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Published December 13, 2010 | Supplemental Material
Journal Article Open

A Novel Bis(phosphido)pyridine [PNP]^(2−) Pincer Ligand and Its Potassium and Bis(dimethylamido)zirconium(IV) Complexes


A novel PNP bis(secondary phosphine)pyridine pincer ligand, 2,6-bis(2-(phenylphosphino)phenyl)pyridine, has been prepared in high yield, and the properties of the doubly deprotonated form as a ligand in K_4(PNP)_2(THF)_6 and (PNP)Zr(NMe_2)_2 have been investigated. The neutral PNP ligand has been isolated as a mixture of noninterconverting diastereomers, due to the presence of two chirogenic phosphorus atoms of the secondary phopshines, but coordination of the dianionic form to potassium and zirconium allows for isolation of a single diastereomer in near-quantitative yield. The structure of a bis(dimethylamido)zirconium(IV) derivative of the bis(phosphido)pyridine ligand and DFT calculations suggest that the phosphides do not π-bond to early transition metals, likely due to geometric strain and possibly orbital size mismatch between phosphorus and zirconium. As a result, the soft phosphides are prone to formation of insoluble oligomers with substantial bridging of the phosphido lone pairs to other zirconium centers.

Additional Information

© 2010 American Chemical Society. Received August 9, 2010. Publication Date (Web): November 3, 2010. We thank Taylor N. Lenton, Yuxiao Sun, and Ian A. Tonks for helpful discussions and for comparisons to their unpublished results. DFT calculations were carried out using the Molecular Graphics and Computation Facility, College of Chemistry, University of California, Berkeley, CA, with equipment support from NSF Grant CHE- 0233882. We gratefully acknowledge the support of the KAUST Center-In-Development at King Fahd University of Petroleum and Minerals (Dhahran, Saudi Arabia) and the USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-85ER13431). We thank Lawrence M. Henling and Michael W. Day of Caltech for mounting crystals and solving their structures. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (Grant CHE-0639094).

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Supplemental Material - om100775g_si_005.pdf


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