Phosphinimines as potential technetium environmental sensors

Phosphinimines, R3P=NSiMe3, undergo hydrolysis to form the phosphiniminium cation, R3P=NH2, which forms the ion pair [R3P=NH2][X] in the presence of an anion. Preliminary studies show that in the presence of TcO4, Ph3P=NSiMe3 forms [Ph3P=NH2][TcO4] and [Ph3P=NH2] is selective for TcO4 over other anions. Technetium-99 is present as environmental contamination in the form of TcO4, which is extremely mobile. Currently available methods to measure this contamination are time consuming and tedious. A method to preconcentrate and measure Tc environmental contamination in a quick and efficient manner is needed. The selectivity of the phosphiniminium cation for TcO4 may make phosphinimines suitable for such preconcentration and possibly for measurement. Several phosphinimines were synthesized and characterized for their stability and selectivity with TcO4, including Ph3P=NSiMe3, (9-anthracenyl)Ph2P=NSiMe3, (1-napthyl)Ph2P=NSiMe3, and (p-COOMe)C6H4Ph2P=NSiMe3. (9-anthracenyl)Ph2P=NSiMe3 and (1-napthyl)Ph2P=NSiMe3 include possible reporter groups and (p-COOMe)C6H4Ph2P=NSiMe3 contains a linking moiety for incorporating reporter groups or attaching the phosphinimine to a polymer support. The use of internal and external reporter groups to generate a signal in the presence of TcO4 is also investigated.