摘要:
Reaction of HC(Me(2)pz)(3) with Mg{N(SiMe3)(2)}(2) gave the zwitterionic amide complex Mg{C(Me(2)pz)(3)}{N(SiMe3)(2)} (13), containing a free pyramidal carbanion and a cationic {Mg-N(SiMe3)(2)}(+) moiety. Reaction of the less bulky amide Mg{N(SiHMe2)(2)}(2) with RC(Me(2)pz)(3) (R = H or D) gave the four-coordinate adducts Mg{kappa N-2-RC(Me(2)pz)(3)}{N(SiHMe2)(2)}(2) (R = H (15) or D (15-d)). A similar complex, Mg{kappa N-2-HC(Me(2)pz)(3)}{N(SiMe3)(2)}(2) (14), was observed by NMR spectroscopy at low temperatures. On warming, 15, 15-d, and 14 eliminated RN(SiR'Me-2)(2) (R' = H or Me) to form Mg{C(Me(2)pz)(3)}{N(SiR'Me-2)(2)} (13 or 17). The reactions of 15 and 15-d followed first-order kinetics with a primary kinetic isotope effect (k(H)/k(D)) of 1.91(2). Reaction of 13 or 17 with a further equivalent of HC(Me(2)pz)(3) gave the homoleptic sandwich complex Mg{C(Me(2)pz)(3)}(2) (previously reported), containing two free carbanions and a dicationic metal center. The reaction of 17 with an excess of RC(Me(2)pz)(3) (R = H or D) followed pseudo-first-order kinetics with a primary kinetic isotope effect of 1.51(4). The corresponding reactions of Ca{N(SiMe3)(2)}(2)(THF)(2) with 1 or 2 equiv of HC(Me(2)pz)(3) gave Ca{C(Me(2)pz)(3)}{N(SiMe3)(2)}(THF) (18) or Ca{C(Me(2)pz)(3)}(2) (19). In contrast, Zn{N(SiMe3)(2)}(2) was effectively unreactive toward HC(Me(2)pz)(3). However, reaction of ZnCl2 with 1 or 2 equiv of Li{C(Me(2)pz)(3)}(THF) afforded Zn{C(Me(2)pz)(3)}Cl (20) or Zn{C(Me(2)pz)(3)}(2) (23), respectively. Subsequent reaction of 20 with NaN(SiMe3)(2) or LiN(SiHMe2)(2) formed Zn{C(Me(2)pz)(3)}{N(SiRMe2)(2)} (R = Me (21) or H). Cd{N(SiMe3)(2)}(2) reacted with 1 or 2 equiv of HC(Me(2)pz)(3) to form Cd{C(Me(2)pz)(3)}{N(SiMe3)(2)} (24) or Cd{C(Me(2)pz)(3)}(2) (25). Reaction of 13 or 18 with HC(pz)(3) gave the heteroleptic zwitterions M{C(Me(2)pz)(3)}{C(pz)(3)} (M = Mg (26) or Ca (27)), containing kappa N-3-coordinated C(Me(2)pz)(3) and C(pz)(3) ligands. In contrast, reaction of 24 with HC(pz)(3) formed Cd{C(Me(2)pz)(3)}{kappa C-1, kappa N-2-C(pz)(3)} (28), containing two different coordination modes for the tris(pyrazolyl)methanide ligands and a Cd-C(pz)(3) bond. The solid-state structures of 13, 15, 18, 19, 20, 21, 23, 24, 26, and 28 have been determined.