Table 3. Effect of solvent and LAs on the rate of CO₂ insertion into 2.

Entry	Solvent	k 1 (M–1 s–1) at 273 K	Rate increase	Activation parameters a
1a	THF	1.8 (2) × 103	—	ΔH‡ = 4.4 (3)
				ΔS‡ = –28 (1)
				ΔG‡298 K = 12.6 (4)
1b b	THF + LiPF6	1.9 (2) × 103	—	—
1c b	THF + NaBArF4	1.9 (2) × 103	—	—
2	Benzene	3.7 (4) × 103	2	ΔH‡ = 3.0 (3)
				ΔS‡ = –31 (1)
				ΔG‡298 K = 12.3 (3)
3	Pyridine	7.9 (8) × 103	4	ΔH‡ = 4.7 (4)
				ΔS‡ = –23 (3)
				ΔG‡298 K = 11.6 (3)

^aΔH^‡ and ΔG^‡ in kcal mol^–1 and ΔS^‡ in cal mol^–1 K^–1.

^b[LA] = 6.0 mM (20 equivalents with respect to 2).