LANTHANIDE AND YTTRIUM COMPLEXES OF DEPROTONATED 4,13-DIAZA-18-CROWN-6 (DAC) - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF Y[DAC][N(SIME(3))(2)] AND THE NOVEL TRINUCLEAR YTTERBIUM(II) COMPLEX (YB[N(SIME(3))(2)][MU-DAC])2YB

The ability of a deprotonated diazacrown ether, 4,13-diaza-18-crown-6 (DAC), to allow isolation of soluble lanthanide and yttrium complexes was investigated. Reaction of H(2)DAC with Ln[N(SiMe(3))(2)](3) provided soluble complexes, Ln[DAC][N(SiMe(3))(2)] (Ln = Y (1a), Ce (1b)). A single crystal X-ray diffraction study of 1a revealed a seven-coordinate monomer in which the six donors of the DAC Ligand adopt a basketlike conformation around the yttrium atom. [Crystal data: monoclinic space group P2(l)/n, a = 9.471(1) Angstrom, b = 28.786(3) Angstrom, c = 10.567(3) Angstrom, beta = 114.45(1)degrees, V = 2622.5 Angstrom(3), Z = 4, R = 0.010, R(w) = 0.124.] Reaction of H(2)DAC with divalent Yb-[N(SiMe(3))(2)](2)[OEt(2)](2) in 2:3 stoichiometry provided the novel trinuclear cluster {[(Me(3)Si)(2)N]Yb(mu-DAC)}Yb-2 (2). The crystal structure of 2 shows a linear (Me(3)Si)N-Yb-Yb-Yb-N(SiMe(3))(2) arrangement with two DAC amido-N groups bridging between pairs of adjacent Yb centers. The DAC ligand is folded back such that the four ether donors interact with an outer Yb atom (seven-coordinate). The central four-coordinate Yb exhibits distorted tetrahedral coordination. [Crystal data: monoclinic space group P2(l)/n, a = 19.982(3) Angstrom, b = 17.870(2) Angstrom, c = 16.933(3) Angstrom, beta = 113.56(1)degrees, V = 5542 Angstrom(3), Z = 4, R = 0.087, R(w) = 0.104.] Reaction of H(2)DAC with Yb-[N(SiMe(3))(2)](2)[OEt(2)](2) in 1:2 stoichiometry produced the dinuclear complex {Yb[N(SiMe(3))(2)]}(2)(mu-DAC} (3). Divalent Sm[N(SiMe(3))(2)](2)[THF](2) reacts with H(2)DAC to yield trivalent Sm[DAC][N(SiMe(3))(2)] (4) in good yield. Experimental evidence suggests that this product if formed by the unusual Sm(II) reduction of a DAC N-H bond.