ETA-1-ALKANEIMIDOYL AND ETA-2-ALKANEIMIDOYL COMPLEXES OF NICKEL - SYNTHESIS AND PROPERTIES

The insertion of CNBut into the Ni-C bond of the alkyls trans-Ni(R)Cl(PMe3)2 gives the η1-alkaneimidoyls Ni[η1-C(NBut)R]Cl(PMe3)2 (R = CH3 (1), CH2CMe2Ph (2)), but for R = CH2SiMe3 and CH2CMe3, both η1 and η2 η3species can be isolated, Ni[η1-C(NBut)R]Cl(PMe3)2 (R = CH2SiMe3 (3), CH2CMe3 (4)), Ni[η2-C(NBut)R]Cl(PMe3) (R = CH2SiMe3 (5), CH2CMe3 (6)). Facile η1-η2 interconversions can be achieved; addition of PMe3 to solutions of 5 or 6 produces 3 or 4, respectively, while PMe3 removal from the η1 compounds affords the corresponding η2-alkaneimidoyls. The analogous insertion of CNBut into the Ni-C bond of the alkyl-pyrrolyls Ni(R)(NC4H2X2)(PMe3)2 affords only η2-alkaneimidoyl structures, Ni[η2-C-(NBut)R](NC4H2X2)(PMe3) (X = H, R = Me (7); X = Me, R = Me (8), CH2SiMe3 (9), CH2CMe3 (10)). On the other hand, the 18-electron η1-alkaneimidoyls CpNi[η1-C(NBut)R]PMe3 (R = Me (11), CH2CMe2Ph (12)) can be obtained by the reaction of NaCp with 1 and 2 respectively, while the interaction of 1 with NaS2CNMe2 yields Ni[η1-C(NBut)Me](S2CNMe2)PMe3 (13). The η1-alkaneimidoyls also undergo facile protonation to the corresponding cationic aminocarbene complexes, e.g., [Ni(C(NHBut)Me)Cl(PMe3)2]Cl (14a). All the η1-alkaneimidoyls display v(C=N) in the range 1630-1590 cm−1, while for the η2-alkaneimidoyls a shorter and higher frequency range is observed (1730-1710cm−1). In the η1-alkaneimidoyls, the nickel-bound carbon atom resonates at ca. 190-185 ppm (with the exception of the 18-electron complexes 11 and 12, for which δ(Ni-C) ≃ 177 ppm), while in the η2-alkaneimidoyls this resonance appears at ca. 170 ppm. © 1990, American Chemical Society. All rights reserved.