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 Bu n Li 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( isopr cp)(bdmpzm)(THF)] ( 4 ) [ isopr cp = isopropenylcyclopentadienyl] was obtained. Compounds 1 and 2 reacted with [TiCl 4 (THF) 2 ] or [MCl 4 ] (M = Zr, Hf) to give the complexes [MCl 3 (bpzcp)] (M = Ti, 5; Zr, 6; Hf, 7 ) and [MCl 3 (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 [MCl 4 ] (M = Zr, Hf) was heated under reflux, the complexes [MCl 3 (bpzpcp)] (M = Zr, 11; Hf, 12 ) [bpzpcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] were obtained. In addition, alkyl complexes [ZrClMe 2 (bpztcp)] ( 13 ) and [ZrMe 3 (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.