(β-Diketiminato)palladium Complexes

Reaction of Pd(acac)2 with 1 equiv of the lithium β-diketiminate Li(iPr2-nacnac) (iPr2-nacnac =
CH{C(Me)NiPr}2) affords the dark red mixed-ligand complex (acac)Pd(iPr2-nacnac) (1), while with 2
equiv of Li(iPr2-nacnac) the light red homoleptic Pd(iPr2-nacnac)2 (2) is formed. A similar reaction of
Pd(acac)2 with the more bulky (THF)Li(Ar2-nacnac) (Ar2-nacnac = CH{C(Me)N(C6H3-2,6-iPr2)}2)
proceeds only to the stage of the mixed-ligand complex. While below 0 °C red (acac)Pd(κ2N,N-Ar2-nacnac) (4) is isolated as the kinetically controlled product, which is stable in the solid state, this complex
isomerizes in solution at ambient temperature to yield the lighter red and chiral (acac)Pd(κ2C,N-Ar2-nacnac) (5), displaying a novel nacnac bonding mode. The reaction of [Pd(MeCN)4](BF4)2 and that of
the Pd(I) complex [Pd2(MeCN)6](BF4)2 with (THF)Li(Ar2-nacnac) gives [(κ2N,N-Ar2-nacnac)Pd(MeCN)2](BF4) (6). The κ2N,N-Ar2-nacnac ligand in 6 is sufficiently nucleophilic to displace acetonitrile from
[Pd(MeCN)4](BF4)2 and produce the pure dinuclear [(MeCN)3Pd{μ-CH(C(Me)NAr)2}Pd(MeCN)2](BF4)3
(A), previously accessible only in a mixture. From the reactions of {(η3-C3H5)Pd(μ-Cl)}2 with Li(iPr2-nacnac) and (THF)Li(Ar2-nacnac) the mixed-ligand complexes (η3-C3H5)Pd(iPr2-nacnac) (3a) and (η3-C3H5)Pd(κ2N,N-Ar2-nacnac) (3b) have been obtained. Reaction of (cod)PdMeCl with (THF)Li(Ar2-nacnac)
affords (Ar2-nacnac)PdMe(MeCN) (7). An anisotropic effect of the Ar2-nacnac ligand in the 1H NMR
spectra of 3b and 4 can be noted. The structures of 2, 3a, 4, and 5 have been determined by X-ray
crystallography.