Expanding Heteroscorpionates. Facile Synthesis of New Hybrid Scorpionate/Cyclopentadienyl Ligands and Their Lithium and Group 4 Metal Compounds: A Combined Experimental and Density Functional Theory Study

The preparation of new hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives [Li(bpzcp)(THF)] (1) [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and [Li(bpztcp)(THF)] (2) [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl] or as a mixture of the two scorpionate/cyclopentadiene regioisomers (bpzpcpH) 1-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethyl]-1,3-cyclopentadiene (3a) and 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethyl]-1,3-cyclopentadiene (3b) has been carried out by reaction of bis(3,5-dimethylpyrazol-1-yl)methane (bdmpzm) with BunLi and 6,6-diphenylfulvene, 6-tert-butylfulvene, or 6-phenylfulvene, respectively. However, when this insertion reaction was carried out with 6,6-dimethylfulvene, the compound [Li(isoprcp)(bdmpzm)(THF)] (4) [isoprcp = isopropenylcyclopentadienyl] was obtained. Compounds 1 and 2 reacted with [TiCl4(THF)2] or [MCl4] (M = Zr, Hf) to give the complexes [MCl3(bpzcp)] (M = Ti, 5; Zr, 6; Hf, 7) and [MCl3(bpztcp)] (M = Ti, 8; Zr, 9; Hf, 10). Similar reactions do not take place with the mixture of the two isomers 3a and 3b. However, when a THF solution of 3a−3b and [MCl4] (M = Zr, Hf) was heated under reflux, the complexes [MCl3(bpzpcp)] (M = Zr, 11; Hf, 12) [bpzpcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] were obtained. In addition, alkyl complexes [ZrClMe2(bpztcp)] (13) and [ZrMe3(bpztcp)] (14) were also prepared. The structures of these complexes have been determined by spectroscopic and DFT methods, and in addition, the X-ray crystal structures of 1, 2, 3b, and 6 were also established.