Nucleophilic Addition of Alcohols to [Fe₂(CO)₆(μ-PPh₂){μ-η¹:η²_αβ-(R)C_αC_βC_γH₂}] (R = H, Ph):  Generation of the Binuclear β,γ-Unsaturated Esters [Fe₂(CO)₅(μ-PPh₂)(μ-η¹(O):η¹(C):η²(C)-{R¹O(O)CCH₂}CCH₂)] (R¹ = Me, Et, ⁱPr)

Abstract

Nucleophilic addition of alcohols to the μ-η1:η2-allenyl complexes [Fe2(CO)6(μ-PPh2){μ-η1:η2αβ-(R)CαCβCγH2}] (R = H, 1a; R = Ph, 1b) occurs exclusively via a carbonyl−alcohol−allenyl coupling sequence to afford the binuclear β,γ-unsaturated esters [Fe2(CO)5(μ-PPh2)(μ-η1(O):η1(C):η2(C)-{R1O(O)CCHR}CCH2)] (2a, R = H, R1 = Me; 2b, R = H, R1 = Et; 2c, R = H, R1 = iPr; 2d, R = Ph, R1 = Me) which contain a five-membered metallacycle by virtue of coordination of the ester carbonyl. Trimethyl phosphite readily substitutes the metal-coordinated ester carbonyl of 2a−c to afford the ester-functionalized μ-η1:η2-alkenyl complexes [Fe2(CO)5{P(OMe)3}(μ-PPh2)(μ-η1:η2-{R1O(O)CCH2}CCH2)] (3a, R1 = Me; 3b, R1 = Et; 3c, R1 = iPr). The X-ray structures for 2c, 2d, and 3c are reported.