Regioselectivity and stereospecificity in (trimethylsilyl)methyl anion additions to the functionalized tungstenocene derivatives [W(.eta.-C5H4CH2CR:CH2)(.eta.-C5H5)Cl2] (R = H, CH3)

Synthesis and applications of chiral cyclopentadienylmetal complexes

“…The first example of an annulated chiral pentaalky-Icyclopentadiene has also been prepared from 2,2'-bis-(bromomethyl)-l,l'-binaphthyl (101) by the bisalkylation of an appropriately substituted cyclopentadiene (Scheme 22).45 Thus, the readily prepared trimethylcyclopentenone (102) which could be reduced and dehydrated to form 1,2,3-trimethylcyclopentadiene (103). Addition of the anion of 103 to dibromide 101 in the presence of excess potassium hydride gave spiroannulated cyclopentadiene 104 which could be thermolyzed to the desired pentaalkylcyclopentadiene 105 as a mixture of double bond isomers.…”

“…The synthesis of a similar chiral ansa-bis(2-indene) 183 having 1,1 '-binaphthyl-2,2'-dimethanediyl bridging two achiral 2-indenyl ligands is also shown in Scheme 44. In this synthesis 2,2,-bis(bromomethyl)-l,l'-binaphthyl (101), which is available in enantiomerically pure form, is reacted with deprotonated cyclohexylimine of 1-indanone 182 to yield after hydrolysis bis(l-indanone) 183 bridged at its 2-position. Reduction of the carbonyls to hydroxyl groups followed by acid-promoted elimination gave the l,l'-binaphthyl-2,2/-dimethanediyl bridged bis(2-indenyl) ligand 184.…”

Reactivity of the ansa-Bridged Metallocene Dichlorides [X(η5-C5H4)2]MCl2 (X = SiMe2, CMe2; M = Mo, W) toward Metallophosphide Anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). Formation of Heterobimetallic Complexes by Nucleophilic Substitution on a Cyclopentadienyl Ligand or on the Metal M

“…Tungstenocene derivatives with exocyclic boron or silyl substituents have been recently reported but their formation results from a ligand transfer from metal to the Cp ring. On the other hand, substituted tungstenocene complexes have been prepared by reaction of heteroanionic nucleophiles with the cationic derivative [Cp 2 W(SMe 2 )Br] + . 5a,b In this last case the positive metallic charge draining some electron density from the aromatic ligands may be responsible for the activation of the Cp rings. However, as also mentioned by Cooper, the neutral dichloride Cp 2 WCl 2 is able to undergo a ring substitution reaction when opposed to Grignard reagents; 5c,d MgCl 2 is postulated to promote the reaction by Lewis acid complexation of a chloride in Cp 2 WCl 2 .…”

“…On the other hand, substituted tungstenocene complexes have been prepared by reaction of heteroanionic nucleophiles with the cationic derivative [Cp 2 W(SMe 2 )Br] + . 5a,b In this last case the positive metallic charge draining some electron density from the aromatic ligands may be responsible for the activation of the Cp rings. However, as also mentioned by Cooper, the neutral dichloride Cp 2 WCl 2 is able to undergo a ring substitution reaction when opposed to Grignard reagents; 5c,d MgCl 2 is postulated to promote the reaction by Lewis acid complexation of a chloride in Cp 2 WCl 2 . We have recently shown that the dichlorides Cp 2 MCl 2 (M = Mo, W) display similar reactivity with metallophosphide anions [PPh 2 M‘(CO) x ] - .…”