Abstract: The title compoud and its related derivatives show a certain degree of thermal lability and were reported as effective carbon-carbon type initiators for the polymerzation of styrene and other monomers.The crystal and molecular structrues of two isimers of the title compoud has been determined.
1, meso-(I), C_(22)H_(18)N_4O_8 space group, p1, a=0.7860(3), b=0.8350(2), c=0.9303(3) nm, a=89.29(2), β=65.49(2), γ=83.27(2), Z=1, V=0.5512 nm, μ(MoKα)=1.02 cm~(-1), D_c=1.405 mg m~(-3), final R=0.064 for 1729 observed reflections.
2, racemic-(I), C_(22)H_(18)O_8·C_6H_6, space group C2/C, a=1.8395(5), b=1.102(2), c=1.3865(4) nm, β=92.16(2)°, Z=4, V=2.809(1) nm, μ(MoKα)=0.89 cm~(-1), D_c=1.458 mg m~(-3), final R=0.084 for 2202 observed reflections.
There are numerous intramolecular non-bonded atomic eontacts shorter than the expected van der Waals distances. The strong steric interactions of these atomic pairs lead to enormous strain within the molecule and thus to anomalous bond lengths and angles as well as thermal instability The stretching of the centra C—C bonds, 0.1601(4) nm for meso-(I), 0.1587(6) nm for racemic-(I), is particularly remarkable. It was shown the “steric acceleration” plays an important role during the cleavage of the central C—C bonds.