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Reaction of HC(Me2pz)3 with Mg(N(SiMe 3)2}2 gave the zwitterionic amide complex Mg{C(Me2pz)3}{N(SiMe3)2} (13), containing a "free" pyramidal carbanion and a cationic {Mg-N(SiMe 3)2}+ moiety. Reaction of the less bulky amide Mg{N(SiHMe2)2}2 with RC(Me2pz) 3 (R = H or D) gave the four-coordinate adducts Mg{k 2N-RC(Me2pz)3}(N(SiHMe2) 2}2 (R = H (15) or D (15-d)). A similar complex, Mg{k 2N-HC(Me2pz)3}{N(SiMe3)2}2 (14), was observed by NMR spectroscopy at low temperatures. On warming, 15, 15-d, and 14 eliminated RN(SiR'Me2)2 (R' = H or Me) to form Mg{C(Me 2pz)3}{N(SiR'Me2)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(Me2pz)3 gave the homoleptic sandwich complex Mg{C(Me2pz)3}2 (previously reported), containing two free carbanions and a dicationic metal center. The reaction of 17 with an excess of RC(Me2Pz)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(Me2pz) 3 gave Ca{C(Me2pz)3}{N(SiMe3) 2}(THF) (18) or Ca{C(Me2pz)3}2 (19). In contrast, Zn{N(SiMe3)2}2 was effectively unreactive toward HC(Me2pz)3. However, reaction of ZnCl2 with 1 or 2 equiv of Li{C(Me2pz)3}(THF) afforded Zn{C(Me2pz)3}Cl (20) or Zn{C(Me 2pz)3}2 (23), respectively. Subsequent reaction of 20 with NaN(SiMe3)2 or LiN(SiHMe2) 2 formed Zn{C(Me2Pz)3}{N(SiRMe 2)2) (R = Me (21) or H). Cd{N(SiMe3) 2)2 reacted with 1 or 2 equiv of HC(Me2PZ) 3 to form Cd{C(Me2pz)3}{N(SiMe 3)2} (24) or Cd{C(Me2pz)3} 2 (25). Reaction of 13 or 18 with HC(pz)3 gave the heteroleptic zwitterions M{C(Me2pz)3}{C(pz)3} (M = Mg (26) or Ca (27)), containing k3AT-coordinated C(Me 2pz)3 and C(pz)3 ligands. In contrast, reaction of 24 with HC(pz)3 formed Cd{C(Me2Pz)3}{k 1C, K2N-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. © 2010 American Chemical Society. |
