Synthesis, structures, characterization, dynamic behavior, and reactions of novel late transition metal(H) 1-azaallyls

A series of homoleptic late transition metal(II) 1-azaallyl compounds ([M(L)(2)] {L = eta(3)N(SiMe3)C(Bu-t)CH(C6H4Me-4), M = Fe (5), Co (6), or Ni (7)}, [M(L-1)(2)] {L-1 = eta(3)-N(SiMe3)C(Ph)CH(SiMe3), M = Ni (8) or Pd (9)}, [M(L-2)(2)] {L-2 = eta(3)-N(SiMe3)C(Bu-t)CH(SiMe3), M = Fe (10) or Co (11)}, or [M(L-3)(2)] {L-3 = eta(1)-N(SiMe3)C(Bu-t)CH(C10H7-1), M = Fe (12)} have been prepared by reactions of anhydrous late transition metal halides {MX2 = FeBr2, CoCl2, [NiBr2(dme)], or [PdCl2(cod)]} with the appropriate lithium or potassium 1-azallyl KL (1), [LiL1(thf)](2) (2), [LiL2](2) (3), or KL3 (4) in a 1:2 molar ratio. The heteroleptic 1-azallylnickel(II) complex Ni(eta(3)-C3H5)(L-3) (13) was prepared from [{Ni(eta(3)-C3H5)(mu-Br)}(2)] with a stoichiometric amount of the 1-azaallylpotassium reagent KL3 (4). Single-crystal X-ray analysis revealed the 1-azaallyl to be bonded to the metal center in an eta(3)-NCC mode in the mononuclear compounds 5-8 and 10, whereas in 12 the 1-azallyl is N-bound in the kappa(1)-enamido fashion. The iron(II) (5, 10, and 12) and cobalt(II) (6 and 11) compounds are paramagnetic and have magnetic moments in the range 5.01-5.61 mu(B) and 2.73-3.01 mu(B), respectively, characteristic of a high-spin d(6) and low-spin d(7) electronic configuration, respectively. The diamagnetic group 10 metal 1-azaallyl compounds (7-9 and 13) were fully characterized by multinuclear NMR spectroscopy and were found to be a mixture of isomers. Several NOE, two-dimensional, and saturation transfer NMR spectroscopic experiments were used to elucidate the nature of the three isomers. Variable-temperature and variable-temperature saturation transfer NMR spectroscopic experiments showed the isomers of each of compounds 7-9 to be involved in a dynamic process. Electrochemical and oxidation studies on compounds 5 and 6 are reported, as are alpha-olefin oligomerization reactions catalyzed by 13 with MAO or B(C6F5)(3).