Structurally characterised cobalt(II) complexes containing pyridazine, triazole or triazolate ligands are the subject of this review. Firstly a brief introduction to Schiff-base macrocyclic chemistry ...is given and then the crystal structures and magnetic properties of pyridazine-containing cobalt(II) complexes are discussed, focussing on macrocyclic complexes. There follows a discussion of the crystal structures, as well as the magnetic behaviour where known, of cobalt(II) complexes containing the triazole moiety in a
N
1,
N
2-bridging fashion. Finally an overview of reported complexes where the triazole unit has been incorporated into a Schiff-base macrocyclic framework is provided. None of these triazole-containing macrocyclic complexes has been structurally characterised.
Square planar arenido(triphenylphosphane)nickel(II) complexes containing a heterocyclic bidentate N,O-chelate ligand are catalysts for the copolymerisation of ethene and carbon monoxide. To examine ...the influence of the N,O-ligand on the catalytic activity new nickel(II) complexes with altered heterocyclic ring size in the corresponding N,O-ligands were synthesised and fully characterised. The crystal structures of all protonated N,O-ligands and the corresponding nickel complexes were determined. The catalytic activity of the new complexes in the copolymerisation reaction of ethene and carbon monoxide as well as in the polymerisation reaction of ethene were studied.
The backbone of the N,O-chelate ligand of catalytically active arenidonickel(II) complexes containing triphenylphosphane was altered and the influence of different heterocyclic ring sizes on the catalytic activity of the nickel complexes was investigated both for the copolymerisation of ethene and carbon monoxide and the polymerisation of ethene. Display omitted
► Eight nickel(II) complexes were synthesised and used as catalysts for polymerisation. ► Three new N,O-chelate ligands were coordinated to different Ni precursor complexes. ► All ligand and three corresponding complex structures were determined. ► The catalytic activity for the copolymerisation of ethene and CO was investigated. ► Possible mechanistic explanations for the catalytic behaviour are discussed.
Nickel(II) complexes comprising electronically delocalised N,O‐chelating ligands are active catalysts in the copolymerisation of carbon monoxide and ethene. Elucidating the mechanism of catalysis ...presupposes the basic understanding of the intramolecular flexibility of such transition metal complexes. Several nickel(II) complexes with or without planar chirality were synthesised and characterised by NMR spectroscopic techniques and X‐ray diffraction.
Several arenidonickel(II) complexes of different β‐enaminonic N,O‐chelating ligands are presented. Rotation around the Ni–C bond is hindered, and thus planar chirality is introduced. Such complexes are active catalysts in the copolymerisation of ethene and CO.
Nickel(II) catalysed co-polymerisation of CO and ethene leads to alternating polyketone or polyketone/polyethene dependent on the co-catalyst used.
Display omitted
► Nickel(II)–arenido complexes are ...co-polymerisation catalysts. ► Co-polymerisation of ethene and CO. ► Boranes as co-catalysts trigger the formation of polyethylene. ► PPh
3 as co-catalyst completely suppresses the formation of polyethylene.
The square planar Ni complex (SP-4-3)-Ni(2-tol)(PPh
3)(N,O) (N,O
=
(Z)-4,4,5,5,6,6,6-heptafluoro-3-oxo-2-(pyrrolidine-2-ylidene)-hexanenitrile) is an active catalyst for the co-polymerisation of CO and ethene yielding aliphatic polyketone. Addition of Lewis acids like BPh
3 or B(C
6F
5)
3 as co-catalyst accelerates the polymerisation but not the lifetime of the catalyst and leads to a mixture of polyethylene and polyketone. Addition of the Lewis base triphenylphosphane (PPh
3) completely suppresses the formation of polyethylene. The polymers formed were characterised by IR spectroscopy,
13C cross polarisation (CP) magic angle spinning (MAS) solid state NMR spectroscopy, differential scanning calorimetry (DSC) and size exclusion chromatography (SEC).
The influence of different heteroaryl and functionalized aryl substituents on the electron-donating ability and basicity of the phosphorus atoms in heteroaryl phosphines and diphosphines has been ...determined by the use of the direct 1JPSe coupling constants of the corresponding selenides. The generality of the use of 31P-77Se spin-spin coupling constants as probe for the basicity of phosphines is discussed as well as the scope and limits of this concept. GRAPHICAL ABSTRACT image omitted
The influence of different heteroaryl and functionalized aryl substituents on the electron-donating ability and basicity of the phosphorus atoms in heteroaryl phosphines and diphosphines has been ...determined by the use of the direct
1
J
PSe
coupling constants of the corresponding selenides. The generality of the use of
31
P-
77
Se spin-spin coupling constants as probe for the basicity of phosphines is discussed as well as the scope and limits of this concept.
GRAPHICAL ABSTRACT
Planar chiral and achiral arenido(triphenylphosphane)nickel(II) complexes (arenido = mesitylenido, 2-toluenido) comprising electronically delocalised N,O chelating ligands were studied by
1
H and
19
...F NMR using 1D and 2D techniques. Results from complexes and corresponding ligands are discussed in the light of molecular structures obtained from X-ray diffraction.
GRAPHICAL ABSTRACT
The well-known tetradentate ligand 1,2-bis(pyridine-2-carboxamido)benzenate(2−), (bpb)2-, and its 4,5-dichloro analogue, (bpc)2-, are shown to be “noninnocent” ligands in the sense that in ...coordination compounds they can exist in their radical one- and diamagnetic two-electron-oxidized forms (bpbox1)- and (bpbox2)0 (and (bpcox1)- and (bpcox2)0), respectively. Photolysis of high-spin (n-Bu)4NFeIII(bpb)(N3)2 and its (bpc)2- analogue in acetone solution at room temperature generates the diamagnetic dinuclear complex (n-Bu)4NFeIV 2(μ-N)(bpb)2(N3)2 and its (bpc)2- analogue; the corresponding cyano complex (n-Bu)4NFeIV 2(μ-N)(bpb)2(CN)2 has been prepared via N3 - substitution by CN-. Photolysis in frozen acetonitrile solution produces a low-spin ferric species (S = 1/2) which presumably is FeIII(bpbox2)(N)(N3)-, as has been established by EPR and Mössbauer spectroscopy. The mononuclear complexes (n-Bu)4NFeIII(bpb)(CN2) (low spin), Et4NCoIII(bpb)(CN)2 and NaCoIII(bpc)(CN)2·3CH3OH can be electrochemically or chemically one-electron-oxidized to give FeIII(bpbox1)(CN)20 (S = 0), CoIII(bpbox1)(CN)20 (S = 1/2), and CoIII(bpcox1)(CN)20 (S = 1/2). All complexes have been characterized by UV−vis, EPR, and Mössbauer spectroscopy, and their electro- and magnetochemistries have been studied. The crystal structures of (n-Bu)4NFeIII(bpb)(N3)2·1/2C6H5CH3, NaFeIII(bpb)(CN)2, NaCoIII(bpc)(CN)2·3CH3OH, (n-Bu)4NFeIV 2(μ-N)(bpb)2(CN)2, and (n-Bu)4NFeIV 2(μ-N)(bpb)(N3)2 have been determined by single-crystal X-ray diffraction.
