87711-99-7Relevant articles and documents
Synthesis and characterization of homoleptic complexes of the chelating bidentate isocyano ligand t-BuDiNC
Plummer, Daniel T.,Angelici, Robert J.
, p. 4063 - 4070 (2008/10/08)
The six-coordinate homoleptic complexes [M(t-BuDiNC)3](PF6)z (M = Cr, z = 0, 1, 2; M = Mn, z = 1, 2; M - Fe, z = 2; M = Co z = 3) (t-BuDiNC = 1,2-bis(4-tert-butyl-2-isocyanophenoxy)ethane) have been prepared. The Co(III) complex of this series represents the first example of a hexakis(isocyanide) derivative of trivalent cobalt. Infrared spectra of the complexes show v(C≡N) to increase with increasing charge on the complex or, for complexes of the same charge, with increasing atomic number. A comparison of the integrated intensities of the infrared (vC≡N) bands of the 18-electron d6 members of this series (M = Cr(0), Mn(I), Fe(II), Co(III)) shows the band intensity to decrease in a near-linear fashion in the order Cr(0) > Mn(I) > Fe(II). This trend is interpreted to indicate decreasing dπ-π* CN back-bonding from the metal to the ligands in the same order. The very low intensity of the v(C≡N) band of the Co(III) complex suggests that such back-bonding is of little or no importance in this case. Cyclic voltammetric studies show quasi-reversible interconversions among the species [Cr(t-BuDiNC)3]z+ (z = 0, 1, 2, 3) and [Mn(t-BuDiNC)3]z+ (z = 1, 2, 3); they also indicate a slight thermodynamic destabilization of the trivalent complexes relative to analogues containing para-substituted phenyl isocyanides or phenyl isocyanide itself. Electronic spectra of these homoleptic six-coordinate complexes are interpreted as arising from dπ → π* CN transitions; their energies are affected by both charge and atomic number. Syntheses of the pseudotetrahedral complexes Ni(CO)2(t-BuDiNC), Ni(t-BuDiNC)2, and [Cu(t-BuDiNC)2]BF4 are also reported. The existence of these complexes as mononuclear species (verified for Ni(CO)2(t-BuDiNC) by vapor-pressure osmometry) demonstrates that the t-BuDiNC ligand is capable of chelating to a metal center in which the preferred C-M-C angles are considerably greater than 90°.
