Table 1. DFT-calculated pK _a values and Gibbs energies ΔG _rel of deprotonation of R–CH₂–boryl and other compounds with the cyclopentadienyl anion Cp^–

Entry	X–H	pK a			ΔG rel (298 K) a [kcal mol–1]
		Vacuum	CH2Cl2	DMSO	Vacuum	CH2Cl2	DMSO
1	C5H9–H	61.1	60.7	60.4 (exp: 58) b	+58.7	+58.2	+57.7
2	PhCH2–H	37.4	41.1	41.7 (exp: 41) c	+26.4	+31.5	+32.2
3	9-BBN–CH2–H	26.7	32.4	33.1	+11.9	+19.6	+20.5
4	Mes2B–CH2–H	16.6	27.8	29.2	–1.9	+13.3	+11.2
5	(C6F5)2B–CH2–H	1.8	16.2	18.3	–22.0	–2.4	+0.5
6	C5H5–H(Cp–H)	18.0 d	18.0 d	18.0 d	0.0	0.0	0.0
7	(C6F5)2B–C(CH3)2–H	–2.9	13.0	15.4	–28.4	–6.8	–3.6
8	(C6F5)2B–CH(Ph)–H	–6.8	9.3	11.6	–33.8	–11.9	–8.7
9	(C6F5)2B–CH(CH CH2)–H	–8.6	6.7	9.0	–36.3	–15.4	–11.3
10	Mes2EtP+–H	–61.1	–2.5	7.0	–106.6	–27.9	–15.0

^aCalculated Gibbs energy ΔG _rel (TPSS-D3/def2-TZVP + COSMO) of the reaction X–H + Cp^– → Cp–H + X^–.

^bExtrapolated, see ref. 10.

^c Ref. 11a.

^dExperimental pK _a of Cp–H in DMSO (ref. 10), taken here as the point of reference.