The Fe CO 4 Story

Walsh diagrams for bending triplet Fe(C0)4 toward a tetrahedron (left) and singlet Fe(CO)4to a square plane (right). 

It also must lose its hybridization, but bonding to CO r is turned on. There is again a complicated intermixing between l0, lo, and 3fl so that ultimately l0 becomes 

ML4 complexes remain at the sawhorse geometry when two CO ligands are replaced by cr-donor phosphines, for example, Ru(CO)2[P(t-Bu)2Me]3)2 [9], 19.8. Here P—Ru—P= 165.6° and C—Ru—C= 133.4°. In other words, the loss of TT-bonding in 19.7 is energetically more important than the gain in 19.6. The structure with four phosphines can be considered to be one with an approximate 

Probably the quintessential transition metal dimer is Re2Cl8 . The discovery of the structure [22] brought a whirlwind of activity in the field of transition metal compounds with multiple M—M bonds [23]. Re2Cla has Re in the - -3 oxidation state and, therefore, each ReCU unit is d . These four d electrons couple to form one a, two TT, and one 8 bonds as shown in 19.23. The overlap of t jr 3 insures that the MO ordering is given by that in 19.23. The 0 and e set are hybridized out toward the 

Along with Fe(CO)4, the Turner group has also studied the low temperature matrix isolation of Fe2(CO)s by photolysis of Fe2(CO)9, 19.27 [28]. Electron counting in 19.27 yields 17 electrons around each Fe, so an Fe—Fe bond should 

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