Table 3. Experimental Frequencies of the Fundamental Vibrational Modes of CF₃–X (X = I, Br, Cl) in Liquid Argon (89 K) and Shifts Recorded upon Complexation with Different Lewis Bases in Various Cryogenic Solutions^a.

		Δν
	freeb	Me3Nc	Me2Ob	Me2Sd	MeFe	MeCle	EtFe	EtCle
CF3I
ν1	1068.9	+15.1	+11.4	+8.9	+5.5	+3.4	+6.1	+3.1
ν2	741.3	–10.7	–4.1	–6.5	–1.3	–1.3	–2.0	–1.7
ν3	286.4b	–18.1	–2.3b	–12.0	+0.8	–1.0	+0.6	–1.2
ν4	1177.3	–32.9	–18.8	–19.5	–8.8	–7.1	–10.3	–8.2
ν5	539.8			–1.3
ν6	266.2b		+2.2b	–0.2	+2.2		+1.7	+1.2
CF3Br
ν1	1077.1	+5.1	+7.4	+3.8	+4.5		+4.9	+2.8
ν2	759.9	–8.4	–3.0	–3.8	–1.0	–0.8	–0.9	–1.0
ν3	350.2/348.5b	–14.9/–14.4	–1.1/–1.1b	–7.8/–6.0	+1.3/+1.3	–0.1/–0.2	+1.5/+1.4	–0.2/–0.3
ν4	1199.7	–22.2	–13.8	–11.1	–6.6	–4.3	–7.7	–5.2
ν5	546.7		–1.3	–1.2	–0.5	–0.2	–0.5	–0.6
ν6	301.3b		+2.6b	+1.4			+1.8
CF3Cl
ν1	1099.4	+8.1	+7.0
ν2	781.0	–4.5	–1.0
ν3	476.3/468.4	–3.9/–3.9	+2.0/+2.0
ν4	1208.0	–13.8	–10.6
ν5	561.2		–0.8
ν6	348.1

^aAll shifts are calculated from the FTIR and Raman spectra of the free and complexed CF₃–X recorded at the same temperatures. Frequencies and shifts are reported in inverse centimeters.

^bReference (410). Measurements performed in liquid Ar (89 K). For CF₃I and CF₃Br (both free and in complex with DME), ν₃ and ν₆ were obtained in liquid Kr (123 K).

^cReference (409). Measurements performed in different cryosolutions: for CF₃I in liquid Xe (173 K), for CF₃Br in liquid Kr (123 K), for CF₃Cl in liquid Ar (96K).

^dReference (411). Measurements performed in liquid Kr (123 K). For mixed solutions of CF₃Cl and dimethyl sulfide, no features suggesting the formation of a complex were detected. This is not surprising when considering that the complexes of the same Lewis acid with dimethyl ether and trimethylamine could be observed only at the lower temperatures provided by the use of liquid Ar.

^eReference (412). Measurements performed in liquid Kr (123 K).