[N-Alkyl-(2-pyridyl)methanimine]copper(I) Complexes: Characterisation and Application as Catalysts for Atom-Transfer Polymerisation

Abstract

The synthesis and characterisation of a series of novel bis(imine)copper(I) complexes and their use in atom‐transfer polymerisation of methyl methacrylate is described. Several N‐alkyl‐(2‐pyridyl)methanimines (alkyl = n‐butyl, isobutyl, sec‐butyl, n‐propyl) and N‐(n‐propyl)‐1‐(2‐pyridyl)ethanimine as ligands have been fully characterised. Three bis[N‐alkyl‐(2‐pyridyl)methanimine]copper(I) complexes, [Cu{(C5H4N)CH=N(iBu)}2][BF4], [Cu{(C5H4N)C(CH3)=N(nPr)}2][PF6], and [Cu{(C5H4N)CH=N(sBu)}2][BF4] have been structurally characterised; all having a distorted tetrahedral arrangement of co‐ordinating nitrogen atoms surrounding the metal centre. All of the catalysts were found to be effective atom‐transfer polymerisation catalysts for the polymerisation of MMA in hydrocarbon solution. However, it was discovered that the performance of the catalysts containing n‐alkyl substituents was superior to those containing branched alkyl substituents. The presence of branching in the alkyl substituent results in a reduction of reaction rate and a corresponding broadening of the polydispersity index.

Synthesis, Characterization, and Catalytic Application of Mononuclear and Dendritic Cationic CuI Iminopyridine‐Ligated Complexes in Aryl Iodide Hydroxylation

“…For complex C2 , τ 4 = 0.67, which correlates to a see‐saw geometry about the metal center (for see‐saw geometry, τ 4 = 0.64). Similarly, calculating τ 4 for analogous [L 2 Cu] + X – complexes reported by Haddleton et al we obtained values of 0.72 and 0.69.…”

“…This is evidenced by the N1–Cu1–N1′ and N1–Cu1–N2′ bond angles of 118.09 and 114.30°, respectively. The Cu1–N1 and Cu1–N2 bond lengths of 2.080(1) and 1.985(1) Å, respectively, are within the reported range for complexes of the type [L 2 Cu] + X – , . Houser and co‐workers have developed a simple geometric index parameter, τ 4 , for four‐coordinate complexes .…”

“…The 1 H and 13 C{ 1 H} NMR spectra show the imine resonance as a singlet in the range δ = 8.53–9.19 and 161.21–162.32 ppm, respectively, downfield‐shifted in comparison with the free ligand. Both analytical techniques confirmed the coordination of the metal to the ligand , …”

“…1 H NMR spectroscopic analysis confirmed imine formation, observed as a singlet resonance in the range δ = 8.29–8.55 ppm. The mononuclear ( C1 – C4 ) and dendritic ( DC1 – DC8 ) cationic Cu I N ‐propyliminopyridine‐ligated complexes were prepared by treating the mono‐ or multifunctional ligands with tetrakis(acetonitrile)copper(I) tetrafluoroborate in a 2:1, 1:2, or 1:4 ratio (Scheme ) . The complexes were isolated as microcrystalline ( C1 – C4 ) or amorphous solids ( DC1 – DC8 ) in good‐to‐excellent yields (78–94 %).…”

A density functional theory computational study of the role of ligand on the stability of CuI and CuII species associated with ATRP and SET‐LRP

“…Already mentioned is ammonia, used as a nonchelating ligand model system. To help understand results from studies on SET‐LRP, we have chosen to test tris(2‐dimethylaminoethyl)amine (Me 6 ‐TREN), tris(2‐aminoethyl)amine (TREN), 2,2′‐bipyridine (BPy), and N ‐ n ‐propyl‐2‐pyridiyl‐methanimine (Pr‐PMI, “Haddleton's Ligand”) 14, 15. To allow access to structures that are biased toward square planar and square pyramidal structures, we have included 1,4,8,11‐tetraazacyclotetradecane (CYCLAM) and N,N,N ′, N ′‐tetramethylethyldiamine (TMEDA), respectively.…”