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Three new di-metallorganic cobalt complexes of the type trans-(Bz)2Co(chel), where Bz is a benzyl group σ-bonded to cobalt atom and chel is an equatorial chelating system constituted by an amino-oximic ligand and its conjugated base, were synthesised. The protonated and the unprotonated ligands interact through an O–H ⋯ O bridge stabilising the entire structure. The complexes differ in the equatorial moiety which is derived from the following ligands: HLN-py=3-[(2-pyridyl)ethylimino]-butan-2-one oxime), HLN-Ph=3-[(2-phenyl)ethylimino]-butan-2-one oxime and the analogous HLN-PhCl=3-[(2-chlorophenyl)ethylimino]-butan-2-one oxime. Two of these compounds, namely those derived from HLN-py and HLN-PhCl were structurally characterised by means X-ray diffractometry. Data reveal that each complex is characterised by the presence of two unusually long cobalt–carbon bonds which are 2.120(4) A (mean value) in complex with HLN-py ligand and 2.119(4) A (mean value) in complex with HLN-PhCl. These data are consistent with a strong mutual trans-influence exerted by one ligand on the other.

Polymerization of phenylacetylene to give highly stereoregular cis-transoid polyphenylacetylene is accomplished by use of [Rh(nbd)(OMe)]2 (nbd=norbornadiene) and Ph2P(CH2)xPPh2 (x=2, dppe; x=3, dppp; x=4, dppb). The catalytic system employing the ligand dppb promotes formation of polymer products with low polydispersities. The polymerization is of living nature, as proved by the dependence of polymer molecular weight on conversion and on initial monomer concentration, with molecular weight distributions always maintained within a narrow range. NMR studies of the catalytic system provide information on the rhodium chemistry involved, as well as useful means of comparison to other rhodium–phosphine catalytic systems.

Some new copper(II) complexes with TPEEN (TPEEN = N, N, N′, N′ -tetrakis(2-pyrid-2-yl-ethyl)1, 2-ethylenediamine) have been prepared. The X-ray diffraction structure of the |CuTPEEN| (PF 6 ) 2 · 1.5 acetone complex is reported. The [CuTPEEN] 2+ cation has a slightly distorted square pyramid coordination, in which the two tertiary nitrogens and three nitrogens of the pyridine arms are involved.

Axial alkyl or aryl groups, o -bonded to the metal atom in some tetradentate Co III complexes, are readily removed by iodine or iodine monochloride; electrophilic and radical attack on the carbon atom both can occur, depending upon the nature of the axial organic group and the chelating agent.