trans,trans,trans-(1,5,9 Cyclododecatriene)nickel(0) a organonickel compound with the formula NiC<sub>12</sub>H<sub>18</sub>, better known as t-Ni(cdt). It is a 16-electron coordination complex featuring trigonal planar nickel (0) bound to the three alkene groups in the cyclododecatriene ligand. X-ray structural analysis demonstrates that the three olefins adopt a propeller-like arrangement around the nickel atom center, making the structure chiral. This extremely air-sensitive deep red solid was the first discovered Ni(0)-olefin complex.
The complex is prepared by reduction of anhydrous nickel(II) acetylacetonate in ether in the presence of the triolefin:
ÃÂ-Donating ligands such as carbon monoxide, isonitriles, phosphines, and hydrides can readily add onto t-Ni(cdt) to furnish tetrahedral 18-electron nickel complexes. It has been demonstrated that this fourth coordination site can be leveraged to separate the t-Ni(cdt) enantiomers with recrystallization of diastereomeric 18-electron t-Ni(cdt)L* complexes (where L* = optically active dimethylmenthylphosphine ligand).
The all-trans-(cdt) ligand has been shown to be easily displaced with olefins such as trans-cyclooctene, ethylene, all-cis-(cdt), norbornene, to give the corresponding colorless 16-electron Ni(0)-olefin complexes with coplanar geometry. Ni(cod)<sub>2</sub> can also be easily prepared from Ni(cdt).
Recently, it was demonstrated that t-Ni(cdt) can be used to synthesize unique air-stable 16-electron Ni(0)âÂÂolefin complexes, such as Ni(<sup>F</sup>stb)<sub>3</sub> and Ni(<sup>4-tBu</sup>stb)<sub>3</sub> using (E)-stilbene ligands.