106419-07-2Relevant academic research and scientific papers
Synthesis and reactivity of cyclo-tetra(stibinophosphonium) tetracations: Redox and coordination chemistry of phosphine-antimony complexes
Chitnis, Saurabh S.,Robertson, Alasdair P. M.,Burford, Neil,Weigand, Jan J.,Fischer, Roland
, p. 2559 - 2574 (2015)
Reductive elimination of [R3PPR3]2+, [11(R)]2+, from the highly electrophilic SbIII centres in [(R3P)3Sb]3+, [8(R)]3+, gives SbI containing cations [(R3P)Sb]1+, [9(R)]1+, which assemble into frameworks identified as cyclo-tetra(stibinophosphonium) tetracations, [(R3P)4Sb4]4+, [10(R)]4+. A phosphine catalyzed mechanism is proposed for conversion of fluoroantimony complexes [(R3P)2SbF]2+, [7(R)]2+, to [10(R)]4+, and the characterization of key intermediates is presented. The results constitute evidence of a novel ligand activation pathway for phosphines in the coordination sphere of hard, electron deficient acceptors. Characterization of the associated reactants and products supports earlier, albeit less definitive, detection of analogous phosphine ligand activation in CuIII and TlIII complexes, demonstrating that these prototypical ligands can behave simultaneously as reducing agents and σ donors towards a variety of hard acceptors. The reactivity of the parent cyclo-tetra(stibinophosphonium) tetracation, [10(Me)]4+, is directed by high charge concentration and strong polarization of the P-Sb bonds. The former explains the observed facility for reductive elimination to yield elemental antimony and the latter enabled activation of P-Cl and P-H bonds to give phosphinophosphonium cations, [Me3PPR′2]1+, including the first example of an H-phosphinophosphonium, [(Me3P)P(H)R′]1+, and 2-phosphino-1,3-diphosphonium cations, [(Me3P)2PR′]2+. Exchange of a phosphine ligand in [10(Me)]4+ with [nacnac]1- gives [(Me3P)3Sb4(nacnac)]3+, [15(Me)]3+, and with dmap gives [(Me3P)3Sb4(dmap)]4+, [16]4+. The lability of P-Sb or Sb-Sb interactions in [10(Me)]4+ has also been illustrated by characterization of heteroleptically substituted derivatives featuring PMe3 and PEt3 ligands. This journal is
Pentadienyl-metal-phosphine chemistry. 9. The 2,4-dimethylpentadienyl-iron-trimethylphosphine reaction system
Bleeke, John R.,Hays, Mary K.
, p. 486 - 491 (2008/10/08)
The reaction of FeCl2(PMe3)2 with potassium 2,4-dimethylpentadienide-tetrahydrofuran (K+2,4-Me2pd-) can be directed into three separate manifolds by varying the ratio of K+2,4-Me2pd- to iron. Use of a 2:1 K+2,4-Me2pd-:Fe ratio leads to the production of (η5-2,4-Me2pd)(η3-2,4-Me 2pd)Fe(PMe3) (1) while a 1:1 K+2,4-Me2pd-:Fe ratio yields (η4-isopropenyltrimethylenemethyl)Fe(PMe3)3 (2) via a reaction sequence involving activation of a C-H bond in a 2,4-Me2pd methyl group. When the ratio of K+2,4-Me2pd-:Fe is reduced to 1:2, (η5-2,4-Me2Pd)Fe(PMe3)3 +FeCl3(PMe3)- (3) is produced. Single-crystal X-ray diffraction studies of both 2 and 3 have been carried out. Compound 2 crystallizes in the monoclinic space group P21/c with a = 8.878 (1) A?, b = 14.737 (4) A?, c = 16.689 (3) A?, β = 102.25 (1)°, V = 2129.5 (8) A?3, and Z = 4. The complex assumes an approximate octahedral geometry with C1, C3, and C6 of the isopropenyltrimethylenemethyl ligand (iTMM) and the three phosphine phosphorus atoms occupying the six coordination sites. The iTMM ligand exhibits an umbrella shape with C2 bent out of the C1/C3/C6 plane. Compound 3 crystallizes in the monoclinic space group C2/c with a = 18.442 (5) A?, b = 18.433 (5) A?, c = 17.875 (5) A?, β = 91.87 (2)°, V = 6073 (3) A?3, and Z = 8. The coordination geometry of the cation is approximately octahedral with C1, C3, and C5 of the 2,4-Me2pd ligand and P1, P2, and P3 of the PMe3 ligands occupying the six coordination sites. The anion of 3, FeCl3(PMe3)-, adopts an ethane-like geometry with the three chloro ligands on iron and the three methyl groups on phosphorus arranged in a staggered orientation. The reaction of 1 with HO3SCF3 and 2 equiv of PMe3 in diethyl ether produces (η5-2,4-Me2Pd)Fe(PMe3)3 +O3SCF3- (4). In solution, the η5-2,4-Me2Pd ligand in 4 rotates with respect to the Fe(PMe3)3 fragment. Line-shape simulations of the variable-temperature 31P{1H} NMR spectra have enabled us to calculate a ΔG≠ of 11.5 ± 0.5 kcal for this process.
