Synthesis and Characterization of Ambient Temperature Stable Organopalladium(IV) Complexes, Including Aryl-, h1-Allyl-, Ethylpalladium(IV) and Pallada(IV)cyclopentane Complexes. Structures of Poly(pyrazol-1-yl)borate Complexes PdMe3{(pz)3BH} and PdMe3{(pz)4B} and Three Polymorphs of PdMe2Et{(pz)3BH}

The palladium(II) complexes PdMe 2(tmeda), PdMePh(tmeda), and Pd(CH 2CH 2CH 2CH 2)-(tmeda) (tmeda = tetramethylethylenediamine) react with potassium tris(pyrazol-1-yl)borate and organohalides R″X in acetone to form the octahedral palladium(IV) complexes PdMeRR″-{(pz) 3BH} (R = Me, Ph) and Pd(CH 2CH 2CH 2CH 2)R″{(pz) 3BH} (R″X = MeI, EtI, PhCH 2Br, CH 2=CHCH 2I). The complexes are stable in the solid state and in solution at ambient temperature, PdMe 3{(pz) 3BH} is more stable than the iodide salt of isoelectronic [PdMe 3{(pz) 3-CH}] +, and the aryl- and η 1-propenylpalladium(IV) complexes are the first examples of aryl-and allylpalladium(IV) complexes that are stable above 0°C. The tris(pyrazol-1-yl)borate ligand considerably enhances the stability of palladium(IV) complexes when compared with related neutral donor ligands. The ethylpalladium(IV) complexes have stabilities in solution similar to that of the most stable ethylpalladium(II) complexes reported. The complex PdMe 3-{(pz) 4B} (2) has been prepared, and structural studies of this complex and PdMe 2R″{(pz)3-BH} [R″ = Me (1), Et (3)] completed, allowing the first comparison of structural parameters of ethylpalladium(II, IV) complexes and of PdMe 3{(pz) 3BH) with the "isoelectronic" cation [PdMe 3{(pz) 3CH}] +. Three polymorphs of PdMe 2Et{(pz) 3BH} were examined: complex 3a is ordered, but the other polymorphs exhibit disordering in the conformation of the ethyl group (3b) and in the position of the ethyl group and one of the methyl groups (3c). Crystallographic data: for 1, monoclinic, space group P2 1/c, a = 16.559(16) Å, b = 7.859(4) Å, c = 13.774(15) Å, β = 118.88(8)°, Z = 4, R = 0.032, R w = 0.043; for 2, monoclinic, space group P2 1/c, a = 11.453(1) Å, b = 9.729(2) Å, c = 16.973(9) Å, β = 107.25(3)°, Z = 4, R = 0.053, R w = 0.055; for 3a, monoclinic, P2 1/c, a = 9.384(3) Å, b = 12.795(3) Å, c = 15.119(8) Å, β = 115.22(3)°, Z = 4, R = 0.055, R w = 0.052; for 3b, orthorhombic, P2 12 12 1, a = 13.955-(3) Å, b = 13.152(18) Å, c = 9.047(6) Å, Z = 4, R = 0.052, R w = 0.053; for 3c, tetragonal, P4 32 12, a = 12.305(4) Å, c = 21.542(7) Å, Z = 8, R = R w = 0.035. © 1995 American Chemical Society.