Verschiedenartige Koordinationen bei η 2 ‐Alken)‐(η 5 ‐cyclopentadienyl)organylnickel(II)‐Komplexen

Various Coordinations in (η 2 ‐Alkene)(η 5 ‐cyclopentadienyl)organylnickel(II) Complexes A series of (η 2 ‐alkene)(η 5 ‐cyclopentadienyl)organylnickel(II) complexes with substituted cyclopentadienyl ligands is synthesized in order to compare the structures, the thermal stabilities, and chemical reactivities. In (allyl)(η 5 ‐Cp')Ni compounds the allyl moiety is η 3 ‐coordinated when Cp'=C 5 H 5 , C 5 Me 5 ( 1 ), C 5 Ph 5 ( 2 ), indenyl ( 3 ), [Hydridotri(pyrazolyl)borato] ( 4 ) (as an equivalent of the cyclopentadienyl ligand), and [C 5 H 4 ((CH 2 ) 3 CHCH 2 )] ( 22 ). It is found that the [(η 2 ‐alkene)alkyl(η 5 ‐Cp')nickel] compounds [Cp'=C 5 Me 5 ; alkeneC 2 H 4 , alkyl=Me ( 10 ), Et ( 9 ) or alkene=(1 – 2‐η 2 )‐1,3‐butadiene, alkyl=Me ( 11 ); Cp'=C 5 Ph 5 ; alkene=C 2 H 4 , alkyl=Me ( 12 )] are thermally more stable and less reactive than their η 5 ;‐ C 5 H 5 analogues; the largest increase in thermal stability is observed when the η 5 ‐Cp' and the η 2 ‐alkene functions are connected by substitution of the cyclopentadienyl ligand with an alkenyl group of suitable chain length. In the case of compounds of the general type [(η 5 ‐C 5 R 4 ((CH 2 ) n CHCH 2 ))‐(ligand)Ni(II)] with Ph 3 P as the ligand these complexes are cationic [RH, n =3 ( 14 + ) or RMe, n =2 ( 17 + )]. On the other hand, the compounds with anionic ligands are neutral complexes (RH, n =3, ligand=methyl ( 19 ), ethyl ( 20 ), isopropyl ( 21 ) or RMe, n =3 and ligand=iodide ( 24 ), bromide ( 25 ), methyl ( 26 ), ethyl ( 27 )]. In 14 + , 17 + , 19 – 21 and 24 – 27 the CC bond of the alkenyl group is η 2 ‐coordinated to the nickel atom. X‐ray structures have been determined for 4 and 25 .