Palladacycle versus coordination complex of palladium(II) with a bulky organophosphorus (P,N) ligand: Application in catalysis of allylation of aldehydes

Palladacyclic complex 1 [Pd(L1)Cl] [L1: anthracene-9-yl-CH = N(CH2)(2)-PPh2 behaving as (P, N, C-) ligand] has been prepared, and characterized using multi-nuclei NMR spectroscopic, high resolution mass spectrometric (HRMS) and single-crystal X-ray diffraction (SC-XRD) techniques. This palladacycle 1 and the 2 [i.e., Pd(L1)Cl-2, a square planar Pd(II) complex of the same ligand] have anthracene core, imine functionality and P,N donors. Both the 1 and 2 have been explored as potential catalysts for allylation of aldehydes with allyltributylstannnane. Both the complexes show good efficiency towards this C-C coupling reaction. Various aldehydes such as 4-bromobenzaldehyde, 4-chlorobenzaldehyde, 2-bromobenzaldehyde, 2-chlorobenzaldehyde, 4-methoxybenzaldehyde, 4-methylbenzal dehyde, 4-nitrobenzaldehyde pyridine-2-carboxaldehyde and furfural have been explored for this reaction. Effect of presence of Pd-C bond is noticed on the catalytic performance. The palladacyclic complex 1 is more efficient than coordination complex 2 as the Pd-C bond of metallacyclic complex increases the rate of dissociation of Pd-Cl bond and therefore helping in easy participation and increased efficiency of complex 1 in catalysis.

Automated summary

In this study, a palladacyclic complex 1 with anthracene core, imine functionality, and P,N donors has been synthesized and characterized. It shows good catalytic efficiency in the allylation of aldehydes with allyltributylstannane.