Element-element bonds .8. Synthesis, molecular and crystal structure of dibromo(2,4,6-trimethylphenyl)bismuthane

Dichloro- (1) und dibromo(2,4,6-trimethylphenyl)bismuthane (2) are obtained in relatively high yields from metathesis reactions of the corresponding bismuth(III) halides with tris(2,4,6-trimethylphenyl)bismuthane. An X-ray structure determination of the dibromo derivative 2 (monoclinic, P2(1)/c; a=896.2(2); b=1531.9(3); c=1713.3(3)pm; beta=94.31(3)degrees at -100+/-3 degrees C; Z=8 molecules; R=0.059) shows two crystallographically independent molecules to build up a zigzag chain via strong Bi-Br .. Bi bridges (Bi-Br 282 and 281; Br .. Bi 302 and 302 pm) and relatively weak eta(6)-arene .. Bi interactions (mean values Bi .. C 348 and 359 pm); for sterical reasons one bromo substituent of each molecule is not involved in coordinative bonding (Bi-Br 262 and 261 pm). To allow a better comparison of Bi-C-ipso bond lengths and arene .. Bi contacts, relevant values of a greater number of related compounds have been compiled; for some of these examples arene Bi interactions had not been reported before. Ir and Raman bands below 350 cm(-1) are assigned to stretching frequencies of the BiCl2 (1) and BiBr2 (2) fragments, respectively.