Tris-tert-butyl-phosphane

Heck and Suzuki type couplings have been described by Fu [2] et al. The reaction of chlorobenzene and styrene in refluxing dioxane in the presence of [Pd2(dba)3 ] and the electron rich tri-tert.-butyl-phosphane [eq. (a)] gives rise to trans-stilbene in 83% yield. Besides the choice of the ligand - aryl phosphanes, tri-n-butyl-phosphane or tri-cyclo-hexyl-phosphane show no conversion - the base is also crucial for success. Cesium carbonate gives the best results, although the cheaper potassium phosphate gives comparable yields. 

Under the same conditions the sterically more demanding 2-chlorotoluene is coupled in 70% yield. However longer reaction times are necessary. Acceptor- as well as donor-substituents are tolerated under these conditions. Tri-tert.-butyl-phosphane is the ligand of choice in Suzuki-couplings [3] as well 2-chlorotoluene reacts with 2-methyl-phenylboronic acid to 2,2 -disubstituted biphenyl in 87% yield [eq. (b)]. 

Phosphane Chloro-(2.4.6-tri-tert-butyl-phenyl)-trifluoromcthyl-EI0b,. 660 (Li PCl-CFj)... 

The Vc-(N)-p couplings measured by Herberhold et for a series of tri(tert-butyl)plumbyl-phosphanes allowed the authors a unequivocal elucidation of the preferred conformation of the amino group with respect to an axis representing the assumed orientation of the lone pair of electrons at the phosphorus atom. A large and positive coupling corresponds to the syn-orientation of the N-C bond with respect to the lone pair of electrons, and a small and of either sign Vc-n-p coupling reflects the anti orientation. 

Organolead-phosphorus compounds are highly attractive from the NMR point of view, considering the presence of the spin-1/2 nuclei H, l3C, 3IP, and 207Pb in the same molecule. This has been used in a study focusing on tris(tert-butyl)plumbyl phosphanes.91 Some selected data for 56-59 are given below. 

The cyclotrimerization of (2,2-dimethylpropylidyne)phosphane (la) in the presence of the (cyclooctatetraene)hafnium complex 9 affords the hafnium complex 10 in 83% yield treatment of the latter with hexachloroethane then furnishes 2,4,6-tri-tert-butyl-l,3,5-triphosphinine (11a) through expulsion of the metal fragment [14]. 

Triphenylphosphan(3,5-di-tert.-butyl-2-hydroxy-phenylimid) Tris-[4-methyl-phenyl]-phosphan-(3,5-di-tert.-butyl-2-hydroxy-phenylimid) Tris-[4-methoxy-phenyl -phosphan-3,5-di-tert.-butyl-2-hydroxy-phenylimid) Tris-[4-fluor-phenyl]-phosphan-(3,5-di-tert.-butyl-2-hydroxy-phenyUmid)... 

Phosphan tert.-Butyl-(2,2-dimethyl-1 -tri methylsilyloxy-propy liden)-El. 43 [R — P(SiR3)2 +... 

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