Reactions of (η5-C5H5)2Tir compounds with organic cyanides

Competition of Nucleophilic Aromatic Substitution, σ‐Bond Metathesis, and syn Hydrometalation in Titanium(III)‐Catalyzed Hydrodefluorination of Arenes

“…[6q] Interestingly,t he hydrodebromination is catalytic althougho nly low turnover numbers (TONs) were observed; furthermore, there are no second HDF products as observed for 9,w hich indicates that the catalytic active species 1 is poisoned. Only low TON or stoichiometricH DF was observed for substrates with electron-donatingg roups 11 and 12 leading to the para-HDF products,r espectively (entries 13,15). Ac ompeting hydrosilylation (or hydrometalation)r eaction of 11 as described by Buchwald et al for reactions of imines with 1a or (S,S)-(ebthi)TiF 2 (ebthi = 1,2-ethylene-1,1'-bis(h 5 -tetrahydroindenyl)) and PhSiH 3 can be ruled out by 19 FNMR spectroscopy.…”

“…[12] Since the catalyst is very Lewis acidic,ita ppears plausible that it is captured by the donor function in 11 and 12 and thus nearly inactive.A dduct formation of titanocene(III)d erivatives with variouso rganic cyanides wasa lso reported by de Boer and Te uben. [13] To test this assumption, we added equimolar amounts of 11 to ac atalytic run of 5 (entry 14) under similar reaction conditions (cf. entry 2).…”

“…PathwayB:T S B Geometries (5, 6, 9, 11,1 2, 13) PathwayBleads either to ah ydrometalation intermediate (HM for 6,9,13)o razwitterionic (Meisenheimer-type) species ( 5,11,12)a nd the corresponding transition states (HM and S N Ar) differ significantly.F igure 5( left) displays as chematic view along the H-Tia xis, which illustrates the two different orientation modes of the substrates in the TS B .ACp-Cp tilting angle (a)o f4 2-448 is observedf or the HM transition state and 30-388 for the H-addition transition state (Figure5 and Table 3). Figure 5( middle and right) illustrates the view perpendicular to the C ortho ÀC ipso bond.…”

Frontier Elements: Connections with f-Elements

“…CO, CO2, CS2, isonitriles, nitriles, ketones, acetylenes). Most of the work has been published and the interested reader is referred to these publications for detailed information [5][6][7][8][9][10][11].…”

“…In the last decade organo-f-element chemistry has developed almost explosively. Especially organometallic compounds with carbocyclic ligands of the cyclopentadienyl type (Cp = η 5 -C5H5, Cp* =η 5 -C5(CH3)5, and other substituted cyclopentadienyls) have attracted a great deal of attention. This field now gives a clear picture of systematic investigations on the synthesis and reactivity of certain classes of compounds of both 4f-and 5f-elements.…”