Gas-solid structure differences in the donor-acceptor complex (CH3)2HN-SO2

The crystal structure of the donor — acceptor adduct (CH3)2HN−SO2 is reported. Crystals of the compound are clear prisms, space group Pna21; at −96°C,a=9.894(1),b=6.051(2),c=16.478(3) A,D=1.469 g/cm3,V=786.6(5) A,Z=8. The unit cell contains two crystallographically independent adducts, with N−S bond lengths of 2.015(3) A and 1.991(3) A. The average value, 2.00(1) A is 0.33(4) A shorter than the 2.34(3) A value previously determined from microwave spectroscopy of the gas phase species, revealing a large medium effect on the length of the donor — acceptor bond. The structural results are compared with published data for the trimethylamine — SO2 adduct, and discussed in terms of existing experimental and theoretical results for other donor — acceptor systems.