Triferriothioxophosphoranes: First Structural Characterization of a μ 3 ‐P=S Complex

The P‐H‐functional triferriophosphonium salts [{CpFe‐(CO) 2 } 3 PH] 2 FeCl 4 ( 1 ) and [{μ‐CO(CpFeCO) 2 }{CpFe‐(CO) 2 }PH] 2 FeCl 4 ( 4 ) are easily deprotonated by DBU to the corresponding unstable triferriophosphanes 2, 5 , which subsequently are oxidized by sulfur to the triferriophosphane sulfides {CpFe(CO) 2 } 3 P=S ( 3 ) and {μ‐CO(CpFeCO) 2 }{CpFe‐(CO) 2 }P=S ( 6 ), respectively. The photolysis of 3 results only in its decomposition by elimination of [CpFe(CO) 2 ] 2 , whereas the photolysis of 6 cleaves off one CO ligand to give the new spiro compound (CpFeCO)(μ‐η 2 ‐PS){μ‐CO(CpFeCO) 2 } ( 7 ), where the P=S unit is η 2 ‐bonded to the 15‐electron CpFeCO fragment, and the phosphorus atom bridges two 17‐electron fragments. Compound 7 shows a new coordination mode of the PS unit where sulfur is also bound to one of the metal atoms. Compounds 6 and 7 can be regarded as first examples of a new class of PS complexes of transition metals. All compounds were characterized by IR, 31 P{ 1 H}‐ and 13 C{ 1 H}‐NMR spectroscopy as well as mass spectrometry; for 6 the X‐ray analytical data are given.