Synthesis, characterization, and reactivity of new types of constrained geometry group 4 metal complexes derived from picolyl-substituted dicarbollide ligand systems |
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Authors: | Jong-Dae Lee Ki-Chul Son Minserk Cheong Sang Ook Kang |
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Institution: | a Department of Chemistry, Chosun University, 375 Seosuk, Dong-gu, Gwangju 501-759, Republic of Korea b Department of Chemistry, Korea University, 208 Seochang, Chochiwon, Chung-nam 339-700, Republic of Korea c Department of Chemistry and Research Institute for Basic Sciences, Kyung Hee University, Seoul 130-701, Republic of Korea |
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Abstract: | The syntheses of group 4 metal complexes containing the picolyldicarbollyl ligand DcabPyH nido-7-HNC5H4(CH2)-8-R-7,8-C2B9H10] (2) are reported. New types of constrained geometry group 4 metal complexes (DcabPy)MCl2, {(η5-RC2B9H9)(CH2)(η1-NC5H4)}MCl2] (M = Ti, 3; Zr, 4; R = H, a; Me, b), were prepared by the reaction of 2 with M(NMe2)2Cl2 (M = Ti, Zr). The reaction of 2 with M(NMe2)4 in toluene afforded (DcabPy)M(NMe2)2, {(η5-RC2B9H9)(CH2)(η1-NC5H4)}M(NMe2)2] (M = Ti, 5; Zr, 6; R = H, a; Me, b), which readily reacted with Me3SiCl to yield the corresponding chloride complexes (DcabPy)MCl2 (M = Ti, 3; Zr, 4; R = H, a; Me, b). The structures of the diamido complexes (DcabPy)M(NMe2)2 (M = Ti, 5; Zr, 6) were established by X-ray diffraction studies of 5a, 5b, and 6a, which verified an η5:η1-bonding mode derived from the dicarbollylamino ligand. Related constrained geometry catalyst CGC-type alkoxy titanium complexes, (DcabPy)Ti(OiPr)2 (7), were synthesized by the reaction of 2 with Ti(OiPr)4. Sterically less demanding phenols such as 2-Me-C6H4OH replaced the coordinated amido ligands on (DcabPy)Ti(NMe2)2 (5a) to yield aryloxy stabilized CGC complexes (DcabPy)Ti(OPhMe)2(PhMe = 2- Me-C6H4, 8). NMR spectral data suggested that an intramolecular Ti-N coordination was intact in solution, resulting in a stable piano-stool structure with two aryloxy ligands residing in two of the leg positions. The aryloxy coordinations were further confirmed by single crystal X-ray diffraction studies on complexes (DcabPy)Ti(OPhMe)2 (8). |
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Keywords: | Pyridylmethylamino dicarbollyl ligand Group 4 metal complexes Constrained geometry catalysts Olefin polymerization Intramolecularly coordination Zwitterionic compound |
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