Sulfur-nitrogen-bonded metal chelates. 18. 1,3-Dipolar cycloadditions to coordinated azide in nickel(II) complexes of the types [Ni(S-N-N)(N3)] and [S-N-N)Ni(N3)Ni(N-N-S)](ClO4)

Abstract

Sulfur-Nitrogen-Bonded Metal Chelates. 18. 1,3-Dipolar Cycloadditions to Coordinated Azide in Nickel(II) Complexes of the Types [Ni(S N N)(N3)] and [(S'l<~N)Ni(N3)Ni(POrS)](C104)

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…[83,85] Again the overall-order of reactivity of the nitriles RCN with R = C 6 H 4 NO 2 -(4) Ͼ C 6 H 4 Cl-(4) Ͼ Ph Ͼ Me, and the linear plot log k obsd /σ p for the reactions with the aromatic nitriles proved to be in line with the well-established picture. Variation of the tridentate S,N,N-chelating ligand 1 caused the reaction rates to significantly decrease in the order R' = H Ͼ Me Ͼ Et which at first -contradictory to the results with cis-[Pt(N 3 ) 2 (PPh n Bu n 3-n ) 2 ]/RCN [142,171] -had been associated with the electron-releasing power of the terminal nitrogen atom, [85] but was re-interpreted as a steric effect in a later communication. [86] Moreover, from the moderate ΔH ‡ and large negative ΔS ‡ values it was deduced that these cycloaddition reactions are concerted, just like their organic congeners.…”

“…[55] In several papers on 1,3-dipolar cycloadditions of azido complexes of nickel(II) and palladium(II), Paul and coworkers have demonstrated the advantage of a coordination sphere essentially taken up by a tridentate {R 2 }N,N,S-chelating ligand (1) with just one open site for N 3 . [83,[85][86][87] Exactly www.zaac.wiley-vch.de REVIEW the same idea, viz. to activate azide by nickel(II), platinum(II) and copper(II) centres bearing a tri-hapto N,N,O-aminoiminophenolato ligand (2), turns up again in a more recent publication by Pombeiro and in a brandnew paper by Mukhopadhyay.…”

“…Much in contrast, the kinetics of the cycloaddition reactions of the monoazido complexes Ni(N 3 )(S,N,N{R' 2 }) (R' = H, Me, Et), [(S,N,N{H 2 })Ni(μ 1,3 -N 3 )Ni(S,N,N{H 2 })]ClO 4 and Pd(N 3 ) (S,N,N{R' 2 }) (κ 3 (S,N,N{R' 2 } = 1; R' = H, Me, Et)) with nitriles (RCN) have thoroughly been investigated including temperature and solvent effects. [85] Square-planar nickel(II) complexes were found to be more reactive than the corresponding palladium(II) species which has been explained by the greater charge density on Ni II and its polarizing effect on the azide. [83,85] Again the overall-order of reactivity of the nitriles RCN with R = C 6 H 4 NO 2 -(4) Ͼ C 6 H 4 Cl-(4) Ͼ Ph Ͼ Me, and the linear plot log k obsd /σ p for the reactions with the aromatic nitriles proved to be in line with the well-established picture.…”

“…[85] Square-planar nickel(II) complexes were found to be more reactive than the corresponding palladium(II) species which has been explained by the greater charge density on Ni II and its polarizing effect on the azide. [83,85] Again the overall-order of reactivity of the nitriles RCN with R = C 6 H 4 NO 2 -(4) Ͼ C 6 H 4 Cl-(4) Ͼ Ph Ͼ Me, and the linear plot log k obsd /σ p for the reactions with the aromatic nitriles proved to be in line with the well-established picture. Variation of the tridentate S,N,N-chelating ligand 1 caused the reaction rates to significantly decrease in the order R' = H Ͼ Me Ͼ Et which at first -contradictory to the results with cis-[Pt(N 3 ) 2 (PPh n Bu n 3-n ) 2 ]/RCN [142,171] -had been associated with the electron-releasing power of the terminal nitrogen atom, [85] but was re-interpreted as a steric effect in a later communication.…”

“…[24b,c,e,g, 83,[85][86][87] Another family of azide-containing chelate complexes that has been subjected to [3+2]-cycloadditions with nitriles consists in the pentacoordinate azido(porphinato)iron(III) and -manganese(III), and the hexacoordinate azido(triphenylphosphine)(Salphen)-and -(Salen)cobalt(III) systems (cf. 4-6 and Table 1).…”