A spectroscopic and magnetic study of some metal complexes of malonaldehydedianil

The Chemistry of β-Diketiminatometal Complexes

“…The field owes its genesis in the mid to late 1960s to classical coordination chemistry studies of homoleptic M(II) β-diketiminates (M = Co, Ni, Cu); the emphasis was on their synthesis, spectra, magnetism, and structures. ,8a− …”

“…In a 1966 review of the stereochemistry of bis(chelate)metal(II) complexes, a short section was devoted to the then available data on bis(β-iminate)s; these were then restricted to the homoleptic M(II) complexes of Co, Ni, and Cu . The first of these was [Cu{(N(Ph)C(H)) 2 CH} 2 ]. , Others, studied during 1964−1968, were of formula [M{(N(R 1 )C(R‘)) 2 CH} 2 ] (R 1 = H, Me, Et, CH 2 Ph, Ph, C 6 H 4 Me-3, C 6 H 4 Me-4; R‘ = H, Me). 8a,− ,,,− The interest then was to establish their structures, in most cases by measurements of magnetic moments, ligand field spectra, and isotropic 1 H NMR spectral shifts. Of such complexes, only those with R 1 = H were judged to have a planar four-coordinate metal environment, the others being tetrahedral (Co) or distorted tetrahedral.…”

“…The syntheses of the above homoleptic M(II) complexes were unexceptional (but see eq 5 9,10 and Scheme 44 ) and involved the reaction of the β-diketimine or its hydrochloride with [NEt 4 ][MX 4 ] (X = Cl or Br 8a ) or M(OAc) 2 in the presence of a base such as NaOMe or aqueous ammonia. 8a,− ,− Alternatively, the reaction between [LiL] 2 and anhydrous MCl 2 (L = [{N(R)C(Ph)} 2 CH] - ) or [PdCl 2 (cod)] in diethyl ether yielded [M{(N(R)C(Ph)) 2 CH} 2 ] (M = Co, , Ni, Cu, , Pd 45 ). Treatment of [LiL] 2 with hydrated CoSO 4 gave [CoL‘ 2 ], , and the correspond-ing Ni and Cu complexes were obtained from the appropriate MCl 2 in the presence of a trace of water (L‘ = [{N(H)C(Ph)} 2 CH]). , Other homoleptic M(II) β-diiminates reported were [Co{N(R 1 )C(R‘ ‘)C(R‘)C(R‘ ‘‘)NR 1 } 2 ] [R 1 = Ph = R‘ ‘, R‘ = H = R‘ ‘‘; R 1 = C 6 H 4 X-4 (X = Me, OMe, Br), R‘ ‘ = Ph, R‘ = H = R‘ ‘‘; R 1 = C 6 H 4 Br-4 = R‘ ‘, R‘ = H = R‘ ‘‘] and close Ni(II) and Cu(II) analogues 48b…”

“…2 The first of these was [Cu{(N(Ph)C(H)) 2 CH} 2 ]. 12,13 Others, studied during 1964-1968, were of formula [M-{(N(R 1 )C(R′)) 2 CH} 2 ] (R 1 ) H, Me, Et, CH 2 Ph, Ph, C 6 H 4 Me-3, C 6 H 4 Me-4; R′ ) H, Me). 8a,11-13,16,17,92-94 The interest then was to establish their structures, in most cases by measurements of magnetic moments, ligand field spectra, and isotropic 1 H NMR spectral shifts.…”

“…Early work on β-diiminates of zinc concerned the synthesis (from HL′ and ZnCl 2 , in the presence of a base) and spectra of the complexes ZnL′ 2 (L′ ) [N(Et)C(H)C(H)C(Me)NEt], 10 [{N(Ph)C(H)} 2 CH], 12 and [{N(R 1 )C(H)} 2 CPh] (R 1 ) C 6 H 4 Cl-4, C 6 H 4 Me-4) 94 ). Revival of interest in zinc β-diketiminates has largely been triggered by the disclosure that some are living single-site catalysts not only for the ring-opening polymerization of lactide (LA) 33,107,108 (see Scheme 19; 33 for a review of this topic using these and other catalysts, see ref 70) but also for the copolymerization of cyclohexene oxide (CHO) and carbon dioxide 35,109,110 [see Scheme 20, illustrated for a metal alkoxide, such as [Zn(L)O i Pr].…”