Ronald S. Nyholm

The structure of bis-pyridine metal dihalide complexes

Abstract The structures of complexes of the type M II (Hal) 2 . 2 Pyridine have been investigated by a variety of physical techniques. Particular attention has been paid to the cobalt complexes which can exist in one or both of two isomeric forms. The factors which decide whether the tetrahedral monomer or octahedral polymer form will be the more stable are discussed. By using various metals five different types of complexes of the above formula have been identified — (a) tetrahedral monomer; (b) octahedral polymer; (c) square planar monomer; (d) tetragonal polymer; (e) (presumably) irregular tetrahedral monomer. The influence of the electronic configuration of the metal and the effect of the ligand on the structure adopted are discussed.

Infrared spectra of some nitrato and other oxy-anion co-ordination complexes

Abstract The infrared absorption spectra of a number of nitrato complexes of metals have been examined in the region between 4000 and 700 cm −1 . Assignments have been made for vibrations, characteristic of the co-ordinated nitrato group. Strong absorption bands, which do not occur in ionic nitrates, appear in the regions 1480–1530 and 1250–1290 cm −1 . The absorption arising from the vibration, ν 1 , theoretically inactive for the NO 3 − ion, occurs as a strong peak in the nitrato complexes within the range 1034-970 cm −1 . Using the frequency ν 2 , observed for these complexes, as a criterion of the degree of covalent character of the metal-nitrate bond, the following series is obtained: Ce IV Ni II Co III P II Pt IV . Carbonato and sulphato complexes are being studied. Similar results have been obtained for the carbonato complexes.

Oxygen-17 nuclear magnetic resonance of inorganic compounds

The 17O chemical shifts of a number of com pounds have been measured at 6.000 Mc/s in the liquid or solution state. The resonances observed for the ‘closed-shell’ oxy-anions of the transition metals indicate a high degree of paramagnetic shielding of the oxygen nuclei for these anions. A linear relationship has been observed between the chemical shifts for these anions and their lowest-energy electronic transitions as obtained from u.v. and visible spectra. Calculations in term s of a molecular orbital model for these anions have successfully accounted for this relationship and at the same time have produced a mechanism for the observed paramagnetic shielding. It has been shown that a similar linear relationship exists in the cases of organic carbonyl compounds for which nuclear resonance and optical spectral data are available.

Oxidative addition reactions in cluster complexes of osmium: Intracluster reactions of benzyne and a novel 'phenyl' complex

Abstract The structures of HOs3(CO)7(PPh2)(PPh3)(C6H4), HOs3(CO)8(PPh3)(PPh2C6H4) and HOs3(CO)7(PPh2)(PPh2C6H4C6H3) are described, the latter illustrating an intracluster reaction of the coordinated benzyne ligand.

Magnetochemistry: Introductory lecture

Abstract The simple fundamentals of magnetic susceptibility and its determination are first summarised and the various types of magnetic behaviour indicated. The theoretical basis of magnetic susceptibility is outlined and paramagnetism is discussed in some more detail. The latter is divided into various types depending upon the multiplet separation and the strength of the electrical ligand field around the ion. The applications of magnetic susceptibility measurements to valency problems are then discussed, attention being drawn to the uncertainty existing when metal-metal interaction occurs. The relationship of susceptibility and bond type is discussed and the limitations are emphasised. The way in which paramagnetic measurements may be used to determine the stereochemistry of transition metal complexes is surveyed. In addition to a survey of the use of the number of unpaired d electrons for this purpose the way in which the deviation from the spin-only moment may be employed is also discussed. The importance of the Kotani theory in providing an understanding of strong field complexes in which the moment is less even than that expected from the Pauling theory is emphasiesed. Tables of the magnetic behaviour of spin free and spin paired complexes are provided.

Metal complexes of unsaturated phenols and benzenethiols

Abstract The preparation and properties of complexes of o-vinylbenzenethiol, o-allylbenzenethiol with palladium and platinum and of o-allylphenol with palladium, platinum and rhodium are reported. Their behaviour towards oxidation with bromine is also described.

A 1H NMR investigation of the isomerism of a dimeric tertiary arsine chelate compound containing platinum(II)-carbon σ-bonds.

Abstract The Pt II complex of the chelate ligand ortho -vinylphenyldiphenylarsine (VPA) is susceptible to nucleophilic attack at the coordinated olefin to give four geometrical isomers of a dimeric product containing PtC σ-bonds. The NMR spectra of the monomers obtained by cleavage of the chlorine-bridged dimer with acetylacetonate or hexafluoroacetylacetonate show that methoxide attack occurs exclusively at the β-carbon atom to give a five membered chelate ring in which the α-carbon and arsenic atoms are the donors.

Preparation and properties of some mercury halide–platinum compounds and crystal structure of di-µ-chloro-(dichloromercurio)bis(dimethylphenylphosphine)platinum(II)

The compounds (I)—(VI)(PPhMe2)2PtX2(HgY2)(X = Cl, Br, or I; Y = Cl or Br) have been prepared by the action of mercury(II) halide on cis-(PPhMe2)2PtX2. The crystal structure of (I; X = Y = Cl) has been determined from diffractometer data. Crystals are monoclinic, space group P21/c, with Z= 4 in a unit cell of dimensions : a= 909·2(3), b= 1043·8(4), c= 2428·6(8) pm, β= 105·12(2)°. The structure was solved by Patterson and Fourier methods and refined by least-squares to R 0·057 for 2184 independent reflections. The complex contains two bridging chlorine atoms between Pt and Hg, the co-ordination being essentially square planar about Pt and distorted tetrahedral about Hg. Bond lengths suggest that HgCl2 is only weakly co-ordinated.

Some mercury halide-cobalt(II) and -nickel(II) compounds

Abstract The complexes (PEt 3 ) 2 Hg Y 2 MX 2 ( M  Co , X  Y  Cl or Br; M  Ni, X  Y  Cl) have been prepared by the action of mercuric halides on (PEt 3 ) 2 MX 2 . Magnetic properties, electronic spectra and conductivity measurements have been used to confirm their structure, which contains two bridging chlorines between the mercury and the transition metal.