“…A ligand that contains the additional donor atom (X) directly bound to nitrogen could be considered as the shortest case of a chelating amide; the proximity to the metal favors the η 2 binding mode (Chart , I ) over the η 1 mode (Chart , II ). Such coordination has been observed in [Li 2 ((CH 3 ) 3 Si−N−N(Si(CH 3 ) 3 )) 2 ] ( 7 ), [Li 2 ((CH 3 ) 2 ((CH 3 ) 3 C)Si−N−N(H)Si(C(CH 3 ) 3 )(CH 3 ) 2 ) 2 (THF) 2 ] ( 8 ), [Li 2 ((CH 3 ) 3 Si−N−N(H)C(CH 3 ) 3 ) 2 (THF) 2 ] ( 9 ), [Li 2 ((CH 3 ) 3 Si−N−N(CH 2 C 6 H 5 )Si(CH 3 ) 3 ) 2 ] ( 10 ), [Li 2 (C 6 H 5 −N−N(H)Si(CH 3 ) 3 ) 2 (Et 2 O) 2 )] ( 11 ), and [Li 2 (F((CH 3 ) 3 C) 2 Si−N−N(CH 3 ) 2 ) 2 (THF) 2 ] ( 12 ) . Softer X atoms are less effective in coordinating a hard cation; the only other structure of an amide featuring a third-period donor and η 2 coordination is that of [Li 2 (PhN−PPh 2 ) 2 (OEt 2 ) 2 ] ( 13 ) with a Li−P distance of 2.684(3) Å.…”