deprotonation of 
 [ u(trentips)(nh2 ) ] ( 1 ) [ trentips = n(ch2ch2nsipri3)3 ] with organoalkali metal reagents 
 mr ( m = li , r = but ; m = na  cs , r = ch2c6h5 ) afforded the imido - bridged dimers [ { u(trentips)(-n[h]m)}2 ] [ m = li  cs ( 2a  e ) ] . 
 treatment of 2c ( m 
 = k ) with 2 equiv of 15-crown-5 ether ( 15c5 ) afforded the uranium 
 terminal parent imido complex [ u(trentips)(nh)][k(15c5)2 ] ( 3c ) , which can also be viewed as a masked 
 uranium(iv ) nitride . 
 the uranium 
 imido linkage was found to 
 be essentially linear , and theoretical calculations suggested 24 polarized u 
 n multiple bonding . 
 attempts to oxidize 3c to afford the neutral uranium 
 terminal parent imido complex [ u(trentips)(nh ) ] ( 4 ) resulted in spontaneous disproportionation to give 1 and the uranium  nitride complex [ u(trentips)(n ) ] ( 5 ) ; this reaction is a new way to prepare the 
 terminal uranium  nitride linkage and 
 was calculated to be exothermic 
 by 3.25 kcal mol1 .