Molecular Structure of a Benzocyclobutadiene

Abstract

solvent is then removed under vacuum and the residue taken up in benzene, filtered and crystallized from pentane/toluene. 0.68g ZnC12 affords 2.7g (69%) (3a) [m.p. 77"C], while 0.92g CdC12 affords 2.848 (65%) ( 3 b ) [m.p. 94"C], and 1.41 g (Me3P)2NiC12 affords 3.0g (78 %) ( 3 c ) [m.p. 90°C

Structure of 3,4-bis(trimethylsilyl)bicyclo[4.2.0]octa-1,3,5-triene

“…1. Positional parameters as well as bond lengths and angles are listed in Tables 1 and 2 The molecular geometry of this compound is consistent with those of other bicyclo [4.2.0] octa-1,3,5trienes (Mak & Trotter, 1964;MacDonald, Lawrence & Cava, 1965;Hardgrove, Templeton & Templeton, 1968;Lawrence & MacDonald, 1969;Allen & Trotter, 1970a,b;Crawford & Marsh, 1973;Thummel, Korp, Bernal, Harlow & Soulen, 1977;Webber, Petcher & Loosli, 1977;Winter & Straub, 1978;Hart, Jeffares, Teuerstein & Ward, 1978;Thummel & Nutakul, 1978;Straub, D6ring & Winter, 1979;Korp & Bernal 1979;Ward, 1980;Hart, Teuerstein, Jeffares, Kung & Ward, 1980). The average Si-C(methyl) bond lengths are in agreement with recently published values (Hursthouse & Malik, 1979).…”

Norcorrole: Aromaticity and Antiaromaticity in Contest

“…Aromaticity and antiaromaticity, two essential concepts deeply ingrained in chemical thinking, are usually associated with Hückel's familiar 4n + 2 and 4n rules. Having both aromatic and antiaromatic behavior within the same molecule is uncommon; examples are limited to fused rings with 4n + 2 and 4n π electrons such as benzocyclobutadiene [1][2][3][4][5] and biphenylene. 3,4,6,7 As a rule, fused 4n + 2 and 4n rings both distort, leading to significant decreases of aromatic and antiaromatic character.…”

“…Aromaticity and antiaromaticity, two essential concepts deeply ingrained in chemical thinking, are usually associated with Hückel’s familiar 4 n + 2 and 4 n rules. Having both aromatic and antiaromatic behavior within the same molecule is uncommon; examples are limited to fused rings with 4 n + 2 and 4 n π electrons such as benzocyclobutadiene − and biphenylene. ,,, As a rule, fused 4 n + 2 and 4 n rings both distort, leading to significant decreases of aromatic and antiaromatic character. The analysis of the isotropic magnetic shielding , enveloping Ni II norcorrole (NiNc) and norcorrole (H 2 Nc) shows that these molecules provide unusual examples of conjugated systems with high antagonistic levels of antiaromaticity and aromaticity.…”

Manifestations of Antiaromaticity in Organic Materials: Case Studies of Cyclobutadiene, Borole, and Pentalene

“…NMR shifts of δ 6.26 and 5.78 were attributed to the benzene ring and δ6.36 to the olefin moiety. [32] Combined with crystallographic data, [33] the researchers suggested that 22 is nonaromatic and is better represented by 22 a (Scheme 5c).…”