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.