THE GAS-PHASE CHEMISTRY OF SILAMIDE IONS

A series of silamide (silanamide) anions, SiH3NH- (1), C6H5SiH2NH- (2) , CH3OSiH2NH- (3), and CH3SiF2NH- (4), has been studied in detail in a tandem flowing afterglow selected-ion flow tube. Their reaction chemi stry has been probed with CO2, CS2, COS, SO2, and N2O as well as a num ber of alcohols and other reagents and shows not only features expecte d from amides but also ones that result from silyl substitution. Colli sion-induced dissociations (CID) were carried out to expand our knowle dge of the effect of silyl substitution on amide behavior. A prevalent pattern for the CID behavior of anions 1-4 reveals that a substituent borne by silicon cleaves as an anion. The resulting fragments either separate immediately or the anion abstracts a proton before separation . The gas-phase acidities of SiH3NH2, FSiH2-NH2, C6H5SiH2NH2, CH3OSiH2 NH2, and CH3SiF2NH2 have been measured using bracketing techniques. Th e acidity values fall in a small range, indicating that beta-substitut ion effects on silicon are small. G2 computational studies have been u sed to probe the Si-H and N-H acidity of SiH3NH2, showing that the N-H position is the more strongly acidic one.