142457-87-2Relevant academic research and scientific papers
Synthesis, substitution, and isomerization reactions of trans-Re(CO)4LX (L = group 15 donor ligands; X = Br, I)
Ingham, Wayne L.,Coville, Nell J.
, p. 2551 - 2558 (2008/10/08)
The cleavage of Re2(CO)8L2 with X2 (X = I, L = PPh3, P(OMe)Ph2, P(OMe)3, P(OMe)2Ph, PMePh2, PMe2Ph, P(OPh)3, P(O-o-tol)3, P(OiPr)3, P(CH2C6H5)3; X = Br, L = PPh3, P(OMe)3, P(OMe)2Ph, PMe2Ph, P(OPh)3, P(CH2C6H5)3) in CH2Cl2 gives trans-Re(CO)4LX in yields between 20% and 50% as well as cis-Re(CO)4LX (>50%). Reactions of Re2(CO)9L with Br2, by contrast, gave only cis-Re(CO)4LBr and Re(CO)5Br, while reactions of Re2(CO)9PBz3 (Bz = CH2C6H5) with I2 gave Re(CO)5I as well as a mixture of cis- and trans-Re(CO)4PBz3I (ratio 72:28). The PBz3-containing product ratio could be modified by addition of I-(35:65 isomer ratio) and Br- (15:85, cis-trans ratio; product contained mixture of Re(CO)4PBz3I and Re(CO)4PBz3Br). The data for the cleavage reactions of Re2(CO)10-nLn (n = 1, 2) can be explained by an electrophilic attack of halogen, followed by two competing pathways (concerted, associative) involving attack of the nucleophile. It is predicted that in the total product spectrum (Re(CO)5X, Re(CO)4LX) that a maximum of 50% trans-Re(CO)4LX can be obtained by the halogen cleavage route. An IR kinetic investigation of the trans- to cis-Re(CO)4LX isomerization reaction is consistent with an intramolecular rearrangement process that is influenced by the halide (I 3 3 ～ P(OPh)3 ～ PMe2Ph 2 ～ PPh3 iPr)3 3). Reaction of trans-Re(CO)4PBz3I with L (L = P(OPh)3, t-BuNC) at 100°C in C6D6 revealed that isomerization (60%) was more rapid than substitution (3NO/CH3CN or PdO/t-BuNC gave product ratios of cis-and trans-Re(CO)3(PBz3)LI (L = CH3CN, t-BuNC) that were consistent with substitution preceding isomerization. The Re-CO bonds in trans-Re(CO)4PBz3I are less prone to cleavage than equivalent cis Re-CO bonds in cis-Re(CO)4PBz3I.
