Cyclopentadienyls phosphine substitution

Perhaps the most versatile approach to substituted cyclopentadienyl phosphines has been described in a series of reports by Kauffmann et aL concerning the chemistry of a spiro-cycloheptadiene. This derivative, which apparently can be easily prepared from cyclopentadiene and ethy-lenedibromide, reacts with a range of lithiated ligand precursors. This route provides access to a wide range of relatively complex hybrid ligands. 

The fourth chapter gives a comprehensive review about catalyzed hydroamina-tions of carbon carbon multiple bond systems from the beginning of this century to the state-of-the-art today. As was mentioned above, the direct - and whenever possible stereoselective - addition of amines to unsaturated hydrocarbons is one of the shortest routes to produce (chiral) amines. Provided that a catalyst of sufficient activity and stabihty can be found, this heterofunctionalization reaction could compete with classical substitution chemistry and is of high industrial interest. As the authors J. J. Bmnet and D. Neibecker show in their contribution, almost any transition metal salt has been subjected to this reaction and numerous reaction conditions were tested. However, although considerable progress has been made and enantios-electivites of 95% could be reached, all catalytic systems known to date suffer from low activity (TOP < 500 h ) or/and low stability. The most effective systems are represented by some iridium phosphine or cyclopentadienyl samarium complexes. 

A number of molecular mechanics studies of metal-cyclopentadienyl complexes have been reported recently. The systems studied include linear metallocenes (in particular ferrocene), ferrocene derivatives (such as complexes with substituted cy-clopentadienyl ligands, bis(fulvalene)diiron complexes, ferrocenophanes and mixed-ligand complexes with carbonyls and phosphines), and nonlinear cyclopentadienyl complexes 8,153,221 231]. 

In contrast to the inertness of bisalkynebisdithiocarbamate complexes, alkyne displacement from bisalkyne cyclopentadienyl derivatives is common. An extensive series of cationic [CpMo(CO)L(RC=CR)][BF4] complexes has been prepared from [CpMo(CO)(RC=CR)2][BF4] reagents by substitution of one of the coordinated alkynes [Eq. (19)] (72). Reaction of the carbonyl reagent with phosphines occurs smoothly at room temperature in methylene chloride to form monoalkyne products in high yields... 

Thermolysis of ()) -cyclopentadienyl)bis(neopentyl)(tri-methylphosphine)vanadium(I) (82) in the presence of 1,2-bis(dimethylphosphuio)ethane leads to the formation of the Schrock-type see Schrock-type Carbene Complexes) alkylidene vanadium complex (83), which is supported by X-ray crystallographic analysis (Scheme 45). " The imido vanadium complex (84) is converted to the corresponding alkylidene complex (86) on treatment with ben-zylidene(triphenyl)phosphorane (85) via substitution of the phosphine ligand (Scheme 46). ... 

Most catalysts that have been developed for asymmetric catalysis contain chiral C2-synimetric bisphosphines [7], The development of chiral ferrocenylphos-phines ventures away from this conventional wisdom. Chirality in this class of ligands can result from planar chirality due to 1,2-unsymmetrically ferrocene structure as well as from various chiral substituents. Two classes of ferroccnyldi-phosphines exist two phosphino groups substituted at the 1,1 -position about the ferrocene backbone (46) and both phosphino groups contained within a single cyclopentadienyl ring of ferrocene (4) [9]. 

Me3SiPPh2 assists in the insertion of CO into the Mn-R bond or RMn(CO)5 (R = alkyl or aryl) followed by silyl migration to oxygen. With Mn(CO)5H, however, only cis-substitution by the phosphine occurs, while with the cyclopentadienyl metal tricarbonyl hydrides, silylation occurs at the metal (Scheme 23)92. 

Bis(7T-cyclopentadienyl)zirconium moieties are presumed to be bridged by dialkyl-substituted phosphines in the products [Cp-2MPR2]2, obtained by the reaction of (7r-Cp)2ZrX2 with LiPR.2 (R = ethyl or butyl) in THF. The ethyl compound was obtained in a 71% yield of red-brown crystals which melt at 280°-282°C (dec.), and the butyl compound was obtained in a 59% yield of red-brown crystals which melt at 238°-240°C (dec.). Both compounds are sensitive to air and moisture. 

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