Multinuclear Magnetic Resonance Spectroscopy of Centered Zirconium Halide Clusters
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abstract
Nuclear magnetic resonance spectra for each of the interstitials within centered [Zr6Z)Cl(i)12Cl(a)(6-n)L(n)]m- clusters (Z = Be, B, C, N, Mn, and Co; L = Cl-, AlCL4-, CH3CN, and/or PPh3; n = 0-6) are reported. For C- and Mn-centered clusters, chemical shifts for both solids and solutions have been measured. Chemical shifts for B-centered clusters were measured in solution. Chemical shifts for Be-, N-, and Co-centered clusters were measured in the solid state. Interstitial carbide resonances for all 10 axially substituted species ({[(ZR6C)Cl12](CH3CN)(n)Cl(6-n)}(n-4), n = 0-6) have been located; their chemical shifts range from 457.7 ppm for {[(Zr6C)Cl12]Cl6}4- to 480.1 ppm for {[(Zr6C)Cl12](CH3CN)6}2+. 11B chemical shifts for boride-centered clusters ({[(Zr6B)Cl12](CH3CN)(n)Cl(6-n)}(n-5), n = 0-5) range from 185 to 193.8 ppm. 11B and 13C data reveal the axially bound chlorides to be substitutionally inert. Chemical shifts for 55Mn-centered clusters range from 5359 ppm (isotropic) for solid RbZr6Cl14Mn to 5618 ppm for [(Zr6Mn)Cl12Cl6]5- in a Cl--rich molten salt. These are the most deshielded manganese compounds presently known. Solid-state 9Be for K3Zr6sCl15Be, 15N for Zr6Cl15N, and 59Co for Zr6Cl15Co reveal chemical shifts of 77.1, 271, and 4082 ppm, respectively (the 9Be data is not corrected for the second-order quadrupolar contribution). A discussion of the origin of large paramagnetic shielding contributions to the chemical shifts of the interstitial atoms is given.
