Addition of hexafluorobut-2-yne to tricarbonyl(cycloheptatriene)iron; crystal structure of a phosphite derivative of the 2: 1 adduct, [Fe(CO)2{P(OCH2)3CMe}(C7H8)(C4F6)2]

Abstract

An X-ray crystallographic investigation of the structure of [Fe(CO)₂{P(OCH₂)₃CMe}(C₇H₈)(C₄F₆)₂] has revealed that the addition of hexafluorobut-2-yne to [Fe(CO)₃(C₇H₈)] takes place in the molar ratio 2: 1 and that this addition is endo to the iron atom. A quadricyclic structure is generated, comprising the original seven-membered ring, two new five-membered rings, and a three-membered bridge ring. A possible mechanism of formation is discussed. Crystals are monoclinic, space group P2₁/n, with Z= 4 in a unit cell of dimensions a= 8.647(3), b= 29.650(9), c= 9.371(3)Å, β= 92.87(3)°. The structure has been solved by heavy-atom methods from 3 093 independent observed intensities measured on a four-circle diffractometer, and refined to R 0.055 (R′ 0.064).