TY - JOUR
T1 - A homologous series of base-free organo(alkaline-earth) metallocenes
T2 - Synthesis and molecular structures of [1,2,4-(SiMe3) 3C5H2]2(Ca, Sr, Ba)
AU - Harvey, Melanie J.
AU - Quisenberry, Keith T.
AU - Hanusa, Timothy P.
AU - Young, Victor G.
PY - 2003/9/26
Y1 - 2003/9/26
N2 - Bis[1,2,4-tris(trimethylsilyl)cyclopentadienyl] complexes [1,2,4-(SiMe 3)3C5H2]2Ae [(Cp 3Si)2Ae; Ae = Ca (1), Sr (2), Ba (3)] are isolated from the 2:1 reaction of K[Cp3Si] and AeI2 in diethyl ether. Under the same reaction conditions used for the heavier metallocenes the corresponding (Cp3Si)2Be compound was not formed, although calculations suggest that the beryllocene would be sterically feasible. Compound 1 crystallizes as a bent monomer from hexanes (ring centroid-Ca-ring centroid = 166.7°) with two η5-Cp3Si ligands on the calcium atom [Ca-C(av) = 2.63(2) Å]. Metallocene 2, the first crystallographically characterized example of an unsolvated strontocene, is also isolated as a bent monomer (159.4°) from hexanes with two η 5-Cp3Si ligands on the strontium atom [Sr-C(av) = 2.819(2) Å]. Compound 3 crystallizes on sublimation as a coordination dimer in which each barium atom is flanked by two η5-Cp3Si rings [Ba-C(av) = 3.01(2) Å] and one methyl group from a neighboring Cp′ ring; the intermolecular Ba⋯C(methyl)′ distance is 3.275(6) Å. The amount of bending observed in 1-3 and other Group-2 metallocenes varies with the metals, the steric bulk of the cyclopentadienyl ligands, and crystal packing effects, and is not easily predictable. (
AB - Bis[1,2,4-tris(trimethylsilyl)cyclopentadienyl] complexes [1,2,4-(SiMe 3)3C5H2]2Ae [(Cp 3Si)2Ae; Ae = Ca (1), Sr (2), Ba (3)] are isolated from the 2:1 reaction of K[Cp3Si] and AeI2 in diethyl ether. Under the same reaction conditions used for the heavier metallocenes the corresponding (Cp3Si)2Be compound was not formed, although calculations suggest that the beryllocene would be sterically feasible. Compound 1 crystallizes as a bent monomer from hexanes (ring centroid-Ca-ring centroid = 166.7°) with two η5-Cp3Si ligands on the calcium atom [Ca-C(av) = 2.63(2) Å]. Metallocene 2, the first crystallographically characterized example of an unsolvated strontocene, is also isolated as a bent monomer (159.4°) from hexanes with two η 5-Cp3Si ligands on the strontium atom [Sr-C(av) = 2.819(2) Å]. Compound 3 crystallizes on sublimation as a coordination dimer in which each barium atom is flanked by two η5-Cp3Si rings [Ba-C(av) = 3.01(2) Å] and one methyl group from a neighboring Cp′ ring; the intermolecular Ba⋯C(methyl)′ distance is 3.275(6) Å. The amount of bending observed in 1-3 and other Group-2 metallocenes varies with the metals, the steric bulk of the cyclopentadienyl ligands, and crystal packing effects, and is not easily predictable. (
KW - Alkaline-earth metals
KW - Metallocenes
KW - Solid-state structures
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U2 - 10.1002/ejic.200300284
DO - 10.1002/ejic.200300284
M3 - Article
AN - SCOPUS:0141558999
SN - 1434-1948
SP - 3383
EP - 3390
JO - European Journal of Inorganic Chemistry
JF - European Journal of Inorganic Chemistry
IS - 18
ER -