324767-02-4Relevant academic research and scientific papers
Coordination chemistry of SCS Pd(II) pincer systems
Van Manen, Henk-Jan,Nakashima, Kazuaki,Shinkai, Seiji,Kooijman, Huub,Spek, Anthony L.,Van Veggel, Frank C. J. M.,Reinhoudt, David N.
, p. 2533 - 2540 (2000)
We have studied the coordination of substituted pyridines, and phosphorus- and sulfur-containing ligands to an SCS Pd(II) pincer system. These ligands coordinate to Pd(II) (trans to the cyclopalladated awl group) by quantitative substitution of the labile acetonitrile ligand in complex 1. Competition experiments showed that both electronic and steric effects influence the strength of coordination to the Pd(II) pincer of the substituted pyridines. A quantitative analysis of the substituent effect was achieved by a Hammett correlation. Phosphorus-containing ligands also coordinate to this SCS Pd(II) motif, as evidenced by NMR spectroscopy and single-crystal X-ray diffraction studies. They are much stronger ligands than the pyridines. The coordination strength of the thioureas falls in between those of the pyridines and phosphanes/phosphites. Our results lead therefore to the following order of ligand strength towards Pd(II) in SCS Pd(II) pincers: PRa > P(OR)3 > N,N'-disubstituted thiourea > (substituted) pyridines > MeCN.
