107474-24-8Relevant articles and documents
Study of the amination reaction of the coordinated cyclopentadienyl ring in (η5-Cp)FeL1L2X derivatives. Crystal and molecular structure of (η5-C5H4NEt 2)Fe(CO)[PhP(OEt)2]Br
Brun, Pierre,Vierling, Pierre,Riess, Jean G.,Le Borgne, Guy
, p. 1032 - 1040 (2008/10/08)
The influence of the nature of X, L1, L2, and the NR2 anions on the reaction between LiNR2 and (η5Cp)FeL1L2X derivatives 6 (L1 = CO, L2 = PR3; L1 = L2 = PR3; X = Cl, Br) has been investigated in order to explore the extent and potential in synthesis of the amination reaction of the coordinated cyclopentadienyl ring in 6. A rather complex situation was found with up to five different reaction products isolated or identified: the main derivatives that formed were the aminated adducts (η5-C5H4NR2)FeL 1L2X (9) and (η5-C5H4NR2)FeL 1L2H (10) and the diiron species [(η5-C5H5)Fe(L)(μ-CO)]2 (13). The results show indeed that there is a significant influence of the nature of the halogen X, the ligands L1 and L2, and the amide anions NR2- on the amination process. (i) It leads to C5H4NR2 adducts only when R ≠ H. (ii) Much higher yields in aminated derivatives 9 and/or 10 are obtained starting from the (η5-Cp)FeL(CO)X or (η5-Cp)FeL1L2X derivatives than from the (η5-Cp)Fe(CO)2X adducts while, on electronic grounds, the latter were expected to be the most suitable candidates: this illustrates the prominent role played by the steric effects of the ligands. (iii) The π-acceptor character of the ligand L plays, however, an important role and favors the amination process: in the case of (η5-Cp)FeL(CO)X derivatives, when L = P(OPh)3 or PhP(OR)2, C5H4NR2 compounds (9 and 10) are obtained in 57-88% yields while for the bulkier PPh3 ligand the yield is only of 31%. This effect is even more drastic in the case of (η5-Cp)FeL2Br derivatives: while, for L = PhP(OEt)2, the amination reaction occurs in good yield (74%), no aminated adduct was detected for L2 = dppe which is a better donating ligand than PhP(OEt)2. (iv) The brominated derivatives 6 are much better starting materials than their chlorinated analogues. Compound 9d, (η5-C5H2NEt 2)Fe(CO)[PhP-(OEt)2]Br (C20H29BrFeNO3P), crystallizes in the triclinic space group P1 with a = 10.926 (3) A?, b = 11.407 (2) A?, c = 10.399 (2) A?, α = 106.53 (1)°, β = 109.40 (2)°, γ = 99.35 (2)°, and Z = 2. Its structure shows the nitrogen atom to be coplanar with its sustituents; the Cp ring lies approximately in the same plane; the N-C2(Cp) bond is short (1.332 (4) A?) and the C2-Fe distance long (2.304 (3) A?).
