Popis: |
Interaction of [NbCl 5 ] with the diphenol 2,2′-CH 3 CH[4,6-(Bu t ) 2 C 6 H 2 OH] 2 (LH 2 ) affords, after work-up, the red crystalline complex [NbCl(NCMe)L 2 ] ( 1 ). Under similar conditions, [NbOCl 3 ] and the sulfur-bridged diphenol 2,2′-S[4,6-(Bu t ) 2 C 6 H 2 OH] 2 (L S H 2 ) afford the orange complex [NbCl(L S ) 2 ] ( 2 ). Crystal structure determinations of 1 · 2MeCN and 2 reveal monomeric 6- and 7-coordinate complexes, respectively. The polymerization behaviour of 1 and 2 towards ethylene, in the presence of alkylaluminium co-catalysts has been examined and has been compared with that of the known niobium aryloxides [Nb(Me–L 2 )Cl 2 ] 2 ( 3 ), {Nb[(Bu t -L 2 )H] 2 Cl(NCMe)} ( 4 ) and [Nb(Bu t -L 2 )Cl 2 ] ( 5 ), derived from the linear-linked aryloxide trimers 2,6-bis(4,6-dimethylsalicyl)-4- tert -butylphenol [(Me–L 2 )H 3 ] and 2,6-bis(4-methyl-6- tert -butylsalicyl)-4- tert -butylphenol [(Bu t -L 2 )H 3 ]. The crystal structure of the acetonitrile solvate of 3 · 4MeCN, is also reported. |