Synthesis and Characterisation of [(en)2Co]3+ Complexes Coordinated by Substituted Thiourea Ligands

Substituted thiourea ligands bind in a bidentate manner forming a four-membered ring through the sulfur atom and a deprotonated thiourea nitrogen atom when reacted with [(en)2Co(OSO2CF3)2]+ in tetramethylene sulfone. Reaction of unsymmetrical ligands results in the formation of coordination isomers, some of which can be separated by column chromatography using Sephadex SPC-25. Coordination isomers are easily distinguishable based on visible and 1H NMR spectroscopy . Twelve para-substituted and one meta-substituted ligands were studied: N,N′-dibenzylthiourea (1a); N-(R)phenyl-N′-benzylthiourea {R = H (2a), NO2 (2b), CH3 (2c)}; N-(R)phenyl-N′-(R′)phenylthiourea {R, R′: H, H (3a), H, CH3 (3b), OCH3, NO2 (3c), CH3, NO2 (3d)}; N-methyl-N′-(R)phenylthiourea {R = H (4a), CH3 (4b), OCH3 (4c), NO2 (4d), 3-CH3 (4e)}. The solid state structure (X-ray) of one isomer of Co-4a as its perchlorate salt confirms the coordination mode suggested by 1H NMR spectroscopy and shows that the Co–N bond trans to the coordinated thiourea sulfur induces a structural trans effect of 0.019 Å.

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)Cl3]− were synthesized and studied by 1H, 13C, and 195Pt NMR spectroscopies. The 2J(195Pt-13C) 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 195Pt signals of all the complexes were observed around −2000 ppm. The crystal structures of (NMe4)[Pt(C3H7-CN)Cl3] (1) and (NMe4)[Pt(p-HO-C6H4-CN)Cl3] (2) were determined. Compound 1 is monoclinic, P21/c, a = 8.384(5), b = 15.336(19), c = 11.759(9) Å, β = 99.52(6)°, Z = 4, R = 0.054, and wR = 0.051. Crystal 2 is tetragonal with a = 16.222(6), c = 12.052(5) Å, 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) Å for 1 and 2.264(7) Å for 2) while the two other bonds are normal (2.293(4), 2.287(3) Å for 1 and 2.320(7), 2.275(8) Å for 2). The Pt—N bonds are 1.97(1) Å (1) and 1.92(2) Å (2) and the segments Pt-N≡C-C are linear. Disubstituted compounds were also synthesized and studied by multinuclear NMR. The 195Pt signals of the cis isomers were observed at lower fields than those of the trans isomers (Δ ≈ 65 ppm), while the 13C signals of the cyano carbons of the trans isomers were observed at lower fields than those of the cis compounds (Δ ≈ 0.6 ppm). The cis complexes isomerize to the trans compounds upon heating. The crystal structures of cis-(3) and trans-Pt(C2H5-CN)2Cl2 (4) and also of cis-Pt(p-HO-C6H4-CN)2Cl2 (5) were determined. Crystal 3 is monoclinic, P21/c, a = 7.506(5), b = 9.539(5), c = 14.823(7) Å, β = 92.31(4)°, Z = 4, R = 0.050, and wR = 0.042. The trans isomer 4 is monoclinic with the Pt atom on an inversion centre, P21/c, a = 5.149(4), b = 9.394(8), c = 10.944(10) Å, β = 97.84(7)°, 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) Å, α = 75.63(4)°, β = 75.63(4)°, γ = 80.32(4)°, 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) Å for 3 and 2.274(2), 2.279(3) Å for 5 while they are 2.289(3) Å for the trans isomer (4). The Pt—N bonds are 1.962(14), 1.988(11) Å (3), 1.972(7), 1.976(7) Å (5) and 1.969(5) Å for 4. Key words: platinum, nitrile, NMR, isomerization, crystal structure.

Seven coordination. 1. Synthesis, structure, and fluxionality of(CH3)2AsC(CF3)=C(CF3)As(CH3)2W(CO)2I2P(OCH3)3

(L—L)W(CO)4 (L—L = (CH3)2AsC(CF3)=C(CF3)As(CH3)2) is oxidized by I2 to yield the seven-coordinate complex (L—L)W(CO)3I2 which reacts with monodentate phosphines or phosphites to form (L—L)W(CO)2I2P (P = phosphine or phosphite). Crystals of (L—L)W(CO)2I2P(OCH3)3 are monoclinic, space group P21/c, a = 15.711(3), b = 13.134(2), c = 13.800(3) Å, β = 111.81(2)° with Z = 4. The structure was solved from a Patterson map and anisotropically refined by least squares to a conventional R value of 0.039 using 3737 independent reflections. The crystal structure showed the tungsten atom to be seven-coordinate with a geometry most closely approximated by a capped octahedral environment, the capping group being a carbonyl moiety ([W—C] = 1.95 (1) Å). The capped face consists of the carbon atom ([W—C] = 1.98(1) Å) of the remaining carbonyl, an arsenic atom ([W—As] = 2.556(1) Å), and the phosphorus atom ([W—P] = 2.466(3) Å). The W—As bond trans to a phosphite group is longer (by 0.050(2) Å) than the W—As bond trans to an iodine atom. 1H nmr data indicate the complex to be fluxional at 298 K and rigid at lower temperatures, the data at lower temperatures being consistent with the configuration found in the crystal. The nmr data at lower temperatures suggest two exchange processes are occurring; one which averages two sets of As—CH3 groups and another process which averages all four As—CH3 groups.

The synthesis and seven-coordinate structure of (CH3)2AsC(CF3=C(CF3)As(CH3)2W(CO)Br2[P(OCH3)3]2

(L–L)W(CO)4 (L–L = (CH3AsC(CF3)=C(CF3)As(CH3)2) is oxidized by Br2 to yield the seven-coordinate complex (L–L)W(CO)3Br2, which reacts with monodentate phosphines or phosphites to form (L–L)W(CO)Br2P2 (P = phosphine or phosphite). Crystals of (L–L)W(CO)Br2[P(OCH3)3]2 are monoclinic, space group P21/c, a = 19.110(5), b = 9.208(3), c = 17.845(6) Å, β = 108.93(2)° at 21 °C with Z = 4. The structure was solved from a Patterson map and refined by least squares to a conventional R value of 0.092 using 2330 independent reflections. The crystal structure indicated the tungsten atom to be seven-coordinate with the geometry most closely approximated by a capped trigonal prismatic environment, the capping group being a bromine atom (W—Br, 2.686(5) Å). The capped face consists of the remaining bromine atom (W—Br, 2.695(5) Å), a phosphorus atom (W—P, 2.465(9) Å), and the two arsenic atoms from the bidentate ligand (W—As, 2.619(3) and 2.526(4) Å). The W—As bond trans to a phosphite is significantly longer (by 0.093 Å) than the W—As bond trans to a bromine. The 1H nmr data indicate that the complex is stereochemically rigid at 25 °C and nonrigid at higher temperatures; however, the data at 25 °C are not consistent with the configuration found in the crystal.

Preparation and structure of mer-trichloro(acetonitrile)bis-(triphenylphosphine)osmium(III)

An air-stable, red, crystalline, N-bonded acetonitrile complex of Os(III), OsCl3(NCCH3)(P(C6H5)3)2, has been prepared and characterized by elemental analysis, magnetic susceptibility, and a single crystal X-ray structure determination. Crystals are monoclinic, space group P21/c, cell dimensions a = 10.029(2), b = 15.233(2), c = 25.246(4) Å, β = 113.65(1)°, and Z = 4. Three dimensional X-ray diffraction intensity data were collected on an automatic four circle diffractometer using Cu radiation. Full-matrix least-squares refinement on F converged at R = 0.038 for 4384 unique observations. The Os atom has a slightly distorted octahedral coordination geometry, with trans phosphine ligands, mean Os—P 2.406(2) Å. The acetonitrile ligand is σ-bonded through the N atom, Os—N 2.038(6) Å. The bond trans to the acetonitrile ligand. Os—Cl(1) 2.364(2) Å, is not significantly different from the mean of the cisOs—Cl bonds, 2.361(2) Å.

Synthesis and structure of a monothiooxalato cobalt(III) complex

The crystal and molecular structure of racemic bis(ethane-1,2- diamine)(thiooxalato-O,S)cobalt chloride hydrate ([Co(en)2(mtox)] Cl,H2O) has been determined by single-crystal X-ray diffraction techniques; all atoms, including hydrogens, have been refined by full-matrix least-squares procedures to a final R index of 0.032. The crystals are monoclinic, space group P21/c with a 7.548(1), b 14.249(2), c 12.317(2) Ǻ, β 109.27(1)°. The structure consists of discrete cations linked by hydrogen bonds to the chloride anion, water molecule and symmetry-related cation. The Co-N bond trans to Co-S is lengthened relative to the cis Co-N(en) lengths by 0.021(3) Ǻ. The complex is the only tractable product from the reaction of excess acetic anhydride in dimethyl sulfoxide with [Co(en)2(SCH2CO2)]+ ions. The mechanism of formation is discussed.