Syntheses of Iron(0) Complexes of Symmetrical Trialkylphosphines with Three Terminal Vinyl Groups, P((CH2)mCH=CH2)3

Abstract

Reactions of (BDA)Fe(CO)3 (BDA = benzylideneacetone) and P((CH2)mCH=CH2)3 (1; m = 4, a; 5, b; 6, c; 7, d; 8, e) give the trigonal bipyramidal bis(phosphine) complexes trans-Fe(CO)3(P((CH2)mCH=CH2)3)2 (2a–e) as moderately air-sensitive yellow-orange oils in 60–75 % yields after workup. These and NO+BF4– react to give the cationic iron dicarbonyl nitrosyl complexes trans-[Fe(CO)2(NO)(P((CH2)mCH=CH2)3)2]+BF4– (3a–e; orange oils, 88–98 %). Further substitution is effected with n-Bu4N+X– (X = Cl, Br, I, or CN) to give trans-Fe(CO)(NO)(X)(P((CH2)mCH=CH2)3)2 (4a–e-X; red oils, 73–93 %). The NMR (1H, 13C, 31P) and IR properties of these adducts, which provide precursors to gyroscope-like complexes by intramolecular C=C metatheses, are analysed in detail.