posted on 2017-06-02, 20:16authored byMateusz K. Cybulski, Jessica E. Nicholls, John P. Lowe, Mary F. Mahon, Michael K. Whittlesey
The all-trans isomer of Ru(IMe4)2(PPh3)2H2 (ttt-4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene)
reacts with C6F6 at 70 °C to afford the
hydride fluoride complex Ru(IMe4)2(PPh3)2HF (ttt-6). At room temperature, ttt-6 reacts with Et3SiH to give a
mixture of products, one of which is assigned as the silyl trihydride
complex Ru(IMe4)2(PPh3)(SiEt3)H3 (8) by comparison to the isolated
and structurally characterized analogue Ru(IMe4)2(PPh3)(SiPh3)H3 (9).
As ttt-4 was re-formed cleanly upon heating ttt-6 with Et3SiH, it was tested in the catalytic
hydrodefluorination (HDF) of C6F6 (10 mol %,
90 °C), along with 9, Ru(IMe4)2(P-P)HF (P-P = Ph2P(CH2)2PPh2 (dppe, cct-13), Ph2P(CH2)3PPh2 (dppp, cct-14), Ph2PCH2PPh2 (dppm, cct-15)), Ru(IEt2Me2)2(PPh3)2HF (cct-7; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)),
and Ru(IEt2Me2)2(dppe)2HF (cct-16) for comparison. Both cct-13 and cct-14 brought
about near-quantitative conversion to C6FH5 in
24 h, in comparison to ca. 50% conversion with ttt-4 in
144 h.