Selenophosphine Derivatives with Pendant Electron-Rich Fe(κ2‑dppe)(η5‑C5Me5)CC– Substituents

Five new selenophosphines (5a–d and 7) bearing organometallic Fe­(κ2-dppe)­(η5-C5Me5)­CC– substituents were synthesized and structurally characterized in order to determine the steric and electronic parameters of the parent metallo-phosphines (1a–d and 2). Their cone angles were estimated from available structural data, and their electronic parameters were derived from the 1JPSe coupling constants. DFT calculations suggest that 1JPSe constants can be used to determine their electronic parameters in spite of the existence of the low-lying excited states for 5a–d. Strong solvent effects were evidenced on 1JPSe, stressing the need to use a single solvent (CDCl3) for measuring these coupling constants if comparison of the electronic parameter of these with existing data is sought. Among the parent metallo-phosphines, 2 appears to be the most electron donating ligand by far. According to its 1JPSe value, it resembles a tris­(alkyl)­phosphine but presents a significantly larger Tolman cone angle (θT ≈ 172°) than PPh3 (θT ≈ 145°).