62263-67-6Relevant articles and documents
Insights into the stability and structures of phosphine-boranes and their α-metalated derivatives
Izod, Keith,Wills, Corinne,Anderson, Emma,Harrington, Ross W.,Probert, Michael R.
, p. 5283 - 5294 (2014)
The reaction between iPr2PCl and Ph2P(BH3)CH2Li gives the mixed phosphine/phosphine-borane Ph2P(BH3)CH2PiPr2 (1a) in good yield. Thermolysis of 1a leads to borane migration and the formation of Ph2PCH2P(BH3)iPr2 (2a) along with small amounts of Ph2P(BH3)CH2P(BH3)iPr2 (3a) and Ph2PCH2PiPr2 (4a). Compound 3a may be synthesized directly from the reaction of 1a with BH3·SMe2, while 4a can be prepared cleanly by heating 1a in methanol under reflux. Kinetic studies on the conversion of 1a to 2a reveal the reaction to be apparently first order in 1a, suggesting a dissociative process, and yield the activation parameters δH∥ = 63 ± 8 kJ mol-1, δS∥ = -145 ± 24 J K-1 mol-1, and δG∥ = 106 ± 8 kJ mol-1, the negative entropy of activation conversely suggesting an associative process. DFT studies suggest that concerted migration of borane within a molecule of 1a is disfavored, but that both the dissociative and associative mechanisms for borane migration operate simultaneously. Metalation of 1a-4a with nBuLi in the presence of tmeda gives the complexes [{Ph2P(BH3)}CHPiPr2]Li(tmeda) (1b), [Ph2PCH{P(BH3)iPr2}]Li(tmeda) (2b), [{Ph2P(BH3)}CH{P(BH3)iPr2}]Li(tmeda) (3b), and [Ph2PCHPiPr2]Li(tmeda) (4b), respectively, which adopt similar structures in the solid state. Analysis of the crystal structures suggests that the phosphine-borane groups stabilize the adjacent charge to a greater extent than the phosphine groups. This is supported by DFT calculations, which show that the greatest delocalization of negative charge from the carbanion is into the P-C(Ph) or P-C(Pr) σ-orbitals of the phosphine-borane substituents.
A new synthetic route to ligands of the general composition R2PCH2ER′2 (E = P, As) and some rhodium complexes derived thereof
Wolf, Justin,Manger, Matthias,Schmidt, Ulrich,Fries, Guido,Barth, Dietmar,Weberndoerfer, Birgit,Vicic, David A.,Jones, William D.,Werner, Helmut
, p. 1867 - 1875 (2007/10/03)
Symmetrical and unsymmetrical bis(phosphino)methanes R2PCH2PR′2 (8-16) as well as the arsino(phosphino) analogues R′2AsCH2PR2 (21-25) with bulky alkyl, cycloalkyl or aryl groups R and R′ were prepared from the stannylated phosphines R2PCH2SnR″3 (3-5, 6, 7) Via metalation with MeLi or PhLi in the presence of tetramethylethylenediamine and subsequent treatment with R′2PCl or R′2AsCl, respectively. Compound 25 [R′ = Cy, R = (R)-menthyl] is the first arsino(phosphino)methane which has been structurally characterized. The bis(phosphino)methanes R2PCH2PR2 (R = Pri 17, Cy 18) and R2PCH2PR′2 (12, 19, 20) were also obtained by thermal reaction of R2PCH2SnPh3 and the corresponding chlorophosphine R2PCl or R′2PCl in the absence of solvent. The bis(cyclooctene) derivative [RhCl(C8H14)2]2 26 reacted with excess Pri2PCH2PPri2 to give [Rh(κ2P,P′-Pri2PCH 2PPri2)2]Cl 27, while treatment of 26 with Ph2PCH2PPri2 yielded the chloro-bridged dimer [RhCl(κ2P,P′-Ph2PCH2PPr i2)]2 28. The reaction of the cationic species [Rh(C8H14)2(OCMe2) 2]PF6 29 with Cy2PCH2PPri2 in benzene or toluene afforded the half-sandwich-type complexes [(η6-C6H6)Rh(κ 2,P′-Cy2PCH2PPri 2)]PF6 30, [(η6-C6H5CH3)Rh(κ 2P,P′-Cy2PCH2PPri 2)]PF6 31, of which the latter was characterized by X-ray crystallography.
