The influence of substituents on the geometry of the cyclopropane ring. VII The molecular and crystal structures of bicyclopropylidene (C3H4C3H4) and (dicyclopropylmethylene)cyclopropane [(C3H5)2CC3H4]†

Crystals of bicyclopropylidene grown from the liquid are monoclinic, space group P21/n, a = 4.9744(3), b = 12.4870(8); c = 4.0366(3) A, β = 95.077(7)° (173 K), Z = 2. The final R for 450 independent observed reflections is 0.036. Crystals of (dicyclopropylmethylene)cyclopropane grown from the liquid are monoclinic, space group P21/a. a = 16.781(2), b = 7.260(1), c = 13.665(1) A, β = 99.28(1)° (123 K), Z = 8. The final R for 2592 independent observed reflections is 0.046. The dimensions of the cyclopropylidene moiety in the molecules of both compounds are very similar. The (average) lengths of the distal bonds are 1.549 and 1.547 A, respectively, and the (average) length of the vicinal bonds is 1.472 A in both molecules. The average dimensions of the cyclopropane rings in the molecules of the second compound are 1.505 A for the distal and 1.513 A for the vicinal bonds. There is a significant difference between the lengths of the double bonds in the two compounds [1.307(2) and 1.327(2) A, respectively; all distances corrected for librational motion of the molecules].