Zirconocene 1-butene complex

Heterobimetallic complexes of zirconium and molybdenum have also been prepared from zirconocene olefin complexes. Displacement of 1-butene from the phosphine-substituted zirconocene 1-butene complex, (775-C5H4PPh2)2Zr( 72-CH2=CHCH2CH3) 107, by addition of /< //-butyl isonitrile in the presence of Mo(CO)4(norbornadiene) furnishes the formal zirconium(n)-molybdenum(0) compound, 108 (Equation (4)).47... 

A similar, albeit more complex, reactivity manifold is reported for the formation of the Negishi reagent starting from bis( -butyl)zirconocene, which inter alia decomposes to give the putative zirconocene butene complex. Among the compounds identified in this mixture is a labile 2-methylzirconacyclobutane complex <19970M1452>. 

The transient zirconocene butene complex, 105, has proved to be useful in a number of organic transformations. For example, butene substitution of zirconocene alkene complexes with alkoxy-substituted olefins results in /3-alkoxide elimination to furnish the zirconocene alkoxy compounds (R = Me, 123 R = Bnz, 124) (Scheme 16).50,51 Addition of propargyl alcohols to the zirconocene butene complex, 105, affords homoallylic alcohols. These reactions are of limited utility owing to the lack of stereoselectivity or formation of multiple products. Positioning the alkoxide functional group further down the hydrocarbyl chain allows synthesis of cyclopropanes, though mixtures of the carbocycle and alkene products are obtained in some cases (Scheme 16).52... 

In most cases, complexes of primary alkyl ligands are more stable than the isomeric complexes of secondary or tertiary alkyl ligands. For example, Reger has shown that the secondary butyl iron complex in Equation 3.18 isomerizes to the corresponding primary n-butyl complex, and that the isopropyl palladium complex in Equation 3.19 isomerizes to the more stable -propyl isomer. Likewise, secondary zirconocene alkyl complexes isomerize to the linear isomers (Equation 320), as shown many years ago by Schwartz, and Labinger and Bercaw have recently shown that the sec-butyl complex of zirconocene, generated by the hydrozirconation of cis-2-butene, isomerizes in several hours to the corresponding n-butyl complex. ... 

Zirconocene alkene complexes 29 are readily prepared by the p-hydride activation route from dialkyl zirconocenes 28 or methyl alkyl zirconocenes 27 (Scheme 5.10). It is also possible to prepare the zirconocene complexes of ethene, styrene, and, to a lesser extent, vinyltrimethylsilane by displacement of the weakly bound 1-butene ligand from 4. ... 

The use of a zirconium complex (dibutylzirconocene, — 78 °C to rt, 2 h) to induce intramolecular co-cyclization of A-methyl-5-azanona-l,8-diene to an intermediate zirconacycle was a key step in a new azepane synthetic route hydrolysis (MeOH, aq. NaHC03) of this intermediate then realized the trans- 1,4,5-trimethylazepane in 75% yield the active reagent for the initial cyclization was zirconocene (1-butene). The overall transformation represents a type d ring construction process <2006SL3439>. This synthetically versatile process is also applicable to aza eneyne and aza diyne precursors as well as benz-fused analogues. 

Compound (CsH4SiMe2NBut)TiCl2 has been synthesized and used as pre-catalyst for ethylene polymerization. The activities and the properties of the polymers have been compared to similar zirconium and hafnium derivatives.720 The consequences of anion-cation interactions on the activity of GGG group 4 metal complexes in olefin polymerizations have been explored for a series of zirconocene derivatives as well as the cationic species [(C5Me4SiMe2NBut)TiMe]+ with the sterically congested tris(perfluorobiphenyl)fluoroaluminate as the counteranion.721 The co-polymerization of ethylene and 1-butene by (CsMe iMe Bu TiC in the presence of... 

Codimers with alkynes can also be obtained from 1,2-diphenylcyclopropene when the trimethylphosphane-stabilized metallocene complexes 20 (M = Ti, Zr) of this cyclopropene derivative are used as substrates. The titanocene complex is prepared from bis(>/ -cyclopen-tadienyl)bis(trimethylphosphane)titanium (18), while the zirconocene complex is most conveniently formed from (f7 -but-l-ene)bis(f7 -cyclopentadienyl)(trimethylphosphane)zirconium (19) via a substitution reaction of the butene ligand. When 20 (M = Ti) is reacted with but-2-yne, the titanacycle 21 can be isolated as blue crystals in 71% yield. The zirconacycle 21 (M = Zr) is obtained in 78% yield as an orange powder. ... 

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. 

---