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Treatment of IrCl(3)x H(2)O with one equivalent of 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy) in N,N-dimethylformamide (dmf) afforded [IrCl(3)(dmf)(dtbpy)] (1). Alkylation of 1 with Me(3)SiCH(2)MgCl resulted in C--Si cleavage of the Me(3)SiCH(2) group and formation of the Ir(III) silyl dialkyl compound [Ir(CH(2)SiMe(3))(dtbpy)(Me)(SiMe(3))] (2), which reacted with tBuNC to afford [Ir(tBuNC)(CH(2)SiMe(3))(dtbpy)(Me)(SiMe(3))] ([2(tBuNC)]). Reaction of 2 with phenylacetylene afforded dimeric [{Ir(C[triple chemical bond]CPh)(dtbpy)(SiMe(3))}(2)(mu-C[triple chemical bond]CPh)(2)] (3), in which the bridging PhC[triple chemical bond]C(-) ligands are bound to Ir in a mu-sigma:pi fashion. Alkylation of 1 with PhMe(2)CCH(2)MgCl afforded the cyclometalated compound [Ir(dtbpy)(CH(2)CMe(2)C(6)H(4))(2-C(6)H(4)CMe(3))] (4), which features an agostic interaction between the Ir center and the 2-tert-butylphenyl ligand. The cyclic voltammogram of 4 in CH(2)Cl(2) shows a reversible Ir(IV)-Ir(III) couple at about 0.02 V versus ferrocenium/ferrocene. Oxidation of 4 in CH(2)Cl(2) with silver triflate afforded an Ir(IV) species that exhibits an anisotropic electron paramagnetic resonance (EPR) signal in CH(2)Cl(2) glass at 4 K with g( parallel)=2.430 and g( perpendicular)=2.110. Protonation of 4 with HCl and p-toluenesulfonic acid (HOTs) afforded [{Ir(dtbpy)(CH(2)CMe(2)Ph)Cl}(2)(mu-Cl)(2)] (5) and [Ir(dtbpy)(CH(2)CMe(2)Ph)(OTs)(2)] (6), respectively. Reaction of 5 with Li[BEt(3)H] gave the cyclometalated complex [{Ir(dtbpy)(CH(2)CMe(2)C(6)H(4))}(2)(mu-Cl)(2)] (7). Reaction of 4 with tetracyanoethylene in refluxing toluene resulted in electrophilic substitution of the iridacycle by C(2)(CN)(3) with formation of [Ir(dtbpy)(CH(2)CMe(2)C(6)H(3){4-C(2)(CN)(3)})(2-C(6)H(4)CMe(3))] (8). Reaction of 4 with diethyl maleate in refluxing toluene gave the iridafuran compound [Ir(dtbpy)(CH(2)CMe(2)C(6)H(4)){kappa(2)(C,O)-C(CO(2)Et)CH(CO(2)Et)}] (9). Treatment of 9 with 2,6-dimethylphenyl isocyanide (xylNC) led to cleavage of the iridafuran ring and formation of [Ir(dtbpy)(CH(2)CMe(2)C(6)H(4)){C(CO(2)Et)CH(CO(2)Et)}(xylNC)] (10). Protonation of 9 with HBF(4) afforded the dinuclear neophyl complex [(Ir(dtbpy)(CH(2)CMe(2)Ph){kappa(2)(C,O)-C(CO(2)Et)CH(CO(2)Et)})(2)][BF(4)](2) (11). The solid-state structures of complexes 2-5 and 8-11 have been determined.

The novel lithium complexes [Li{N(SiMe3)C(R2)C(R1)(C5H4N-2)}]2 (R1 = H, R2 = But (1b); R1 = SiMe3, R2 = Ph (1c)) were prepared from the insertion of R2CN into [Li{C(SiMe3)(R1)(C5H4N-2)}]2. Similarly, Li{N(SiMe3)C(Ph)C(R)(C9H6N-2)} (R = H or SiMe3) was prepared from PhCN and Li{C(SiMe3)(R)(C9H6N-2)}. X-ray data are provided for 1b, 1c, and [Li{N(SiMe3)C(Ph)C(SiMe3)(C5H4N-2)}(Et2O)(PhCN)] (1c‘). Compounds 1b and 1c are dimers in the solid state, whereas 1c‘ is monomeric.

The lithium complexes [Li{N(SiMe3)C(R1)C(R2)(C5H4N-2)}]2 (1a, 2a, and 3a) were each treated with MCl4 to afford the racemic complexes [M{N(SiMe3)C(R1)C(R2)(C5H4N-2)}2Cl2] (M = Zr, R1 = Ph, R2 = H (1b); M = Zr, R1 = But, R2 = H (2b); M = Hf, R1 = But, R2 = H (2c); M = Zr, R1 = Ph, R2 = SiMe3 (3b)). Similarly, Li{N(SiMe3)C(Ph)C(R)(C9H6N-2)} (4a and 5a) afforded the racemic complexes [Zr{N(SiMe3)C(Ph)C(R)(C9H6N-2)}2Cl2] (R = H (4b); R = SiMe3 (5b)). X-ray structural analysis of 2b, 2c, and 3b revealed that these complexes have C 2 octahedral geometries with their chloride ligands in cis positions. Molecular orbital calculations on model systems of the bis{3-(2-pyridyl)-1-azaallyl}zirconium system [Zr(LL)2]2+ (LL = [N(H)C(H)C(H)(2-C5H4N]) demonstrate that (i) the frontier orbitals are similar to those of [Zr(η5-C5H5)2]2+ and (ii) the bis{3-(2-pyridyl)-1-azaallyl} ligand environment is more electron-donating, making the zirconium system less electrophilic. Conproportionation of ZrCl4 with [Zr{N(SiMe3)C(R1)C(R2)(C5H4N-2)}2Cl2] or [Zr{N(SiMe3)C(Ph)C(SiMe3)(C9H6N-2)}2Cl2] afforded the mono(1-azaallyl)zirconium complexes Zr{N(SiMe3)C(R1)C(R2)(C5H4N-2)}Cl3 (R1 = But, R2 = H (2d); R1 = Ph, R2 = SiMe3 (3d)) and Zr{N(SiMe3)C(Ph)C(SiMe3)(C9H6N-2)}Cl3 (5d), respectively. When activated with methylaluminoxane (MAO), these compounds were highly active in ethylene polymerization. Compound 3d also showed modest activity in the polymerization of 1-hexene and the copolymerization of ethylene and 1-hexene.