34390-31-3Relevant academic research and scientific papers
Preparation and Properties of tetrahedro-Tetraphosphorus Complexes of Rhodium and Iridium. Molecular and Electronic Structure of 2-P4)(PPh3)2>
Ginsberg, Alvin P.,Lindsell, W. Edward,McCullough, Kevin J.,Sprinkle, Charles R.,Welch, Alan J.
, p. 403 - 416 (1986)
White phosphorus dissolved in dichloromethane or diethyl ether at -78 deg C reacts with the Rh(I) or Ir(I) complexes (M = Rh, X = Cl, Br, I, L = PPh3; M = Rh, X = Cl, L = P(p-tol)3, P(m-tol)3, AsPh3; M = Ir, X = Cl, L = PPh3) to form yellow or orange tetrahedro-tetraphosphorus complexes . 31P NMR spectroscopy of in CD2Cl2 at low temperatures shows the P4 ligand to be η2-coordinated and deshielded by ca. 240 ppm relative to free P4.The P4 units act as A2B2 spin systems coupling to two 31P nuclei of PPh3 ligands (X2) and to 103Rh (I = 0.5) to give an overall A2B2MX2 spin system.The vibrational frequencies of the P4 molecule in the rhodium complexes have been identified by infrared and Raman spectroscopy and are found to be from 15 to 90 cm-1 lower in energy than the corresponding frequencies in free P4.An X-ray structure determination on *2CH2Cl2 at 185 K shows the crystals to be triclinic, space group P1, with a = 11.853(2) Angstroem, b = 12.568(8) Angstroem, c = 14.505(2) Angstroem, α = 104.41(4) degree, β = 103.42(13) degree, γ = 84.22(4) degree, V = 2033.5(19) Angstroem3, D0 = 1.58 g cm-3, Z = 2, and Dc = 1.562 g cm-3.The P4 molecule is η2-bonded to the rhodium atom (mean Rh-P = 2.293 Angstroem) with the metal-bonded P-P edge standing perpendicular to the remaining coordination plane of the metal.The phosphine ligands are bent away from the tetraphosphorus group toward the chlorine ( support the analogy between η2-bonded P4 and η2-bonded alkene or S2; the "back-bonding" component may be traced to a three-orbital-four-electron interaction between P4 and the RhCl(PH3)2 fragment.Xα calculations show that the most important contribution to the Rh-P4 covalent bond comes from an equatorial in-plane ? overlap of Rh4dyz with a P4 2P?* orbital.There is also a contribution from ? overlap of an Rh(4dz2, 4dx2-y2, 5s) hybrid orbital with a P4 2P(p?, ?, s?) hybrid.The calculated P-P bond order is 0.4 for the bonded edge and 1.0 for the opposite tetrahedral edge of the P4 ligand.In an EPA glass at liquid nitrogen temperature (X = Cl, Br) shows five absorptions in the 700-260-nm region.These are assigned to one-electron transitions, with good agreement between the obdserved and calculated energies.The absorptions owe most of their intensity to metal -> P4 and metal -> phosphine charge transfer.
