Martin L. Tobe

Platinum(II) complexes containing dimethylsulphoxide and linear aliphatic diamines formation of a seven-membered chelate ring

Abstract The synthesis and properties of complexes of the type [Pt(diamine)(dmso)Cl]Cl containing chelate rings of increasing size are reported (dmso = dimethylsulphoxide; diamine = 1,2-diamminoethane (en), 1,3-diaminopropane (tn), and 1,4-diaminobutane (bn)). The 1,4-diaminobutane complex contains the rate seven-membered ring and is formed together with a binuclear complex, trans-[Pt(dmso)Cl2]2(NH2(CH2)4NH2), in which the amine bridges two platinum atoms. The compounds have been characterised by analysis, conductance, spectroscopic and nuclear magnetic resonance measurements. On heating the en and the tn complexes under reduced pressure dimethylsulphoxide is lost and the corresponding uncharged [Pt(diamine)Cl2] species is formed.

Kinetics of the displacement of cyclobutane-1,1-dicarboxylate from diammine(cyclobutane-1,1-dicarboxylato)platinum(II) in aqueous solution

The displacement of 1,1-cyclobutanedicarboxylate (cbdca2–) from [Pt(NH3)2(cbdca)] has been studied in aqueous solution. In the presence of acid the process resembles the successive displacement of two monodentate carboxylates. The first (ring-opening) stage follows the rate law kobs.=(k0+k1k0[H+])(1 +k0[H+])–1, k0= 8 × 10–5 s–1, K0= 0.6 dm3 mol–1, k1= 8.0 × 10–4 s–1 at 25 °C, while the second follows the simple relationship kobs.=k[H+], k= 1.61 × 10–4 dm3 mol–1 s–1 at 25 °C. In the absence of acid and other nucleophiles the complex is inert and in the presence of chloride the displacement of ligand follows a first-order dependence on [Cl–], kobs.=kCl[Cl–]. At 80 °C, kCl= 1.32 × 10–4 dm3 mol–1 s–1. The chelate differs from the bis-monodentate carboxylate species in the great importance of the reverse, ring-closing process, which can be prevented in the presence of acid.

The crystal and molecular structure of an isomer of chloro [1,9-bis(2-pyridyl)-2,5,8-triazanonane] cobalt(III), tetrachlorozincate(II), [Co(picdien)Cl]ZnCl4

Abstract The structure of the title compound has been determined by counter data. The crystals are orthorhombic, space group P bca , with a = 16.363(7), b = 18.382(8), c = 14.940(6) A, Z = 8. The structure has been defined by full-matrix least-squares to a final conventional R value of 0.092 ( R w = 0.081 ). The coordination geometry of the complex cation is near regular octahedral, with the pentadentate picdien ligand present in the α,β configuration and with a Cl trans to an ‘angular’ secondary nitrogen. Only two, i.e. , one ‘angular’ and the ‘flat’ of the three secondary nitrogen atoms of the picdien ligand exhibit chirality and it is opposite. The absolute configuration of the complex can be designed as Δ-α, β-R (or Λ-α, β-S). The ZnCl 4 anion assumes a distorted tetrahedral configuration.

Preparation and spectroscopic properties of some low spin trigonal bipyramidal d8 metal complexes

Abstract The preparation of (o−Me 2 As.C 6 H 4 ) 3 As, (Qas), and of complexes [MX Qas]Y (M = Ni; X = Cl, Br, I, NCS, NO 2 , N 3 , NO 3 , CH 3 COO; Y = X − , BF 4 − BPh 4 − : M = Pd or Pt; X = Cl, Br, I, NCS; Y = X − BF 4 − , BPh 4 − are described. All the complexes are diamagnetic, five-coordinate species and behave as 1:1 electrolytes in polar solvents. The visible and near UV spectra contain bands attributable to d–d transitions the intensities of which, although relatively high, are appreciably lower than those of the analogous complexes of (o−Ph 2 As.C 6 H 4 ) 3 As, (QAS). It is concluded that the ligand bands in [MX QAS]Y «borrow» intensity from π * ←π transitions of the phenyl groups. Towards the metals used in this investigation Qas is a better ligand than the previously investigated QAS.

Crystal and molecular structure of chloro[1,11-bis(2-pyridyl)2,6,10-triazaundecane]cobalt(III) tetrachlorocobaltate(II) hemihydrate, [Co(picditn)Cl] CoCl4·H2O

The structure of the title compound has been determined by counter data. The crystals are orthorhombic, space group P212121 with a = 16.069(8), b = 13.215(6), c = 11.490(5) A, Z = 4. The structure has been refined by full-matrix least-squares to a final conventional R value of 0.049. The coordination geometry of the complex cation is near regular octahedral, with the pentadentate ligand present in the α,β configuration and with a Cl trans to an ‘angular’ secondary nitrogen. The absolute configuration of the complex ion can be designed as Λ while the two optically active N(2) and N(4) are R a;nd S respectively.

Mode of binding of dimethyl sulphoxide in platinum(II) and palladium(II) cationic complexes containing a chelated diamine. X-Ray crystal structures of (2,2′-bipyridyl)chloro(dimethyl sulphoxide-O)palladium(II) tetrafluoroborate and chloro(dimethyl sulphoxide-S)(ethylenediamine)palladium(II) perchlorate

The mode of binding of dimethyl sulphoxide (dmso) in cations of the type [M(N–N)(dmso)Cl]+[M = Pd or Pt; N–N = 2,2′-bipyridyl (bipy), 1, 10-phenanthroline (phen), or ethylenediamine (en)] has been examined by i.r. and 1H n.m.r. spectroscopy. Infrared spectra of the complexes in the solid state indicate that dmso binds through oxygen in the palladium(II) adducts containing bipy and phen, and through sulphur in the other cases. Proton n.m.r. spectra in CD3NO2 solution show that the complexes in which dmso is S-bonded in the solid state retain their structure in solution, while those containing O-bonded dmso equilibrate to a mixture of O- and S-bonded isomers whose composition depends upon the nature of the chelated diamine. Interconversion between the two isomers is slow on the n.m.r. time-scale, while exchange of S- and O-bonded dmso is fast. The crystal and molecular structures of [Pd(bipy)(dmso)Cl][BF4], (1), and [Pd(en)(dmso)Cl][ClO4], (2), have been determined by X-ray diffraction: (1) crystallizes in the triclinic space group P with Z= 2, a= 10.318(1), b= 12.503(1), c= 7.436(1)A, and α= 95.40(1), β= 109.10(1), γ= 109.75(1)°; (2) crystallizes in the monoclinic space group P21/n with Z= 4, a= 9.960(1), b= 8.652(1), c= 14.152(2)A, and β= 92.25(1)°. The structures were solved by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.026 and 0.024 for (1) and (2), respectively. The co-ordination geometry of the metal atom is square planar in both cases; in complex (1) the dmso ligand is oxygen bonded, while in (2) it is sulphur bonded. The geometries of O- and S-bonded dmso differ considerably: in (2) the SO distance, O–S–C and C–S–C angles correspond to the geometry of free dmso; in (1) the SO distance is intermediate between single and double bond lengths, the two O–S–C angles increase by some 7° with respect to S-bonded dmso, while the C–S–C angle increases only by 3.6°.

Base-catalysed aquation of αβ-syn- and αβ-anti-chloro- and bromo-[1,9-bis(2′-pyridyl)-2,5,8-triazanonane]- and -[1,11-bis(2′-pyridyl)-2,6,10-triazaundecane]-cobalt(III) cations. An unusually base-sensitive halogenopentamine cobalt(III) system

Complexes of the type [Co(picdien)X][ClO4]2 and [Co(picditn)X][ClO4]2[picdien = 1,9-bis(2′-pyridyl)-2,5,8-triazanonane, picditn = 1,11-bis(2′-pyridyl)-2,6,10-triazaundecane; X = Cl, Br, NO2, NCS, N3, MeCO2, or H2O] have been prepared. All complexes have the αβ configuration, those of picdien existing in either or both syn and anti forms, while only the anti forms of the picditn complexes have been isolated. Structures have been established by single-crystal X-ray diffraction and 1H n.m.r. spectroscopy in dimethyl sulphoxide and D2O. All complexes are unusually sensitive to base-catalysed hydrolysis over very wide ranges of pH. The pH-independent contribution to the solvolysis of the chloro- and bromo-picdien complexes is observed only at high temperatures and at high [H+] but there is a very important pH-independent contribution to the solvolysis of the corresponding picditn species, which are also somewhat more sensitive to base catalysis. Proton-exchange studies show that proton transfer is faster than substitution in even the most labile systems. The mechanism is discussed.

The crystal and molecular structure of an isomer of chloro(1,5,8,11,14-pentaazacyclohexadecane) cobalt(III), diperchlorate, [Co(16-[ane]-5)Cl] (ClO4)2

Abstract The structure of the title compound has been determined by counter data. The crystals are orthorhombic, space group P n 2 1 a with a = 14.317(7), b = 13.484(7) and c = 10.361(6) A, Z = 4. The structure has been refined by full-matrix least-squares to a final conventional R value of 0.085 (Rw = 0.083). The geometry of the complex action is a relatively undistorted octahedron with a chlorine atom trans to an ‘angular’ secondary nitrogen of the pentadentate 16-[ane]-5 ligand. Within the ligand the six-membered ring assumes a ‘chair’ conformation, while all five-membered rings are ‘gauche’. Only one, i.e., the ‘angular’ N(1) trans to Cl(1) of the five secondary nitrogen atoms of 16-[ane]-5 does not exhibit chirality. The two ‘flat’ nitrogens have opposite chirality as do the two remaining ‘angular’ nitrogens. The ClO 4 anions assume a distorted tetrahedral configuration.

Dissociative substitution in four-co-ordinate planner platinium(II) complexes. The kinetic of sulphoxide exchange and its displacement by bidentate ligands in the reactions of cis- di(aryl)bis(dimethyl sulphoxide) platinum(II) in chloroform and benzene

A parallel flow 1H n.m.r. and u.v. spectrophotometric study of the exchange of Me2SO with (CD3)2SO, and the displacement of Me2SO by L–L [L–L = 2,2′-bipyridine, 1,10-phenanthroline, and 1,2-bis(diphenylphosphino)ethane] from cis-[Pt(Ph)2(Me2SO)2] in CDCl3 and benzene indicates that the main reaction path is dissociative with [Pt(Ph)2(Me2SO)] as the reactive intermediate.

The crystal and molecular structure of an isomer of Bromo [1,9-bis(2-pyridyl) 2,5,8-triazononane] cobalt(III), perchlorate, [Co(picdien)Br](ClO42and that of an isomer of nitro[1,9-bis(2-pyridyl)2,5,8-triazanonane]cobalt(III), perchlorate, [Copicdien)(No2)](ClO4)2

Abstract The structure of an isomer of bromo [1,9-bis(2-pyridyl)2,5,8-triazanonane] cobalt(III), perchlorate, [Co(picdien)Br](ClO 4 ) 2 , (I) and that of an isomer of nitro [1,9-bis(2-pyridyl)2,5,8-triazanonane]cobalt(III), perchlorate, [Co(picdien)(NO 2 )](ClO 4 ) 2 , (II), was determined by counter data. Crystal data are as follows: (I), a = 21.242(9), b = 21.732(9), 10.015(5) A , orthorhombic, P b c a, Z = 8; (II), a = 10.062(5), b = 28.553(9), c = 7.894(4) A , β = 97.9(1)°, monoclinic, I c, Z = 4. Full matrix least-squares refinement converged at R = 0.064, (I), and R = 0.068, (II). The coordination geometry of both complex cations is near regular octahedral, with the pentadentate picdein ligand present in the α, β configuration. The absolute configuration of (I) can be designed as Δ-α, β-R (or Λ-α, β-S) whereas that of (II) is Δ-α, β-S (or Λ-α, β-R). The ClO 4 anions assume a distorted tetrahedral configuration.