Protonation of η⁵-Indenyl Ruthenium Hydride Complexes (η⁵-C₉H₇)Ru(L₂)H and η⁵−η⁶ Haptotropic Rearrangement. X-ray Crystal Structures of (η⁵-C₉H₇)Ru(dppm)H and [(η⁶-C₉H₈)Ru(dppp)H]⁺

Abstract

Protonation of indenyl complexes (η 5 -C 9 H 7 )Ru(dppm)H and (η 5 -C 9 H 7 )Ru(PPh 3 ) 2 H with CF 3 SO 3 H or HBF 4 ·Et 2 O at −60 °C gives the η 2 -dihydrogen complex [(η 5 -C 9 H 7 )Ru(dppm)(H 2 )] + and the dihydride [(η 5 -C 9 H 7 )Ru(PPh 3 ) 2 H 2 ] +, respectively. Upon warming to room temperature, proton shift from the η 2 -H 2 ligand of the former to the indenyl ligand and subsequent migration of the metal fragment from the five-membered ring to the six-membered ring of the indene ligand results in the formation of the η 6 -indene complex [(η 6 -C 9 H 8 )Ru(dppm)H] + . The PPh 3 analogue [(η 6 -C 9 H 8 )Ru(PPh 3 ) 2 H] + is formed in a similar fashion, but in this case, the proton shift is from Ru−H to the indenyl ligand. Low-temperature acidification of (η 5 -C 9 H 7 )Ru(dppe)H and (η 5 -C 9 H 7 )Ru(dppp)H yield mixtures of η 2 -dihydrogen complex and dihydride in both cases. Similar to the dppm and PPh 3 analogues, η 6 -indene complexes [(η 6 -C 9 H 8 )Ru(dppe)H] + and [(η 6 -C 9 H 8 )Ru(dppp)H] + are generated upon warming solutions of the η 2 -dihydrogen complex/dihydride mixtures to room temperature. In the dppp system, the η 5 → η 6 haptotropic rearrangement only occurs after the η 2 -dihydrogen complex → dihydride tautomerization is nearly completed, whereas in the dppe system the two processes seem to occur simultaneously. The parent hydride complexes (η 5 -C 9 H 7 )Ru(L 2 )H can be regenerated upon deprotonation of the η 6 -indene complexes with Et 3 N. Crystal structures of (η 5 -C 9 H 7 )Ru(dppm)H and [(η 6 -C 9 H 8 )Ru(dppp)H] + have been determined by X-ray crystallography; both complexes have three-legged piano-stool structures.