Synthesis and catalytic properties of oxalic amidinato complexes

Abstract

The oxalic amidine compounds C₆H₅NC(NH^tBu)–C(NH^tBu)=NC₆H₅1 and C₆H₅NC{N(^tBu)(SiMe₃)}–C{N(^tBu)(SiMe₃)}=NC₆H₅2 are described. The compound [(C₆H₅N)C(NH^tBu)–C(NH^tBu)(NHC₆H₅)][Br] 3* has been isolated from the reaction between 1 and [NiBr₂(DME)]. Treatment of 1 with M(NMe₂)₄ (M = Zr or Ti), [Ta(NEt₂)₂Cl₃(py)] or [Zr{N(SiMe₃)₂}₃Cl] gives the bimetallic complexes [M(NMe₂)₃(C₆H₅N)C(N^tBu)–]₂ (M = Zr (4) or M = Ti (5)) and the mono-amidinato complexes [Ta(NEt₂)Cl₃{(C₆H₅N)C(N^tBu)C(HN^tBu)(NC₆H₅)}] 6* and [Zr{N(SiMe₃)₂}₂Cl{(C₆H₅N)C(N^tBu)C(HN^tBu)(NC₆H₅)}] 7* respectively: * indicates the crystal structure has been determined. The activity toward ethylene polymerisation has been investigated for compounds 4, 5 and 7.