C 5 H 9 BF3 KS2 ,triclinic, P 1 (no. 2), a =11.9238(5) Å, b =13.6060(5) Å, c =14.0280(3) Å, a =114.995(2)°, b =92.035(2)°, g =92.390(2)°, V =2057.4 Å 3 , Z =8, R gt(F) =0.049, wRref(F 2 ) =0.117, T =296 K.
Source of materialAsolutionof2-methyl-1,3-dithiane (1.34 g, 10 mmol) in 20 mLof dry THFwascooled to -78°Cunder nitrogen. n -BuLi(7.33 mL, 1.5 Min hexane,1mmol) and HMPA(1.8 mL,10mmol) were added dropwise,and the solution wasstirred for 1hatthis temperature. Trimethylborate (1.34 mL,1 .25 g, 12 mmol) wast hen added dropwise at-78°C.The solutionwasstirred at-30°Cfor 1 h. Asaturatedaqueoussolution of potassium hydrogen difluoride (3.12 g, 40 mmol) wasadded at-20°Cto the vigorously stirred solution. The resulting mixture wasallowed to warm to RT for 1h and then stirred for 1h.The solvent wasremoved under reduced pressure, and the resulting white solid wasdried under high vacuum for 2htoremove all water. The solid waswashed with hot acetone. The resulting organic solution wasfiltered, and the solvent wasremoved to afford afluffy white solid. This solid was dissolved in hot acetone and precipitatedwith diethyl ether, after which the solution wascooled to -20°Cto complete precipitation. The product wascollected asawhitecrystalline solid (yield 1.72 g, 72 %).
DiscussionThe title compound crystallizesasdiscrete K + and C 5 H 9 BF 3 S 4 -moieties, of which there are four independentinthe asymmetric unit. Int he structure the K1atom is surrounded by five anions making close contacts with six Fatoms with distances ranging from 2.651(2) Åto 2.914(2) Å,w hile the other three are surrounded by four anions making close contacts with five Fatoms with distances rangingfrom 2.642(2) Åto 2.867(2) Å,2.587(2) Å to 3.067(2)Å,and 2.652(2)Åto 2.835(2) Åfor K2, K3and K4, respectively. The 2-methyl-1,3-dithiano six-membered rings are in different conformations:1isinahalf-chair distortedtowards a chair, 2isinaslightly distorted chair,and 3and 4inchair distorted ones towards ahalf boat. The Cremer and Pople's ringpuckering parameters [1], given in the order 1-4 being: q 2 = 0.43(3) Å,0.0499(4) Å,0.16(3) Å,0.13(4) Å; q 3 =0.685(3) Å,