Platinum silyl complexes structures

Metal chemical shifts have not found extensive use in relation to structural problems in catalysis. This is partially due to the relatively poor sensitivity of many (but not all) spin 1=1/2 metals. The most interesting exception concerns Pt, which is 33.7% abundant and possesses a relatively large magnetic moment. Platinum chemistry often serves as a model for the catalytically more useful palladium. Additionally, Pt NMR, has been used in connection with the hydrosilyla-tion and hydroformylation reactions. In the former area, Roy and Taylor [82] have prepared the catalysts Pt(SiCl2Me)2(l,5-COD) and [Pt()i-Cl)(SiCl2Me)(q -l,5-COD)]2 and used Pt methods (plus Si and NMR) to characterize these and related compounds. These represent the first stable alkene platinum silyl complexes and their reactions are thought to support the often-cited Chalk-Harrod hydrosilylation mechanism. 

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>. 

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. 

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