A series of Ar-BIAN-based copper(I) complexes (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine) were synthesised and characterised by ¹H and ¹³C NMR spectroscopies, FT-IR spectroscopy, MALDI-TOF-MS spectrometry, cyclic voltammetry and single crystal X-ray diffraction. The bis-chelated complexes of general formula [Cu(Ar-BIAN)₂]BF₄ (where Ar = C₆H₅ (1), 4-iPrC₆H₄ (3), 2-iPrC₆H₄ (4)) were prepared by reaction of [Cu(NCMe)₄]BF₄ with two equivalents of the corresponding Ar-BIAN ligands, in dichloromethane, while the mono-chelated complexes of the type [Cu(Ar-BIAN)L₂]BF₄ (where Ar = 2,6-iPr₂C₆H₃, L = PhCN (6); Ar = 4-iPrC₆H₄, L = PPh₃ (7)) were readily accessible by treatment of [Cu(NCR)₄]BF₄ (R = Me, Ph) with one equivalent of the corresponding Ar-BIAN ligands in the absence or presence of two equivalents of PPh₃, in the same solvent. The structures of complexes 3, 4, 6 and 7 were obtained by single crystal X-ray diffraction, showing distorted tetrahedral geometries around the copper centres in all cases. The electrochemical studies of these complexes and of the already reported [Cu(2,4,6-Me₃C₆H₂-BIAN)₂]BF₄ (2) and [Cu(2,6-iPr₂C₆H₃-BIAN)(NCMe)₂] (5), demonstrated that the bis-chelated complexes 1–4 undergo a reversible one-electron reduction or oxidation processes on copper, while the mono-chelated complexes 5–7 show a partially reversible oxidation and an irreversible reduction feature. Both kinds of (Ar-BIAN)copper(I) complexes are active catalysts for the copper(I)-catalysed azide–alkyne cycloaddition reaction (CuAAC). Complex 7, bearing PPh₃ ligands, exhibits the highest catalytic activity, which is comparable with that of the typical CuSO₄–sodium ascorbate catalyst system.

Rhodium complexes modified by simple trialkylphosphines can be used to carry out homogeneous hydroformylation in supercritical carbon dioxide (scCO₂). The catalyst derived from PEt₃ is more active and slightly more selective for the linear products in scCO₂ than in toluene, and under the same reaction conditions [100°C, 40 bar of CO/H₂ (1∶1)] P(OPrⁱ)₃ is also an effective ligand giving good catalyst solubility and activity. Other ligands such as PPh₃, POct₃, PCy₃, and P(4-C₆H₄Bu^t)₃ are less effective because of the low solubility of their rhodium complexes in scCO₂. P(4-C₆H₄SiMe₃)_nPh_3−n (n = 3 or 1) and P(OPh)₃ impart activity despite their complexes only being poorly soluble in scCO₂. Under subcritical conditions, using PEt₃ as the ligand, C7-alcohols from hydrogenation of the first formed aldehydes are the main products whilst above a total pressure of 200 bar, where the solution remains supercritical (monophasic) throughout the reaction, aldehydes are obtained with 97% selectivity. High pressure IR studies in scCO₂ using PEt₃ as the ligand are reported.

The P,O-type phosphinophenol proligands (1·H, 2-PPh₂-4-Me-6-Me-C₆H₂OH; 2·H, 2-PPh₂-4-Me-6-^tBu-C₆H₂OH) readily react with one equiv. of ZnEt₂ to afford in high yields the corresponding Zn(II)-ethyl dimers of the type [(κ²-P,O)Zn-Et]₂ (3 and 4) with two μ-O_Ph bridging oxygens connecting the two Zn(II) centers, as determined by X-ray diffraction (XRD) studies in the case of 3. Based on diffusion-ordered NMR spectroscopy (DOSY), both species 3 and 4 retain their dimeric structures in solution. The alcoholysis reaction of Zn(II) alkyls 3 and 4 with BnOH led to the high yield formation of the corresponding Zn(II) benzyloxide species [(κ²-P,O)Zn-OBn]₂ (5 and 6), isolated in a pure form as colorless solids. The centrosymmetric and dimeric nature of Zn(II) alkoxides 5 and 6 in solution was deduced from DOSY NMR experiments and multinuclear NMR data. Though the heteroleptic species 5 is stable in solution, its analogue 6 is instable in CH₂Cl₂ solution at room temperature to slowly decompose to the corresponding homoleptic species 8via the transient formation of (κ²-P,O)₂Zn₂(μ-OBn)(μ–κ¹:κ¹-P,O) (6′). Crystallization of compound 6 led to crystals of 6′, as established by XRD analysis. The reaction of ZnEt₂ with two equiv. of 1·H and 2·H allowed access to the corresponding homoleptic species of the type [Zn(P,O)₂] (7 and 8). All gathered data are consistent with compound 7 being a dinuclear species in the solid state and in solution. Data for species 8, which bears a sterically demanding P,O-ligand, are consistent with a mononuclear species in solution. The Zn(II) alkoxide species 5 and the [Zn(P,O)₂]-type compounds 7 and 8 were evaluated as initiators of the ring-opening polymerization (ROP) of lactide (LA), ε-caprolactone (ε-CL) and trimethylene carbonate (TMC). Species 5 is a well-behaved ROP initiator for the homo-, co- and ter-polymerization of all three monomers with the production of narrow disperse materials under living and immortal conditions. Though species 7 and 8 are ROP inactive on their own, they readily polymerize LA in the presence of a nucleophile such as BnOH to produce narrow disperse PLA, presumably via an activated-monomer ROP mechanism.

Zinc alkyl cations supported by N,N-BIAN-type bidentate ligands were found to be highly active in the immortal ROP of ε-caprolactone to yield narrowly disperse and chain length-controlled poly(ε-caprolactone), whether in solution or bulk polymerization conditions.