Journal of the American Chemical Society, Vol.119, No.40, 9449-9459, 1997
Multinuclear magnetic resonance spectroscopy of centered zirconium halide clusters
Nuclear magnetic resonance spectra for each of the interstitials within centered [(Zr(6)Z)(Cl12Cl6-nLn)-Cl-i-L-a](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)Cl-12](CH3CN)(n)Cl6-n}(n-4), n = 0-6) have been located; their chemical shifts range from 457.7 ppm for {[(Zr6C)Cl-12]Cl-6}(4-) to 480.1 ppm for {[(Zr6C)Cl-12](CH3CN)(6)}(2+). B-11 chemical shifts for boride-centered clusters ({[(Zr6B)Cl-12](CH3CN)(n)Cl6-n}(n-5), n = 0-5) range from 185 to 193.8 ppm. B-11 and C-13 data reveal the axially bound chlorides to be substitutionally inert. Chemical shifts for Mn-55-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 Be-9 for K3Zr6Cl15Be, N-15 for Zr6Cl15N, and Co-59 for Zr6Cl15Co reveal chemical shifts of 77.1, 271, and 4082 ppm, respectively (the Be-9 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.