1-Methylimidazolin-2-yl functionalized cyclopentadienyl complexes of titanium and zirconium. Crystal structure of {[η5:η1-κN-C5H4CPh2CH2-(1-Me–C3H4N2)]ZrCl2}2(μ-Cl)2

The novel bidentate ligand, C5H4CPh2CH2-(1-Me–C3H4N2) (3), has been prepared and characterized as its lithium salt LiC5H4CPh2CH2-(1-Me–C3H4N2) (3–Li). Cyclopentadiene HC5H4CPh2CH2-(1-Me–C3H4N2) (3–H) has been obtained from 6,6-diphenylfulvene and 1,2-dimethylimidazoline (1). In THF-d8 solution in the presence of 1, (1-methylimidazoline-2-yl)methyllithium (2) has been proved to undergo gradual conversion into a dilithium derivative of N1-methyl-N2-[(1E,2E)-1-methyl-2-(1-methylimidazolidine-2-idene)ethylidene]ethane-1,2-diamine (2a). In a solution, cyclopentadiene 3–H has been shown to undergo isomerization into 3-{N-[2-(N-methylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (4) and, further, into a mixture of 4 and two rotameric 3-[N-(2-aminoethyl)-N-methylamino]-1,1-diphenyl-1,2-dihydropentalenes (5a) and (5b). Treatment of the lithium salt 3–Li with Me3SiCl has lead to 3-{N-[2-(N-trimethylsilylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (6) as the dominant component in the reaction mixture. In the latter case the expected Me3Si–C5H4CPh2CH2-(1-Me–C3H4N2) (3–Si) was not observed. Stannylation of 3–Li with 1 equiv. of Me3SnCl has resulted in formation of a mixture of Me3Sn–C5H4CPh2CH2-(1-Me–C3H4N2) (3–Sn), (Me3Sn)2-C5H3CPh2CH2-(1-Me–C3H4N2) (3–Sn2), and cyclopentadiene 3–H in a ca. 2:1:1 molar ratio. Monocyclopentadienyl complexes {[η5:η1-κN-C5H4CPh2CH2-(1-Me–C3H4N2)]MCl3 (M = Ti (7), Zr (8)) have been prepared starting from the organotin and organolithium compounds 3–Sn and 3–Li, respectively. The dynamic behavior of complexes 7 and 8 has been investigated by means of variable-temperature NMR spectroscopy in solutions. The molecular structures of the dihydropentalene 4, binuclear complex {[η5:η1-κN-C5H4CPh2CH2-(1-Me–C3H4N2)]ZrCl2}2(μ-Cl)28, and a coordination dimer of the dilithium salt 2a have been established by X-ray diffraction analysis. In the crystal structure of the 2a-dimer, the shortest known Li–Li contact has been found.