Synthesis and catalytic properties of oxalic amidinato complexes

The oxalic amidine compounds C6H5N=C((NHBu)-Bu-t)-C((NHBu)-Bu-t)=NC6H5 1 and C6H5N=C{N(Bu-t)(SiMe3)}-C{N(Bu-t)(SiMe3)}=NC6H5 2 are described. The compound [(C6H5N)C((NHBu)-Bu-t)-C((NHBu)-Bu-t)(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)(2)Cl-3(py)] or [Zr{N(SiMe3)(2)}(3)Cl] gives the bimetallic complexes [M(NMe2)(3)(C6H5N)C((NBu)-Bu-t)-](2) (M = Zr (4) or M = Ti (5)) and the mono-amidinato complexes [Ta(NEt2)Cl-3{(C6H5N)C((NBu)-Bu-t)C((HNBu)-Bu-t)(NC6H5)}] 6* and [Zr{N(SiMe3)(2)}(2)Cl{(C6H5N)C((NBu)-Bu-t)C((HNBu)-Bu-t)(NC6H5)}] 7* respectively: * indicates the crystal structure has been determined. The activity toward ethylene polymerisation has been investigated for compounds 4, 5 and 7.