Matrix isolation studies of reactive intermediate complexes

Prereactive Complexes of Dihalogens XY with Lewis Bases B in the Gas Phase: A Systematic Case for the Halogen Analogue B⋅⋅⋅XY of the Hydrogen Bond B⋅⋅⋅HX

“…In general the B´´´HX interactions are of the weak electrostatic type, [67,68] and the k s values of a large number of complexes can be reproduced by the empirical Equation (10) [61,62] where k s cN B E HX (10) N B and E HX are gas-phase nucleophilicities and electrophilicities assigned to the individual molecules B and HX, respectively, and c is a constant. Values of N B and E HX for a range of B and HX are given in Table 4 and, with the value [32] (3.6) 5.1 [40] (6.3) 6.3 [45] (6.3) 7.0 [53] (6.9) C 2 H 2 ± (2.0) 5.6 [36] (5.4) ± (7.8) 9.4 [47] (9.5) 10.0 [54] [27] (6.0) ± (8.7) 10.5 [46] (10.6) 11.0 [55] (11.5) HCN 2.6 [63] (2.3) 6.6 [37] (6.2) ± (9.1) 11.1 [49] (11.0) 12.3 [56] (12.0) H 2 S 2.4 [64] (2.6) 6.3 [35] (6.9) ± (10.0) 12.2 [48] (11.0) 13.3 [57] (13.2) NH 3 4.7 [65] (4.7) 12.7 [38] (12.6) 18.5 [39] [a] Values in parentheses are calculated from the N B and E XY values of Table 5 by using Equation (10). See text for discussion of the discrepancy of observed and calculated k s for H 3 N´´´ClF.…”

“…We choose arbitrarily that E BrCl 9.0 and then use k s for the B´´´BrCl series [45±49] in Equation (10) to obtain the N B values for CO, C 2 H 2 , C 2 H 4 , HCN, and H 2 S shown in Table 5. We do not use the H 3 N´´´BrCl value [50] to obtain N NH 3 because the approximation of weak interaction probably does not hold in this complex, which has k s 26.7(3) N m À1 .…”

“…We do not use the H 3 N´´´BrCl value [50] to obtain N NH 3 because the approximation of weak interaction probably does not hold in this complex, which has k s 26.7(3) N m À1 . Instead, we employ k s 12.7 N m À1 of H 3 N´´´Cl 2 [38] with E Cl 2 5.1 (see below) to obtain N NH 3 9.9 from Equation (10). The choices of E F 2 1.9, E Cl 2 5.1, E Br 2 7.4, E BrCl 9.0, and E ClF 9.8 together with the N B values of Table 5 then reproduce the observed k s values (see Table 3) reasonably well; exceptions are for H 3 Ń´´B rCl and H 3 N´´´ClF, which have observed k s values considerably larger than those predicted on the basis of the E XY and N B values of Table 5 by using Equation (10).…”

“…Instead, we employ k s 12.7 N m À1 of H 3 N´´´Cl 2 [38] with E Cl 2 5.1 (see below) to obtain N NH 3 9.9 from Equation (10). The choices of E F 2 1.9, E Cl 2 5.1, E Br 2 7.4, E BrCl 9.0, and E ClF 9.8 together with the N B values of Table 5 then reproduce the observed k s values (see Table 3) reasonably well; exceptions are for H 3 Ń´´B rCl and H 3 N´´´ClF, which have observed k s values considerably larger than those predicted on the basis of the E XY and N B values of Table 5 by using Equation (10). These larger values are thought to arise from a nonneglible charge transfer, as represented by a small contribution of the ionic structure [H 3 NX] ´´´YÀ to the valence bond description of these complexes.…”

Complexes of Formaldehyde and α-Dicarbonyls with Hydroxylamine: FTIR Matrix Isolation and Theoretical Study

“…Many reactions begin with the formation of the molecular complexes between the substrates, which also can be isolated in the matrices. Using the FTIR spectroscopy and ab initio methods, we are able to distinguish the nature of interactions and the structures of the isolated complexes [ 2 , 3 ].…”