Table 1.

Experimental and calculated spectroscopic and structural data of [Fe(CO)₅ oDFB]^.+[Al(OR^F)₄]⁻, 1 and 2. All calculations were done at the BP86‐(D3BJ)/def2‐TZVPP level of theory.

	IR[a] solid $\tilde{\nu }$ (CO) [cm−1]	IR[a] solution $\tilde{\nu }$ (CO) [cm−1]	IR calc. (C 4v) $\tilde{\nu }$ (CO) [cm−1]	IR[b] calc. $\tilde{\nu }$ (13CO) [cm−1]	IR calc. (C 4v+q)[f] $\tilde{\nu }$ (CO) [cm−1]	avg. d(M−C) $[$ Å$]$	avg. d(CO) $[$ Å$]$
[Fe(CO)5 oDFB].+ [Al(ORF)4]−	2083 (vw)[c] 2110 (w) 2116 (w) 2128 (vw)	2090 (vw)[c,d] 2112 (s)[d]	–	–	–	ax.: 1.907(3) eq.: 1.874(5)	ax.: 1.105(3) eq.: 1.118(6)
[Fe(CO)5].+ [Al(ORF)4]− (1)	2082 (vw)[c] 2113 (s) 2128 (w)	2084 (vw)[c,e] 2115 (s)[e]	2102 (100), $v_{eq}$ , E 2102 (100), $v_{eq}$ , E 2106 (48), $v_{ax}$ , A1	2071 (2)[b] 2102 (100)[b]	2063 (100) 2075 (75) 2099 (22) 2141 (26) 2179 (6)	ax.: 1.910(4) eq.: 1.872(5)	ax.: 1.115(5) eq.: 1.126(6)
[Fe(CO)5].+ [F‐{Al(ORF)3}2]− (2)	2084 (vw)[c] 2116 (s)	–	–	–	–	ax.: 1.903(4) eq.: 1.872(4)	ax.: 1.118(4) eq.: 1.118(5)

[a] v: very, s: strong, w: weak. [b] Superposition of the CO‐stretches calculated for a C _4v ground state including the relative contributions of the ¹³C natural abundance isotope. Individual contributions: ¹³CO axial C _4v: A ₁ 2061 (43), E 2102 (100), B ₁ 2120 (0), A ₁ 2168 (3) and ¹³CO equat. 2065 (73), 2102 (100), 2106 (50), 2115 (19), 2164 (3). [c] Probably the ¹³CO stretch. [d] Measured in oDFB. [e] Measured in 4FB. [f] Calculated CO bands in the presence of −0.3e point charges obtained from scXRD.