Transition-metal–carbon bonds. Part 45. Attempts to cyclopalladate some aliphatic oximes, NN-dimethylhydrazones, ketazines, and oxime O-allyl ethers. Crystal structures of [Pd2{CH2C(CH3)2C(NOH)CH3}2Cl2] and [Pd{CH2C(NNMe2)C(CH3)3}(acac)]

Abstract

E-Methyl t-butyl ketoxime, with sodium acetate and Na₂[PdCl₄] in methanol, cyclopalladates regiospecifically on a t-butyl methyl to give the chloride-bridged complex [Pd₂{CH₂C(CH₃)₂C(NOH)CH₃}₂Cl₂](1a), the crystal structure of which has been determined (see below). The corresponding bromide and iodide complexes have been made, as have several mononuclear species by bridge-splitting reactions, e.g. of type [[graphic omitted]OH)CH₃}X(L)](X = Cl or Br; L = CO, PMe₂Ph, PPh₃, or pyridine). The salts [Pd(CH₂C(CH₃)₂C(NOH)CH₃}(Ph₂PCH₂CH₂PPh₂)](X = l or BPh₄) have also been prepared. E-Ethyl t-butyl and E-phenyl t-butyl ketoximes are similarly cyclopalladated, but oximes of other carbonyl compounds, e.g. trimethylacetaldehyde, methyl isopropyl ketone, di-isopropyl ketone, ethyl methyl ketone, or 2-methylcyclohexanone, give dark intractable products. In contrast, methyl t-butyl NN-dimethylhydrazone with Na₂[PdCl₄] and Na[O₂CMe] cyclometallates regiospecifically on the single methyl group to give [Pd₂{CH₂C(NNMe₂)Bu^t}₂Cl₂]. The corresponding bromide or iodide complexes have been made as have bridge-split derivatives (with PMe₂Ph, PPh₃, or pyridine) and also an acetylacetonate, [[graphic omitted]Me₂)Bu^t}(acac)](6), the crystal structure of which has been determined. NN-Dimethylhydrazones of acetaldehyde, acetone, cyclohexanone, or 4-t-butylcyclohexanone cause decomposition on attempted cyclopalladation. Acetophenone NN-dimethylhdrazone cyclopalladates specifically on the 2 position of the benzene ring (i.e. not on the C-methyl group). Methyl t-butylketazine cyclopalladates specifically on a t-butyl methyl giving [Pd₂{CH₂C(CH₃)₂C(NNCMeBu^t)CH₃}₂Cl₂]: dimetallation could not be effected. Acetoxime O-allyl ether in methanol is cyclopalladated with concomitant attack by OMe to give [[graphic omitted]C-(CH₃)₂}₂Cl₂]. The corresponding ethoxy-compound is formed in ethanol; cyclohexanone oxime O-allyl ether is similarly palladated. Crystal data are: (1a), Monoclinic, space group P2₁/c, a= 7.312(1), b= 8.539(2), c=28.478(4)Å, β= 91.74(1)°, and Z= 4; (6), Triclinic, space group P, a= 9.573(3), b= 10.714(3), c= 8.983(2)Å, α= 94.41(2), β= 113.76(2), γ= 104.65(2)°, and Z= 2.