192373-41-4Relevant academic research and scientific papers
A Bidentate Bisphosphine Functioning in Intramolecular Aliphatic Metalation and as an NMR Spectroscopic Probe for the Metal Coordination Environment
Lesueur, William,Solari, Euro,Floriani, Carlo,Chiesi-Villa, Angiola,Rizzoli, Corrado
, p. 3354 - 3362 (2008/10/09)
The multistep synthesis of the novel diphosphine reference ligand L2, 6, Ph2P(o-C6C6H4C6H 4-o)PPh2, has been streamlined and can be prepared on a ca. 20 g scale. It forms metallacycles with a variety of metal fragments. The resulting, and very rigid, boat-boat conformation forces a proton (Hendo) of the bridging methylene in close proximity to the metal, which in turn renders these protons (Hendo Hexo) diastereotopic. The NMR spectra of [L2MCl2] [M = Pd, 9; M = Pt, 10] and of the organometallic derived compounds [L2Pd(PPh3)], 11, and [L2Pd-(Cl)(η2-CH2Ph)], 12, consist of a pair of doublets, with the Hendo coupled to the P of the metallacycle. The CH2-metal close proximity drives the electrophilic metalation of the bridging methylene by RhCl3 to form [L*2Rh(Cl)2(MeCN)], 13, [L*2 = Ph2P(o-C6H6CHC6-o)PPh2]. A significant example, which shows how the coordination number of the metal can affect the Hexo-Hendo resonance separation, is provided by the couple [L2Ni(C2H4)], 14, and [L2Ni(CO)2], 15. In order to show that the metallacycle size is crucial for the bridging methylene to function as a spectroscopic probe, we complexed the same [Fe(CO)3] fragment to L2, 6, and L'2, 17, [L'2 = Ph2PO(o-C6H2(4,6Bul2)CH2(4,6Bu1 2)C6H2(4,6Bu21)OPPh 2], to give [L'2Fe(CO)3], 19, and [L'2Fe(CO)3], 18. respectively. In complex 17 the diastereotopic nature of these protons and hence the spectroscopic information was lost because of the presence of a 10-membered metallacycle. Crystal data: 9 is triclinic, space group P1?, a = 11.987(1) A?, b= 15.990(2) A?. c = 10.872(1) A?, a = 91.42(1)°, β= 111.01(2)°, γ = 99.86(2)°, V= 1908.2(5) A?3, Z = 2, and R = 0.053; 11 is monoclinic, space group C2/c, a = 39.071(5) A?, b = 13.657(4) A?, c = 19.848(5) A?,β = 92.45(2)°, V= 10581(5) A?3 Z = 8. and R = 0.047; 12 is triclinic, space group P1?, a = 11.289(1) A?, b = 18.769(2) A?, c = 11.077(1) A?, a = 91.20(1)°, β= 111.27(1)°, γ = 105.26(1)°, V = 2107.7(4) A?3, Z = 2, and R = 0.039; 13 is orthorhombic, space group P212121, a = 15.346(2) A?, b = 18.188(3) A?, c = 12.072(2) A?, V = 3369.5(9) A?3, Z = 4. and R = 0.042.
