Turiddu Tarantelli

Some new complexes of nickel(II) halides with N,N′-disubstituted thioureas

Abstract Some new complexes of nickel(II) halides with sym-diphenyl-, sym-di-n-butyl, symdiallyl-, sym-allylethyl-thioureas have been prepared having general formulas NiL2X2, NiL4X2 and NiL6J2. The compounds of 1:6 type is the first hitherto prepared with substituted thioureas and magnetic studies show that solid compound NiL2X2 have tetrahedral, NiL4X2 tetragonal and NiL6J2 octahedral structures. In all case the thioureas are probably bonded to nickel through their sulfur atom. Magnetic moments of solid 1:4 compound vary with temperature according to a tetragonal structure with a singlet ground state and a thermally populated triplet excited state. In acetone solution all these compounds lose ligands to give tetrahedral species NiL2X2 according to NiLnX2 → NiL2X2 + (n−2) L.

Ultraviolet photoelectron spectroscopic investigation of electronic structure of some organic thio- and isothio-cyanates and their selenium analogues

He(I) photoelectron spectra of CH3SCN and CH3SeCN exhibit a series of five ionization bands < 15 eV, the first four being assigned to a sequence of n, π and σ orbitals of the S(Se)CN group on the grounds both of empirical correlations with simpler molecules, and of semi-empirical and ab initio quantum mechanical calculations. Theoretical calculations are reported and discussed also for the isomeric CH3NCS molecule, already reported in the literature, but re-examined here for comparison. In phenyl-substituted thio- and isothio-cyanates and their selenium analogues, photoelectron spectra are dominated by the presence of strong benzenoid bands, yet some general trends related to structural effects can be recognized.

Cobalt(II) complexes of ligands having several thiourea, or selenourea, groups

Abstract The ligand behaviour of polymethylenebis(phenylthiourea), L, compounds: PhNH·C-S·NH·CH 2 ·CH(Me)·NH·CS·NHPh (I); PhNH·CS·NH·(CH 2 ) n ·NH·CS·NHPh ( n = 2–10) (II)-(X) and triethylaminetris ((phenylthiourea), N(C 2 H 4 NH·CS·NHPh) 3 (XI), towards CoX 2 (XCl, Br and I)_and Co(ClO 4 ) 2 ·6H 2 O has been investigated. The halides all give tetrahedral complexes CoLX 2 , having chromophore CoS 2 X 2 . Complexes with L = (XI) probably contain a non-coordinating sulphur atom and have low magnetic moments (3·7-3·9 B.M.). Complexes of formula CoL 2 (ClO 4 ) 2 are formed with cobalt II perchlorate, although only those with L = (III)–(IV) could be separated as solids. These complexes are tetrahedral with a CoS 4 chromophore. Ligand (IV) also gives a complex of composition CoL 4 (ClO 4 ) 2 , which is probably pentacoordinate with a CoS 4 O chromophore, and is characterised by a rather high magnetic moment (5·25 B.M.). (IV) appears to coordinated as a monodentate ligand in this complex. The complex with L = (XI) is difficult to classify as tetrahedral. A comparison of these complexes with several analogues containing selenium in place of sulphur has been carried out.

Coordination by “soft” donors: Ni(II) complexes of N,N′-substituted selenoureas

N,N′-alkyl- and aryl-substituted selenoureas, R1NHCSeNHR2 (L) form Se-bonding tetrahedral complexes of formula NiL2X2 with Ni(II) halides, and square-planar complexes of formula NiL4(ClO4)2 with nickel(II) perchlorate. In contrast with the thioureas, tetragonal, NiL4X4, and octahedral, NiL6X2 and NiL6(ClO4)2, could not be prepared. With one particular selenourea a complex of formula NiL3Br2 was obtained, which exists only in the solid state. An analogous thiourea complex does not exist.

Complexes of Ni(II) perchlorate with substituted thioureas

Abstract Complexes of nickel(II) perchlorate with N - or N,N ′-substituted thioureas ( L ) exist in the solid state as octahedral Ni L 6 (ClO 4 ) 2 or, more rarely, as quadratic low-spin Ni L 4 (ClO 4 ) 2 . In acetone solutions, octahedral [Ni L 6 ] 2+ is easily dissociated to quadratic [Ni L 4 ] 2+ , and the latter in turn can be solvoyzed to pseudooctahedral species of the [Ni L 4− χ (acetone) 2+ χ ] 2+ type. Low temperature strongly favores dissociation of thiourea ligands.

Transition metal complexes of sulfur-oxygen chelating ligands Synthesis and characterisation of polymethylen-1-(phenylthiourea)-n-(phenylurea) complexes of cobalt(II)

Abstract Cobalt(II) halides, CoX2 (X = Cl, Br, I), give complexes of composition CoLX2 and CoL2X2 with polymethylene-1-(phenylthiourea)-n-(phenylurea) (L = Ph·NH·CS·NH·(CH2)n·NH·CO·NH·Ph) ligands. In the former the ligand bonds via S + O or S + N atoms, i.e. acts as a chelating ligand; in the latter the ligand is, instead, monodentate and bonds via the S atom. All the complexes are non-electrolytes and all have structures of approximately Td symmetry, with bonding halide ions.

Transition metal complexes of organo-selenium chelating ligands—nickel(II) complexes of polymethylenebis(phenylselenourea) compounds

Abstract Some polymethylenebis(phenylselenourea) (=L) complexes of nickel(II) halides have been prepared and characterised and compared with those of the sulphur analogues. The complexes, of formula NiL 2 X 2 , show magnetic moments which range between 0 and 3.0 B.M. depending on the temperature of preparation. At low temperature of preparation they tend to diamagnetism. The electronic spectra are not influenced by the halogen present. An interpretation of this behaviour is put forward based on the tetragonality of the NiSe 2 chromophore present and it is suggested that the singlet and triplet states are of virtually equal energy. The reaction of the ligands with nickel(II) perchlorate is described.