The impact of P-substituents on the structures, spectroscopic properties, and reactivities of POCOP-type pincer complexes of nickel(ii)

Abstract

The room temperature reaction of NiBr(2)(NCCH(3))(x) with the pincer-type ligand POCHOP(Ph) gave the new pincer complex (POCOP(Ph))NiBr (1, POCOP(Ph) = κ(P), κ(C), κ(P)-2,6-{Ph(2)PO}(2)C(6)H(3)). Complex 1 reacts with AgX to give the analogous Ni-X derivatives (X = CN, 2; OSO(2)CF(3), 3; OC(O)CH(3), 4; ONO(2), 5), whereas complex 3 reacts with phenylacetylene and NEt(3) to give the Ni-CCPh derivative 6. On the other hand, reaction of 1 or 3 with RLi or RMgI did not afford the desired Ni-R derivatives, giving instead the corresponding iodo and hydroxo derivatives. Complexes 1-6 have been characterized by NMR, IR, and UV-Vis spectroscopy and X-ray crystallography. The solid state structural and IR data indicate that Ni-C(sp) interaction is dominated by ligand-to-metal σ-donation in 2 and 6. Cyclic voltammetry measurements indicate that complexes 3 and 4 display reversible redox behaviour (Ni(II)/Ni(III)); comparison of the E(0)(1/2) values for these complexes and their POCOP(i-Pr) analogues shows that both the X ligands and the P-substituent have a considerable impact on the ease of oxidation in this family of complexes.

The Reactivity of Mercapto Groups against Boron Hydrides in Pincer Ligated Nickel Mercapto Complexes

“…Similar 1 H NMR resonances and H‐P coupling constants were previously reported for other transition metal mercapto complexes ,. Generally, a tert ‐butyl group is more electron‐donating than an isopropyl group and a PCP pincer ligand is more electron rich than the corresponding POCOP pincer ligand ,,. It is supposed that the chemical shifts of the SH protons are influenced by the electronic nature of the pincer backbone.…”

On the P‐Coordinating Limit of NHC–Phosphenium Cations toward RhI Centers

“…The 31 P NMR chemical shift of 3 a (d p = + 142.4 ppm) is in the typical range for phosphonite compounds. [15] Whereas the 31 P NMR resonance of the phosphonite fragment of 3 b is www.chemeurj.org observed in the same range (d p = + 141.1 ppm, doublet, J PP = 65.8 Hz), the second resonance (d p = À17.4 ppm, doublet, J PP = 65.8 Hz) is in good agreement with the triarylphosphane fragment. The ionic nature of the products was indicated by a very low solubility in nonpolar solvents and by a deshielded 1 H NMR signal that corresponds to the Nmethyl substituent (d H = + 4.1 ppm; Scheme 2).…”

Charge Effects in PCP Pincer Complexes of NiII bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis

“…This family of complexes features 5‐ and 6‐membered fused metallacycles and bite angles (P11‐Ni‐P12) that are much greater than in their POCOP analogues featuring two fused 5‐membered metallacycles (ca. 170–176° vs. 164°) 21. The bite angles in [( R PIMCOP R′ )NiBr] are also influenced by the P‐ substituents, being roughly 6–7° wider in the structures of 3 b and 3 c bearing the bulkier i Pr 2 P moieties.…”

“…170-1768 vs. 1648). [21] The bite anglesin[ ( R PIMCOP R' )NiBr] are also influenced by the P-substituents,b eing roughly6 -78 wider in the structures of 3b and 3c bearing the bulkier iPr 2 Pm oieties. Steric factors appear to have less influence over bond lengths, but the NiÀPd istances in 3a and 3b (R = R':2 .132-2.134a nd 2.168-2.169)a re significantly shorter than those in 3c (R ¼ 6 R': 2.138 and 2.199 ).…”