Synthesis and characterisation of κ²-N,O-oxazoline-enolate complexes of nickel(ii): explorations in coordination chemistry and metal-mediated polymerisation

Abstract

The synthesis and characterisation (UV-Vis, IR, X-ray diffraction, etc.) of a series of Ni(II) complexes derived from both known and novel 2-acylmethyl-2-oxazolines (2a-g: i.e., (Z)-1-R-2-(4,4 0 -dimethyl-2 0 -oxazolin-These Ni materials (3a-g) represent the first group 10 metal complexes of this ligand class. All derivativesen-1-ate formed via proton loss from 2. The air-and moisture-stable metal complexes feature a less typical distorted seesaw-shaped disposition of binding atoms around the metal centre for six structurally characterised (X-ray) examples. Preliminary investigations indicate that 3a (R ¼ -Ph) is a useful catalysts for olefin polymerisation in the presence of alkylaluminum reagents. Scheme 1 Azole heterocycles: 1,3-oxazole (top, left); 1,3-benzoxazole (top, middle); 4,5-dihydro-1,3-oxazole (i.e., 2-oxazoline: top, right); 2-acylmethyl-2-oxazoline (A: bottom; enol tautomer shown).(2) { Reduced yields were noted employing [Ni(OH 2 ) 6 ](NO 3 ) 2 or [Ni(OH 2 ) 6 ]Cl 2 .This journal is a Polymerisation conditions: 1 h at 60 C; 20 mmol of 3a in 2 mL of C 7 H 8 ; 3 mL (2.7 g; 0.026 mol) of styrene in 7 mL C 7 H 8 . This journal is

Nickel(ii)-methyl complexes adopting unusual seesaw geometries

“…[19][20][21] Other examples include those by Gossage and Baruah where homoleptic complexes of Ni(II) were synthesized with bulky propan-2-ylidene and oxazoline substituents that prevent planarization of the Ni(II) coordination environment. 14,22 Another recent example of a seesaw geometry at a Ni(II) center involves a diisopropylpyrazole-substituted carbazole ligand to enforce steric crowding of the square plane. 13 Finally, an example of a ligand-constrained geometry around a Ni(II) center can be seen in a complex bound to a triphosphacyclododecane ligand.…”

Divalent Cobalt and Copper Coordination Complexes of κ2-N, O-Derivatives of (Z)-1-R-2-(2’-oxazolin-2’-yl)-eth-1-en-1-ates: Structure and Reactivity Patterns

“…Previous work on Ni(II) systems had revealed that coordination is facilitated by the addition of base to a Ni(II) salt; hence, we employed a similar tactic here. [45] Thus, treatment of solutions (EtOH / MeOH) of cobaltous chloride or nitrate with 1a -1c, in the presence of excess of NEt3, were found to be optimal to give the corresponding Co(1 -H)2 complexes (2a -2c: Scheme 2 and Experimental Section).…”

Divalent cobalt and copper coordination complexes of κ2-N, O-derivatives of (Z)-1-R-2-(2′-oxazolin-2′-yl)-eth-1-en-1-ates: Structure and reactivity patterns

“…Such a situation we have already probed in the chemistry of four-coordinate Ni(II). [45] These Group 10 compounds likewise reveal uncommon bonding modes at the Ni centres. In addition, these materials have been shown to be useful polymerization catalysts when employing alkyl Al reagents as co-promoters.…”