The exchange of pyridine on bis-pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. A nitrogen-14 magnetic resonance study

1983 ◽  
Vol 36 (10) ◽  
pp. 2019 ◽  
Author(s):  
J Sachinidis ◽  
MW Grant
Keyword(s):  
Magnetic Resonance ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Adduct Formation ◽  
Lewis Acidity ◽  
Magnetic Resonance Study ◽  
Square Planar ◽  
Square Planar Complexes ◽  
The Relationship

14N n.m.r. has been used to measure the rates of pyridine exchange of a series of bis pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. Substantial variations in the lability of the coordinated pyridine are observed, k,, at 298 K varying from about 103 to 107 s-1. In the monothioacetylacetonate series the lability of pyridine decreases as the electron withdrawing power of the substituents increases. Both the lability and the sensitivity to substituent effects are greater than for the analogous acetylacetonate derivatives. The relationship between the intrinsic Lewis acidity of the nickel(II) centre in the parent square-planar complexes as measured by equilibrium constants for bis pyridine adduct formation and the lability of pyridine in the adducts is explored.

A Nuclear Magnetic Resonance Study of the Conformation of Six-membered Chelate Rings in Four-coordinate Complexes

1975 ◽  
Vol 53 (3) ◽  
pp. 366-372 ◽  
Author(s):  
William R. Cullen ◽  
Laurance D. Hall ◽  
John T. Price ◽  
Gregory Spendjian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Central Atom ◽  
Nuclear Magnetic Resonance Study ◽  
Dihedral Angles ◽  
Group Viii ◽  
Magnetic Resonance Study ◽  
Square Planar ◽  
Square Planar Complexes ◽  
Chelate Rings

The ditertiary arsine (CH3)2AsCH2CH(C(CH3)3)CD2As(CH3)2 (L–L) forms 'tetrahedral' (L–L)Ni(CO)2 and square planar (L–L)NiOC(CF3)2C(CF3)2O. In both complexes the conformations of the chelate rings are locked with the t-butyl groups equatorial. The dihedral angles are very similar in spite of the anticipated differences in angles at the central atom. The square planar complexes (L–L)′PtbipyCl2 and (L–L)2′PtCl2 and their palladium analogs ((L–L)′ = H2NCH2CH(C(CH3)3)CD2NH2) also have their chelate rings in locked chair conformations. This results in the identification of isomers in the case of (L–L)2′M2+. The 3JH–H couplings indicate that the dihedral angles are similar in the group VIII complexes with a degree of puckering which could be less than in related complexes of L–L. The 3JPt–H couplings indicate changes in the puckering about the N … N axis.

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