Phosphine complexes of zirconium and hafnium. Synthesis, structure, and fluxional behavior of the trimethyl derivatives MMe3[N(SiMe2CH2PR2)2] (R = Me, CHMe2, CMe3). Evidence for a bicapped-tetrahedral geometry

Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

“…The 1 H and 13 C chemical shifts exhibited by the HfeMe groups in 4 are comparable to those previously reported in similar compounds. For example, Fryzuk's ( Si PNP)HfMe 3 compounds (E) resonated in their 1 H NMR spectra in the 0.5e0.9 ppm range, depending on the nature of the alkyl group on P (no 13 C NMR data reported) [17]. The 13 C NMR chemical shift of ( t Bu 2 C 5 H 3 )HfMe 3 was found to be 57.3 ppm by Royo et al [18].…”

“…The coordination environment about Hf in 5 can be described similarly, although it is not superimposable with (PNP)HfMe 3 . Fryzuk et al analyzed the structure of the closely related ( Si PNP Me )HfMe 3 as a bicapped tetrahedron, with the two neutral P donors capping the faces of the NHfMe 3 tetrahedron [17]. This description is less apt for (PNP)MMe 3 (M ¼ Zr or Hf) because the requisite angles deviate to a significantly greater degree from the idealized bicapped tetrahedron.…”

“…The HfeMe bond distances in Fryzuk's ( Si PNP Me )HfMe 3 [17] and (P 2 N 2 )HfMe 2 [26] are in the 2.24e2.27 Å range, and the ZreMe bond distances in our (PNP)ZrMe 3 are in the 2.25e2.29 Å range [11]. Scott and Lippard reported a series of Zr and Hf bis(trimethylsilylmethyl) complexes supported by N 4 dianionic tropocoronand ligands with MeC bonds ranging from 2.24 to 2.35 Å [21].…”

“…Zr and Hf complexes of Si PNP have been reported, including polyalkyls (E and F, Fig. 1) [17], but not alkylidenes.…”

The 1992 Alcan Award Lecture Excursions around the periodic table: ligand design in inorganic chemistry

“…Hugh did find that hydride complexes of hafnium(1V) could be prepared (24) doctoral fellow, Dr. Axel Westerhaus, solved a lot of our problems in this area by coming up with straightforward syntheses of monoligand staring materials for Zr(1V) and Hf(1V) with a variety of substituents at phosphorus (25); this is outlined in Scheme 8. These monoligand derivatives turned out to be exceedingly versatile as we were able to prepare dinuclear hydride complexes (26), derivatives containing the r14-butadiene moiety (27,28), and trimethyl complexes of Zr and Hf (29). Tim Haddad prepared the r14-butadiene complexes as part of his M.Sc.…”