6-Phenyl-2- zirconium complexes

The construction of a borole ring that is part of a metal complex from zirconium-coordinated 1,3-dienes and tris(pentafluorophenyl)borane has been recently introduced. Tris(pentafluoro-phenyl)borane is widely used as an activator of metallocene-based polymerization catalysts because of its resistance to aryl-transfer reactions, it acts as the boron source. The reaction utilizes the zwitterionic 14-electron bis(allyl)zirconium complexes 72 and 73 which are converted to the corresponding complexes 74 and 75 via activation of one of the C-H bonds of the B-CH2 moiety... 

Golub et al. have shown that zirconium(IV) and hafnium(IV) form eight-coordinate complexes in solution with NCS" alone or in the presence of DMF 329, 333). The compounds (Et4N)2[M(NCS)8] (M = Zr, Hf) both contain iV -thiocyanato groups, as determined by infrared studies, and are isomorphous 61). Benzyl phenyl arsinic acid has been used as an extractant and, unlike most systems, hafnium complexes are extracted better than zirconium complexes in the presence of NCS" 302). 

PCkHii, Phosphine, dimethylphenyl-, iron complex, 26 61 molybdenum complex, 27 11 osmium complex, 27 27 osmium-rhodium complex, 27 29 osmium-zirconium complex, 27 27 ruthenium complex, 26 273, 278 PC,H, Phosphine, ethylmethylphenyl-, lithium complex, 27 178 PCvH , Phosphorane, dimethylmethylene-phenyl-, uranium complex, 27 177... 

Stereoblock polypropylene is synthesized by unbridged metallocenes such as bis(neomenthyl)zirconium dichloride (7) with cyclopentadienyl or phenyl substituted indenyl ligands [55, 56]. The stereoblock length increases at lower polymerization temperatures. Products containing isotactic and atactic blocks are elastomeric if the isotactic block length is short. Rieger [57] obtained similar polypropylenes by bridged fluorenyl-substituted indenyl zirconium complexes. 

Chiral zirconocene complexes have also been studied as catalysts for the hydrogenation of nonfunctionalized olefins115. Using homogeneous Ziegler Natta-type catalyst systems derived from [ethylenebis(4,5.6,7-tetrahydro-l-indenyl)]zirconium complexes and methyl aluminoxane [A1(CH3)0] , 2-phenyl-l-butene was hydrogenated in 36% optical yield (20 bar H2, benzene, 25 °C). Under the same conditions, the reaction of styrene with D2 gave optically active 1,2-dideuteroethylbenzene with 65% ee. 

Monoanionic boratabenzene ligands are isoelectronic to cyclopentadienide anion and can be nsed to synthesize Zr equivalent metallocenes (eqnation 29). A more congested complex of 9-phenyl-9-borata-anthracene (C 1-synunetry) was obtained by a similar way. Mono and bis boratabenzene complexes can also be prepared by reaction of a nentral boratabenzene-PMes adduct with tetrabenzyl zirconium or hafnium. Boratabenzene ansa metallocenes with CH2-CH2 or Si(CH3)2 bridges as well as Cp-boratabenzene mixed complexes or CG complexes were synthesized. 

Hollis and coworkers reported also on a transmetalla-tion process from zirconium to rhodium. As illustrated in Scheme 33, imidazolium salt (209) reacted instantaneously with Zr(NMe2)4 to generate the biscarbene pincer (210) with orthometallation of the phenyl group. The biscarbene pincer was not isolated, but reacted with [Rh(COD)Cl]2. The Rh(III) complex (211) was isolated in equilibrium with the dimer (212). 

For these complexes, the rate of carbonylation increases rapidly with increasing tr-alkyl character. Thus, (5-cis-butadiene)ZrCp2 (5a) is carbony-lated 2.5 times faster than the zirconocene complex of 1,2,5,6-tetramethyl-3,4-bis(methylene)tricyclo[3.1.0.0 ] hexane (51) (ambient temperature and 1 bar CO pressure) taken as a standard. Introduction of methyl groups at the internal carbon centers C2/C3 of the diene chain increases the carbonylation rate by a factor of 5 with phenyl groups at these positions increasing the rate by a factor of 250 (Table VIII). The organometallic reaction products have yet to be isolated or completely identified. Ultimately, zirconium enolate complexes (20) are probably formed in these... 

Attaching peripheral chiral R auxiliary to the amido nitrogen creates Cj-chiral tripodal amido ligands for the synthesis of chiral metal complexes. For example, the chiral zirconium chloride complex 204, obtained from the salt metathesis approach involving the reaction of the lithium salt of the trianionic ligand with ZrGI4 in toluene, contains (A)-3,3-dimethyl-2-butyl group as chiral R auxiliary.172 The peripheral chiral R auxiliaries are (.S )-1 -phenyl ethyl and (R)-l-indanyl in chiral complexes 205 and 206, respectively.173... 

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