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New heteroscorpionate ligands in the form of the lithium derivatives are prepared to enable the reaction with [Bu.sup.eta]Li and carbodiimide derivatives. It is demonstrated that it is possible to isolate alternative compounds from solutions exposed to air.

The synthesis of the ligands 2,4,6-tris(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-TPzT), 2,4,6(4-bromopyrazol-1-yl)-1,3,5-triazine (Br-TPzT) and 2-methoxy-4,6-bis(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-BPzTOMe) was described. In addition, the reactions of the ligands with some palladium analogues were investigated. Experimental results revealed two simultaneous fluxional processes with different energy barriers, and this difference is attributed to the Pd-N bond strength.

The preparation and spectroscopic characterization of substituted niobocene trihydrides of the type Nb(C5H3RR')2H3 where R=R' when R'=H, R=H when R'=SiMe3 and R=R' when R'=SiMe3 were performed. Likewise, the influence on exchange coupling and the adducts formed upon addition of Lewis acidic copper, silver and gold cations of the type (Cu(MeCN)4)PF6, AgBF4 and Auu(THT)PF6, were also investigated.

Hydrolysis study of AgPF6 in CH2Cl2, chloroform and benzene reveal the involvement of silver cation in the reaction. 19F and 31P NMR spectra are employed to study the intermediates involved in the hydrolysis of AgPF6 by CD2Cl2. Acetone, acetonitrile and tetrahydrofuran solvents do not give the hydrolysis reaction. The coordinating ability of silver cation with solvent is vital in controlling the promotion of hydrolysis. The silver center promotes the cationic activation of water molecule.

A one step synthesis of an enantiopure scorpionate ligand through a highly diastereoselective nucleophilic 1,2-addition of an organolithium reagent is described.

The application of hybrid scorpionate/cyclopentadienyl ligands as catalysis in the synthesis of neutral scandium and yttrium halide and alkoxide complexes is described. The results showed the complexes as active styrene polymerization catalysts after activation with excess MAO, generating atactic polystyrenes with low molecular weights and narrow molecular weight distributions.

The synthesis and characterization of new classes of neutral and anionic scandium and yttrium complexes containing heteroscorpionate ligands along with halide and phenanthroline as ancillary ligands is presented. The reactivity of some of these complexes with alcohols and amides gives new alkoxide and amide complexes.

The niobium-gold complex prepared from a niobium trihydride exhibits higher exchange coupling properties than its starting compound. X-ray studies show that one of the two bridging hydrides between niobiuim and gold is closer to the terminal hydride. NMR spectra confirm this proximity and reveal the temperature dependence of the couplings. NMR spectra reveal the presence of linear arrangement of Nb, Au and Nb atoms in the metal core, with an Nb-Au separation of 2.965 angstroms.

The spectroscopic properties of a series of new adducts of substituted niobiocene trihydrides with Cu1+ and Ag1+ are investigated. These complexes include ((Cp2NbH3)2Cu)PF6, ((Cp'2NbH3)2Cu)PF6, ((Cp''2NbH3)2Cu)PF6, ((Cp'NbH3)2Ag)BF4 and ((Cp''2NbH3)Ag)BF4. Results show that exchange couplings in trihydrides are slightly affected by Lewis acid coordination. Moreover, the non-existence of exchange couplings in the copper adduct of Cp2NdH3 indicates that niobium does not cause the broad lines observed for the hydrides.

Reaction of hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives [Li(bpzcp)(THF)] [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl], [Li(bpztcp)(THF)] [bpztcp = 2,2-bis(3,5- dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl], and the in situ-generated "Li(bpzpcp)" [bpzpcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] with MCl3(THF)3 afforded the group 3 halide compounds [MCl2(bpzcp)(THF)] (M = Sc, 1; Y, 2), [MCl2(bpztcp)(THF)] (M = Sc, 3; Y, 4), and [MCl2(bpzpcp)(THF)] (M = Sc, 5; Y, 6). The H20 adduct of 4, [YCl2(bpztcp)(H2O)] (7), was formed when a solution of 4 was allowed to stand at room temperature in the presence of moisture. Complexes 1-7 adopt a pseudo-octahedral structure with heteroscorpionate ligands κ²-NNη5-Cp coordinated to the metal through the cyclopentadienyl group and two imino nitrogens of pyrazole rings. The alkyl heteroscorpionate scandium and yttrium complexes recently reported by our group, [M(CH2SiMe3)2(bpzcp)], react with 2,6-dimethylphenol and 3,5-dimethylphenol to give the bis(aryloxide) derivatives [M(OAr)2(bpzcp)] (M Sc, OAr = 2,6-dimethylphenoxide, 8; M = Y, OAr = 2,6-dimethylphenoxide, 9; M = Y, OAr = 3,5-dimethylphenoxide, 10). Complex 9 underwent an interesting hydrolysis process to give the tetranuclear complex [{Y(bpzcp)}(u-OH)2(μ3-OH){Y(OAr)2}]2 (11). Variable-temperature ¹H NMR experiments on 9 and 10 revealed a rapid fluxional exchange between coordinated and noncoordinated pyrazolyl rings, producing interconversion between the two enantiomers in which the scorpionate ligand can be coordinated in a κ¹-Nη5-Cp form. The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures of 2, 7, and 11 were also established. Complexes 1 and 2 are active olef in polymerization catalysts after activation with methylaluminoxane. These compounds gave atactic polystyrenes with narrow molecular weight distribution (Mn/Mw 1.26-1.91) and with low molecular weights. [ABSTRACT FROM AUTHOR]

The ligands 2,4,6-tris(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-TPzT), 2,4,6-tris(4-bromopyrazol-1-yl)-1,3,5-triazine (Br-TPzT), and 2-methoxy-4,6-bis(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-BPzTOMe) have been synthesized and their reactions with some palladium derivatives explored. The palladium fragment [Pd(eta(3)-2-Me-C(3)H(4))(S)(2)](+), S = acetone, reacts in acetone with Me-TPzT or Br-TPzT in a 3:1 molar ratio to generate new complexes in which two allylpalladium fragments are present and the TPzT ligands have been partially hydrolyzed: [{Pd(eta(3)-C(4)H(7))}(2)(X-BPzTO)]A, X-BPzTO = 4,6-bis[4-methyl(or bromo)pyrazol-1-yl]-1,3,5-triazin-2-olate (X = Me, A = BF(4), 1; A = PF(6), 2; A = CF(3)SO(3), 3; A = p-MeC(6)H(4)SO(3), 4; X = Br, A = CF(3)SO(3), 5). When the ligand Me-BPzTOMe is made to react with only 1 equiv of the palladium solvate, compound 6, [Pd(eta(3)-2-Me-C(3)H(4))(Me-BPzTOMe)]CF(3)SO(3), is isolated. Reaction of 6 with another 1 equiv of the palladium derivative leads to 3. The intermediate 7, [{Pd(eta(3)-2-Me-C(3)H(4))}(2)(Me-BPzTOMe)]CF(3)SO(3), has been isolated as an almost pure compound. The reaction of Me-BPzTOMe with 1 equiv of [Pd(C(6)F(5))(2)(cod)] (cod = 1,5-cyclooctadiene) leads to the complex [Pd(C(6)F(5))(2)(Me-BPzTOMe)], 8. Attention has been focused on the dynamic behavior, related with metallotropic phenomena, of the new complexes. (1)H NMR variable-temperature studies of complexes 1, 6, and 8 have been carried out. For 8, only one static species is observed, while, for 1 and 6, two isomers are detected at low temperature. Different DeltaG(c)() activation energies at the coalescence temperature have been determined and are ascribed to processes implying Pd-N bond ruptures. For 6, two different barriers are detected, corresponding to Pd-N(triazine) or Pd-N(pyrazole) bond ruptures. From the DeltaG(c)() data, it is concluded that the main driving force of the hydrolysis process is the formation of a better coordinating ligand. The molecular structure of 4 has been determined by X-ray diffraction. The meso isomer, in which the two C-Me axes of the allylic groups are oriented in the same direction, is found in the solid state.