Synthesis and study of Pt(II)–nitrile complexes. Multinuclear NMR spectra and crystal structures of compounds of the types [Pt(R-CN)Cl₃]⁻ and cis and trans-Pt(R-CN)₂Cl₂

Complexes of the type [Pt(R-CN)Cl-3](-) were synthesized and studied by H-1, C-13 and Pt-195 NMR spectroscopies. The (2)J(Pt-195-C-13) coupling constants are about 240 Hz. The signals due to the cyano carbon atoms of the coordinated ligands were observed at higher fields than those of the free ligands. The shielding on the cyano carbon increases as the alkyl chain lengthens and also when the branching increases. The Pt-195 signals of all the complexes were observed around -2000 ppm. The crystal structures of (NMe(4))[Pt(C3H7-CN)Cl-3] (1) and (NMe(4))[Pt(p-HO-C6H4-CN)Cl-3] (2) were determined. Compound 1 is monoclinic, P2(1)/c, a = 8.384(5), b = 15.336(19), c = 11.759(9) Angstrom, beta = 99.52(6)degrees, Z = 4, R = 0.054, and wR = 0.051. Crystal 2 is tetragonal with a = 16.222(6), c = 12.052(5) Angstrom, Z = 8, R = 0.059, and wR = 0.044. The Pt-Cl bond trans to the nitrile ligand is shorter than normal (2.276(3) Angstrom for 1 and 2.264(7) Angstrom for 2) while the two other bends are normal (2.293(4), 2.287(3) Angstrom for 1 and 2320(7), 2.275(8) Angstrom for 2). The Pt-N bonds are 1.97(1) Angstrom (1) and 1.92(2) Angstrom (2) and the segments Pt-N=C-C are linear. Disubstituted compounds were also synthesized and studied by multinuclear NMR. The Pt-195 signals of the cis isomers were observed at lower fields than those of the trans isomers (Delta approximate to 65 ppm), while the C-13 signals of the cyano carbons of the trans isomers were observed at lower fields than those of the cia compounds (Delta approximate to 0.6 ppm). The cis complexes isomerize to the trans compounds upon heating. The crystal structures of cis-(3) and trans-Pt(C2H5-CN)(2)Cl-2 (4) and also of cis-Pt(p-HO-C6H4- CN)(2)Cl-2 (5) were determined. Crystal 3 is monoclinic, P2(1)/c, a = 7.506(5), b = 9.539(5), c = 14.823(7) Angstrom, beta = 92.31(4)degrees, Z = 4, R = 0.050, and wR = 0.042. The trans isomer 4 is monoclinic with the Pt atom on an inversion centre, P2(1)/c, a = 5.149(4), b = 9.394(8), c = 10.944(10) Angstrom, beta = 97.84(7)degrees, Z = 4, R = 0.017 and wR = 0.020. Finally, compound 5 is triclinic, P-1, a = 7.464(3), b = 10.712(6), c = 12.291(5) Angstrom, alpha = 75.63(4)degrees, beta = 75.63(4)degrees, gamma = 80.32(4)degrees, Z = 2, R = 0.045, and wR = 0.056. The Pt-Cl bond distances for the cis isomers are 2.269(5), 2.270(4) Angstrom for 3 and 2.274(2), 2.279(3) Angstrom for 5 while they are 2.289(3) Angstrom for the transisomer (4). The Pt-N bonds are 1.962(14), 1.988(11) Angstrom (3), 1.972(7), 1.976(7)Angstrom (5) and 1.969(5) Angstrom for 4.