LINKAGE ISOMERIZATION EQUILIBRIA IN (CHLORANILATO)PALLADIUM(II) COMPLEXES WITH AMINE LIGANDS - CRYSTAL-STRUCTURE OF (CHLORANILATO)BIS(ACETONITRILE)PALLADIUM(II)

A series of (chloranilato)palladium(TI) complexes of the type [Pd(CA)( amine)(2)] have been prepared to probe inductive effects on linkage is omerization between dicarbanion (C-CA) and quinonoid (pi-CA) form of t he bidentate chloranilate ligand. Electronic, infrared, and H-1 NMR sp ectra of [Pd(CA)(py-4-X)(2)] species (X = H, C(CH3)(3), COOH, C(O)NH2, N(CH3)(2), OH, CN, NH2) show an unexpected mixture of C-CA and pi-CA isomers whose distribution is insensitive to variations in the X subst ituent. Evidence is presented that Pd(CA) complexes with py-4-X ligand s have variable structures which depend strongly on the solvent employ ed in their synthesis. The first high-resolution crystal structure of a C-bonded CA(2-) complex is reported. [Pd(C-CA)(CH3CN)(2)] crystalliz es in the triclinic P (1) over bar space group with a 8.681(2) Angstro m, b = 11.371(2) Angstrom, c = 13.997(3) Angstrom, alpha = 91.32(1)deg rees, beta = 97.28(1)degrees, gamma = 96.129(5)degrees, and V = 1361.5 (7) Angstrom(3); Z = 4. Chloranilate ligates Pd(II) through both C-Cl carbon atoms, with identical Pd-C and Pd-N bond lengths of 2.09 and 2. 07 Angstrom, respectively. Bond angles of the two carbon-donor atoms s pan the interval from 90.8 to 121.7 degrees, with Pd-C-C and all other angles around the coordinated C atoms falling in the ranges 90.8-95.6 and 112.5-121.7 degrees, respectively. The chloranilate ligand adopts a boat conformation (132.7 degrees bend angle), and Pd(II) has a dist orted square-planar coordination geometry characterized by average C-P d-C, C-Pd-N, and N-Pd-N angles of 77.5, 95.1, and 92.4 degrees, respec tively.