Synthesis and structural characterization of new bis(alkynylamidinato)lanthanide(III)-amides

Abstract Four new unsolvated lanthanide bis(alkynylamidinato) amide complexes [ c -C 3 H 5 –C C–C(NR) 2 ] 2 LnN(SiMe 3 ) 2 ( 2 : Ln = Ce, R =  i Pr; 3 : Ln = Ce, R = Cy; 4 : Ln = Nd, R = Cy; 5 : Ln = Ho, R = Cy) have been prepared in moderate to good isolated yields (37–67%) via three-component reactions between anhydrous LnCl 3 (Ln = Ce, Nd, Ho), Li[ c -C 3 H 5 –C C–C(NR) 2 ] - ( 1a : R =  i Pr, 1b : R = Cy) and KN(SiMe 3 ) 2 in a 1:2:1 M ratio in THF. The same compounds were also accessible by amination of the previously reported lanthanide bis(amidinate) chloro precursors [ c -C 3 H 5 –C C–C(NR) 2 ] 2 Ln( μ -Cl) 2 ] and [ c -C 3 H 5 –C C–C(NR) 2 ] 2 Ho( μ -Cl) 2 Li(THF)(Et 2 O) with KN(SiMe 3 ) 2 . However, this synthetic protocol gave significantly lower yields of 2 – 5 (17–42%). The molecular structures of 4 and 5 have been authenticated through single-crystal X-ray diffraction. An initial catalytic study showed that the new complexes cannot be reliably employed as precatalysts for hydroamination/cyclization reactions.