Synthesis and Structural Study of the (N,N,N′,N′-Tetraethylethylenediamine)CdFe(CO)4 Dimer

The new [(teeda)CdFe(CO)4]2 complex has been isolated from the reaction of with tetraethylethylenediamine. Unlike previous structural reports of ligand adducts of complexes, which have all been trimeric species composed of six-membered Cd3Fe3 rings, the teeda complex crystallized as a dimer, analogous to [(2,2-bpy)ZnFe(CO)4]2. As in the zinc dimer, significant distortion arises from steric interactions between the axial carbonyl ligands on opposing iron centers. The complex sits on an inversion center, leading to two independent Cd–Fe distances, 2.7244(6) and 2.7433(6) ？, and crystallizes in the monoclinic space group P21/a with a = 14.8546(2) ？, b = 15.1647(3) ？, c = 15.5252(3) ？, β = 90.9517 , and = 1.719？g/cm3 at 150(1)？K. 1. Introduction While cadmium iron carbonyl complexes have been known since at least 1933 [1, 2], only a few of these [ CdFe(CO)4]x complexes have been structurally characterized, with L being THF or a variety of aromatic amines. For L being pyridine or THF [3] or L2 being 2,2′-bipyridine (bpy) [4], trimeric species, having , have been observed, though [(bpy)ZnFe(CO)4]2 adopts a dimeric (four-membered ring) structure [5] (Figure 1). In addition, some more complicated species such as Cd[Fe2(CO)8]2？ [6], Cd[Fe3(CO)11]2？ [7], [(Cd4Cl6)Fe(CO)4(THF)5], and [8] have been reported. A clear question that these studies have tried to address is what factors control the extent of oligomerization, and potentially polymerization, of these species. In order to better understand these factors, it appears necessary to expand upon the types of molecules being studied. As structural data for alkyl amine complexes have thus far not been reported, it was of interest to examine such species. While an = en (ethylenediamine) complex has been reported [2], its low solubility in noncoordinating solvents does not make this compound conducive to crystallization. The use of tetramethylethylenediamine also did not lead to a particularly soluble species, and, as a result, use was made of tetraethylethylenediamine, (C2H5)2NC2H4N(C2H5)2 (teeda), which did lead to a nicely soluble species that could be readily crystallized. Figure 1: Structural arrangements in dimeric and trimeric [ MFe(CO) 4] x complexes ( ). 2. Materials and Methods 2.1. Synthesis All reactions were carried out in Schlenk apparatus under a nitrogen atmosphere. THF was dried by distillation from sodium benzophenone ketyl under nitrogen. All nonmetallic reagents were obtained commercially. A Schlenk flask was charged in a glove box with 0.50？g (1.6？mmol) of [(NH3)2CdFe(CO)4]x [2]. After the flask