Atom Transfer as a Preparative Tool in Coordination Chemistry. Synthesis and Characterization of Cr(V) Nitrido Complexes of Bidentate Ligands

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Abstract
The transfer of a terminal nitrido ligand from MnV(N)(salen) to Cr(III) complexes is explored as a new preparative route to CrV nitrido complexes. Reaction of MnV(N)(salen) with labile CrCl3(THF)3 in acetonitrile solution precipitates [Mn(Cl)(salen)]·(CH3CN) and yields a solution containing a mixture of CrV nitrido species with only labile auxiliary ligands. From this solution CrV nitrido complexes with bidentate monoanionic ligands can be obtained in high yields. Five coordinate complexes of 8-hydroxoquinolinate (quin), 1,3-diphenylpropane-1,3-dionate (dbm), and pyrrolidinedithiocarbamate (pyr-dtc) have been structurally characterized: Cr(N)(quin)2 (1) crystallizes as compact orange prisms in the triclinic space group P1̄ with cell parameters a = 7.2450(6) Å, b = 8.1710(4) Å, c = 13.1610(12) Å, α = 80.519(6)°, β = 75.721(7)°, γ = 75.131(5)°, V = 725.47(10) Å3, Z = 2. Cr(N)(dbm)2 (2) crystallizes as green rhombs in the orthorhombic space group Pbca with cell parameters a = 14.6940(6) Å, b = 16.4570(18) Å, c = 19.890(3) Å, V = 4809.8(8) Å3, Z = 8. Cr(N)(pyr-dtc)2 (3) crystallizes as orange prisms in the monoclinic space group P21/c with cell parameters a = 14.8592(14) Å, b = 8.5575(5) Å, c = 11.8267(12) Å, β = 106.528(7)°, V = 1441.7(2) Å3, Z = 4. Complexes 2 and 3 represent new coordination environments for first row transition metal nitrido complexes. The d-orbital energy splitting in these systems with relatively weak equatorial donors differs significantly from the pattern in vanadyl and the previously known first row transition metal nitrido complexes. The dx2-y2 orbital in 2 and 3 is lower in energy and well resolved from the M−N π* orbitals {dzx,dyz}.