Ambient‐Temperature Synthesis of 2‐Phosphathioethynolate, PCS(–), and the Ligand Properties of ECX(–) (E = N, P; X = O, S)

A synthesis of the 2‐phosphathioethynolate anion, PCS(–), under ambient conditions is reported. The coordination chemistry of PCO(–), PCS(–) and their nitrogen‐containing congeners is also explored. Photolysis of a solution of W(CO)(6) in the presence of PCO(–) [or a simple ligand displacement reaction using W(CO)(5)(MeCN)] affords [W(CO)(5)(PCO)](–) (1). The cyanate and thiocyanate analogues, [W(CO)(5)(NCO)](–) (2) and [W(CO)(5)(NCS)](–) (3), are also synthesised using a similar methodology, allowing for an in‐depth study of the bonding properties of this family of related ligands. Our studies reveal that, in the coordination sphere of tungsten(0), the PCO(–) anion preferentially binds through the phosphorus atom in a strongly bent fashion, while NCO(–) and NCS(–) coordinate linearly through the nitrogen atom. Reactions between PCS(–) and W(CO)(5)(MeCN) similarly afford [W(CO)(5)(PCS)](–); however, due to the ambidentate nature of the anion, a mixture of both the phosphorus‐ and sulfur‐bonded complexes (4a and 4b, respectively) is obtained. It was possible to establish that, as with PCO(–), the PCS(–) ion also coordinates to the metal centre in a bent fashion.