Photocatalytic properties of new cyclopentadienyl and indenyl rhodium(I) carbonyl complexes with water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) and tris(2-cyanoethyl)phosphine

Reactions of [(η5-R)Rh(CO)2] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh(η5-cp)(CO)(PTA)] (1), [Rh(η5-cp)(CO)(P(CH2CH2CN)3)] (2), [Rh(η5-ind)(CO)(PTA)] (3) and [Rh(η5-ind)(CO)(P(CH2CH2CN)3)] (4) in isolated yields of 52–75%. All these compounds have been fully characterized by IR, 1H, 31P{1H} and 13C{1H} NMR, FAB-MS spectroscopies and elemental analyses. Reactivity for the substitution of phosphine is greater for [(η5-ind)Rh(CO)(L)] comparing to [(η5-cp)Rh(CO)(L)] because of a flexibility of the indenyl ligand to undergo facile η5–η3 coordinative isomerizations. The obtained complexes are active catalyst precursors for the dehydrogenation of propan-2-ol, octane and cyclooctane under photoassisted conditions without any organic hydrogen transfer acceptors, giving TOFs of 26–56 using 3 as precatalyst.

Graphical abstractReactions of [(η5-R)Rh(CO)2] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh(η5-cp)(CO)(PTA)], [Rh(η5-cp)(CO)(P(CH2CH2CN)3)], [Rh(η5-ind)(CO)(PTA)] and [Rh(η5-ind)(CO)(P(CH2CH2CN)3)] in isolated yields of 52–75%. The obtained complexes are precursors of active catalysts for dehydrogenation of saturated compounds under photoassisted conditions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesized cyclopentadienyl and indenyl rhodium(I) complexes are water soluble. ► Reactivity of [(η5-ind)Rh(CO)(L)] is higher comparing to [(η5-cp)Rh(CO)(L)]. ► Complexes catalyse dehydrogenation under photoassisted conditions.