Less Is More: Three‐Coordinate C,N‐Chelated Distannynes and Digermynes

We report here the synthesis of new C,N‐chelated chlorostannylenes and germylenes L 3 MCl (M=Sn( 1 ), Ge ( 2 )) and L 4 MCl (M=Sn( 3 ), Ge ( 4 )) containing sterically demanding C,N‐chelating ligands L 3, 4 (L 3 =[2,4‐di‐ t Bu‐6‐(Et 2 NCH 2 )C 6 H 2 ] − ; L 4 =[2,4‐di‐ t Bu‐6‐{(C 6 H 3 ‐2′,6′‐ i Pr 2 )N=CH}C 6 H 2 ] − ). Reductions of 1 – 4 yielded three‐coordinate C,N‐chelated distannynes and digermynes [L 3, 4 M ] 2 for the first time ( 5 : L 3 , M=Sn, 6 : L 3 , M=Ge, 7 : L 4 , M=Sn, 8 : L 4 , M=Ge). For comparison, the four‐coordinate distannyne [L 5 Sn] 2 ( 10 ) stabilized by N,C,N‐chelate L 5 (L 5 =[2,6‐{(C 6 H 3 ‐2′,6′‐Me 2 )NCH} 2 C 6 H 3 ] − ) was prepared by the reduction of chlorostannylene L 5 SnCl ( 9 ). Hence, we highlight the role of donor‐driven stabilization of tetrynes. Compounds 1 – 10 were characterized by means of elemental analysis, NMR spectroscopy, and in the case of 1 , 2 , 5 – 7 , and 10 , also by single‐crystal X‐ray diffraction analysis. The bonding situation in either three‐ or four‐coordinate distannynes 5 , 7 , and 10 was evaluated by DFT calculations. DFT calculations were also used to compare the nature of the metal–metal bond in three‐coordinate C,N‐chelating distannyne [L 3 Sn] 2 ( 5 ) and related digermyme [L 3 Ge] 2 ( 6 ).