide ligands have a trans orientation <1996JOM(521)405>. 

The structure of silyl cyanides was a matter of dispute for many years. Emeleus, Maddock and Reid (1941) prepared silyl cyanide by the reaction of SiH3I with solid AgCN. The normal cyanide structure was written for this product without comment. However, on the basis of analogy with carbon chemistry, MacDiarmid (1956) suggested that the compound should be formulated as an isocyanide, H3SiNC. The problem Was finally resolved by careful infrared and microwave spectral studies which showed that the normal cyanide, H3SiCN, is correct (Linton and Nixon, 1958 a Mutter and Bracken, 1960 Sheridan and Turner, 1960). 

New silyl platinum isocyanides 109 have been reported (Equation (15)) with crystal structures of the Bu and Pr derivatives confirming the m-structure indicated by NMR spectroscopy. In solution, the NMR spectra of the complexes of the less bulky PMes ligand indicate isomerism between the as- and frans-isomcrs, with the more bulky PEt3 derivative showing no tendency to isomerize. 

---