SYNTHESIS AND X-RAY CRYSTAL-STRUCTURES OF ALKALINE-EARTH METALLOCENESWITH PENDANT SUBSTITUENTS

Deprotonation of [(2-C5H4N)CH(2)CMe(2)]C5H5 (= HCp(py)) and CH3OCH2CH2 C5H5 (= HCp(xi)) with Ae[N(SiMe(3))(2)](2) (Ae = Ca, Sr, Ba) in toluen e produces the corresponding metallocenes, Cp'(2)Ae, in high yield. H- 1 NMR data reveal that the calcium complex (Cp(py))(2)Ca does not bind tetrahydrofuran. The solid state structures of (Cp(py))(2)Sr and (Cp( xi))(2)Ca were obtained by single crystal X-ray analysis, and found to be monomeric, with the Lewis base substituents on the cyclopentadieny l rings coordinated to the metal centers. Crystals of (Cp(py))(2)Sr gr own from toluene are orthorhombic, space group Pbcn, with a = 11.988(4 ) Angstrom, b = 16.141(4) Angstrom, c = 12.572(4) Angstrom, V = 2433(1 ) Angstrom(3), Z = 4, R = 0.038, R(w) = 0.043 based on 635 observed re flections. The complex possesses a bent metallocene geometry and conta ins a crystallographically imposed two-fold rotation axis passing thro ugh the strontium. The average Sr-C and Sr-N distances are 2.85(1) and 2.660(7) Angstrom respectively, and the ring centroid-Sr-ring centroi d angle is 141.1 degrees. Crystals of (Cps),Ca grown from toluene are monoclinic, space group P2(1)/n, with a = 6.912(4) Angstrom, b = 15.11 4(2) Angstrom, c = 15.435(3), beta = 100.34(2)degrees, V = 1586.3(9) A ngstrom(3), Z = 4, R = 0.041, R(w) = 0.048 based on 1318 observed refl ections. The complex also has a bent metallocene geometry, with averag e Ca-C and Ca-O distances are 2.670(6) and 2.407(3) Angstrom respectiv ely; the ring centroid-Ca-ring centroid angle is 136.6 degrees.