Dibenzo[b,e]-7,7,8,8-tetraneopentyl- and dibenzo[b,e]-7,7,8,8-tetraisopropyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes: Interaction with tetracyanoethylene and transition metal chlorides

Article abstract of DOI:10.1016/0022-328X(95)05907-7

Dibenzo[b,e]-7,7,8,8-tetraalkyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes (1: R = ^tBuCH₂; 2: R = ⁱPr) were prepared by the reaction of ClR₂SiSiR₂Cl with lithium anthracenide in 1,2-dimethoxyethane (DME) at room temperature. The structure of 1 was determined by X-ray crystallography. Crystal data for 1: monoclinic, C2/c, a = 12.941(2), b = 14.601(1), c = 35.109(6) A, β = 94.957(7)°, V = 6609(2) A³, Z = 8, R = 0.048, R_w = 0.053 for 4037 reflections. Compounds 1 and 2 show the bathochromic shift of ¹L_a and ¹L_b bands in UV spectra and exhibit considerably low oxidation potentials due to effective σ-π conjugation. Compounds 1 and 2 form charge-transfer complexes with tetracyanoethylene (TCNE). In the case of 1, the charge-transfer complex (1: TCNE = 2:1) could be isolated as crystals and the structure was determined by X-ray crystallography. Crystal data for the 1-TCNE complex: monoclinic, C2/c, a = 10.267(2), b = 36.077(4), c = 20.022(4) A, β = 100.680(8)°, V = 7288(2) A³, Z = 4, R = 0.045, R_w - 0.077 for 4120 reflections. The action of transition metal chlorides on 2 resulted in [4 + 2] cycloreversion to form ClⁱPr₂SiSiⁱPr₂Cl and anthracene.