syn-Sesquinorbornenyl carbocations and their boron analogues: an ab initio and DFT study

X-ray structural analyses and DFT study of 7-thianorbornenes: 4-aza-4-phenyl-10-thiatricyclo[5.2.1.0.2,6]deca-8-ene-3,5-dione and 4-aza-l,4,7-trimethyl-10-thiatricyclo[5.2.1.0.2,6]deca-8-ene-3,5-dione

“…9053 (2) 7738 (2) 7292 (1) 19 (1) C(4) 7608 (2) 7916 (2) 6818 (1) 18(1) C (5) 6406 (2) 7208 (2) 7432 (1) 16(1) C (6) 6771 (2) 5481 (2) 7777 (1) 16(1) C (7) 6435 (2) 8390 (2) 8212 (1) 15(1) C (8) 6831 (2) 7265 (2) 8956 (1) 14(1) C (9) 7356 (2) 4215 (2) 9190 (1) 15(1) C (10) 8821 (2) 3866 (2) 9340 (1) 17(1) C (11) 9186 (2) 2493 (2) 9846 (1) 19(1) C (12) 8090 (2) 1491 (2) 10191 (1) 19(1) C (13) 6628 (2) 1863 (2) 10037 (1) 18(1) C (14) 6249 (2) 3233 (2) 9537 (1) 17 (1) N(1) 6965 (1) 5621 (2) 8657 (1) 15 (1) O(1) 6903 …”

“…Particularly interesting in this context are molecules in which the carbon atom of the methano-bridge is replaced by a heteroatom [2]. So far, experimental and highlevel computational studies dealing with hetero-norbornene counterparts with oxygen [3][4][5], boron [6], phosphorus [7], silicon and germanium [8] bridges were reported. There is also a low-level computational study (MINDO/3) by Gleiter dealing with deviation of the double bond from planarity in dithiasesquinorbornene [9].…”

Ab initio MO and DFT study of syn-sesquinorbornatrienyl dication and its isoelectronic boron analogueElectronic supplementary information (ESI) available: bond distances and bond angles of structures 6a, 6c, 7a and 7c calculated at the MP2/6-31+G* and B3LYP/6-31G* levels of theory (Table S1). See http://www.rsc.org/suppdata/nj/b4/b403802a/

“…Geometry of structure 3c is very similar to that of syn-7,7 0 -sesquinorbornenyl dication (1) with the þ CH groups tilted toward the central double bond bridge. 6 It is interesting to note that the tilting angles a (in 3c) are smaller by 3.6 than in dication 1. 6 This is in accordance with the trend observed previously on comparing 7-norbornenyl with 7-norbornadienyl cation (8) (81.4 vs. 78.4 ).…”

“…6 It is interesting to note that the tilting angles a (in 3c) are smaller by 3.6 than in dication 1. 6 This is in accordance with the trend observed previously on comparing 7-norbornenyl with 7-norbornadienyl cation (8) (81.4 vs. 78.4 ). It is also interesting to note that the degree of pyramidalisation of the C(1) and C(2) atoms of 3c as measured by the out of plane angle f, is lower than that of 1 (17.9 vs. 14.9 at the MP2 level).…”

“…In a recently reported paper we have discussed the nature of homoaromatic interaction in 1 and 2 obtained by fusing two 7-norbornenyl rings and their isoelectronic boron analogue into syn-sesquinorbornenyl framework. 6 It was shown that both species exhibit 4-center-2-electron (4c/2e) bonding instead of the 3-carbon-2-electron (3c/2e) bonding present in their isolated bicyclic subunits. [2][3][4][5] This in turn has led to a dramatic change in pyramidalisation of the olefinic carbon atoms and consequently to the change of the characteristic hinge-like bending 7,8 (i.e.…”