Rotational spectroscopy of H3P center dot center dot center dot BrCl and the systematics of intermolecular electron transfer in the series B center dot center dot center dot BrCl, where B=CO, HCN, H2O, C2H2, C2H4, H2S, NH3, and PH3
Ac. Legon et al., Rotational spectroscopy of H3P center dot center dot center dot BrCl and the systematics of intermolecular electron transfer in the series B center dot center dot center dot BrCl, where B=CO, HCN, H2O, C2H2, C2H4, H2S, NH3, and PH3, J CHEM PHYS, 113(13), 2000, pp. 5278-5286
Ground-state rotational spectra of the isotopomers H3P ...(BrCl)-Br-79-Cl-3
5, H3P ...(BrCl)-Br-81-Cl-35, H3P ...(BrCl)-Br-79-Cl-37, H3P ...(BrCl)-Br-8
1-Cl-37, D3P ...(BrCl)-Br-79-Cl-35, and D3P ...(BrCl)-Br-81-Cl-35, of the p
hosphine-bromine monochloride complex were observed by the pulsed-jet, Four
ier-transform method, incorporating a mixing nozzle to preclude reaction am
ong the component gases. Each isotopomer exhibited a symmetric-top-type spe
ctrum which yielded accurate values of the spectroscopic constants B-0, D-J
, D-JK, chi(aa) (Br), chi(aa) (Cl), M-aa (Br), and M-bb (Br) on analysis. I
nterpretations of the changes in the B-0 values with isotopomer showed that
the intermolecular bond involves P and Br, with r(P ... Br)=2.869(1) Angst
rom and that the BrCl bond increases in length by similar to 0.04 Angstrom
on complex formation. Changes in the halogen nuclear quadrupole coupling co
nstants when H3P ... BrCl is formed lead, with the aid of the Townes-Dailey
model, to the conclusion that a fraction delta(i)=0.100(5) of an electron
is transferred from P to Br on complex formation, while the polarization of
BrCl by PH3 can be viewed as the transfer of 0.128(2)e from Br to Cl, lead
ing to a net change of -0.028(5)e in the population of the 4p(z) orbital of
Br. The complex is only of moderate strength, with an intermolecular stret
ching force constant k(sigma)=11.5 Nm(-1). Values of delta(i), similarly de
termined, for the series B ... BrCl, where B=CO, HCN, H2O, C2H2, C2H4, H2S,
NH3, or PH3, are presented. It is shown that the variation of delta(i) wit
h the ionization energy I-B of the Lewis base B can be described by an expr
ession delta(i)=A exp(-bI(B)). This behavior is compared with that for the
corresponding series B ... ICl. (C) 2000 American Institute of Physics. [S0
021-9606(00)01037-0].