Synthesis and Characterization of Stable Ruthenabenzenes Starting from HC⋮CCH(OH)C⋮CH

Treatment of RuCl2(PPh3)3 with HC⋮CCH(OH)C⋮CH/PPh3 at room temperature produces the air-stable ruthenabenzene [Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PPh3)2]Cl (2) in good yield. The ruthenabenzene
2 can even be obtained from the one-pot reaction of RuCl3, PPh3, and HC⋮CCH(OH)C⋮CH in the
mixed solvent of ionic liquid and CH2Cl2 in higher yield. The ruthenabenzene 2 reacts with PMe3, PBu3,
tert-butyl isocyanide, 2,2‘-dipyridyl (bipy), and 2,2‘-dipyridyl/PMe3 to give new stable ruthenabenzenes
[Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PMe3)2]Cl (4), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PBu3)2]Cl (5), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl(tBuNC)(PPh3)2]Cl2 (6), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl(bipy)(PPh3)]Cl2
(7), and [Ru(CHC(PPh3)CHC(PPh3)CH)(bipy)(PMe3)2]Cl3 (8), respectively. Reaction of ruthenabenzene
2 with AgBF4 gives bisruthenabenzene [Ru(CHC(PPh3)CHC(PPh3)CH)(PPh3)]2(μ-Cl)3(BF4)3 (9). The
thermal decomposition reactions of ruthenabenzene 2 and 7 produce a stable Cp- ion derivative, [CHC(PPh3)CHC(PPh3)CH]Cl (10). 2, 4, 7, 8, 9, and 10 have been structurally characterized. 9 is the first
non-metal-coordinated bismetallabenzene. An electrochemical study shows that the metal centers in the
bisruthenabenzene 9 slightly interact with each other through the chloro bridges.