Photoinduced Reactions of Diruthenium Tetrahydride Complexes: Carbon–Hydrogen Bond Cleavage of Tetrahydrofuran Leading to Bridging Cyclic Fischer-Type Carbene Complexes

Abstract

Photochemical reactions of diruthenium tetrahydride complexes containing cyclopentadienyls as auxiliary ligands, CpsRu­(μ-H)4RuCps (1) (a: Cps = C5Me5 (Cp*), b: C5EtMe4 (CpEt), and c: 1,2,4-C5(t-Bu)3H2 (Cp‡)), with tetrahydrofuran were studied for elucidation of the reaction mode of dinuclear complexes containing multiple bridging hydrides. Complexes 1a–c reacted with tetrahydrofuran under UV irradiation (365 nm) to produce bridging cyclic Fischer-type carbene complexes, {CpsRu­(μ-H)}2(μ-cyclo-CCH2CH2CH2O−)­(μ-H)2 (5), via consecutive C–H bond cleavage at the α-position of the oxygen atom. The characteristic cyclic structures of the bridging carbene ligands were unambiguously confirmed by X-ray diffraction studies. Line-shape analysis of the variable-temperature 1H NMR spectra of 5c demonstrated the rotation of the bridging carbene ligand.

σ-Coordination of a P–H Bond at a Sterically Demanding Diruthenium Site: Tautomerization between Agostic μ-Phosphane and μ-Phosphanido Complexes via an η2-P–H Bond Cleavage

“…This can alter the reaction mechanism and often provides very active species, as seen in the field of palladium phosphane chemistry . We reported the synthesis of a diruthenium complex, Cp ‡ Ru­(μ-H) 4 RuCp ‡ ( 1 ; Cp ‡ = 1,2,4-C 5 t Bu 3 H 2 ), supported by bulky Cp ‡ groups, whose steric demand effectively prevented the condensation of the dinuclear complex to a tetranuclear skeleton …”

“…t Bu 3 H 2 ), supported by bulky Cp ‡ groups, 2 whose steric demand effectively prevented the condensation of the dinuclear complex to a tetranuclear skeleton. 3 Steric repulsion also influences the coordination mode of substrates at a multimetallic site. We have shown that a triruthenium complex, {Cp*Ru(μ-H)} 3 (μ 3 -H) 2 (Cp* = C 5 Me 5 ), reacts with primary silanes to yield an equilibrated mixture of μ 3 -η 2 :η 2 :η 2 -silane and μ 3 -η 2 :η 2 -silyl complexes.…”

Photochemistry of Transition Metal Hydrides

“…9,10 The past few years have also seen important progress in the photochemistry of complexes with bridging hydrides. 11,12 The production of hydrogen by photocatalytic methods is of enormous current interest, but the vast majority of approaches involve neither photochemical reaction of metal hydride complexes directly nor formation of excited states of metal hydride complexes by photosensitization. The involvement of hydrides in the photocatalytic splitting of water, typically by protonation of an intermediate, is reviewed elsewhere, 13−17 and a very different approach will be taken here.…”

Dehydrogenative Oxidation of Cyclic Amines on a Diruthenium Complex

“…We speculate that the formation of catalytically inactive species as a consequence of oxygen atom directed reactions is responsible for this failed reaction. We have previously shown that 1 reacts with tetrahydrofuran to yield a μ-oxycarbene complex …”

“…We have previously shown that 1 reacts with tetrahydrofuran to yield a μ-oxycarbene complex. 11 The stoichiometric reaction of 1 with cyclic amines was then investigated to elucidate the mechanism. Complex 1 reacted with hexamethylenimine at 160 °C to afford the μ-cyclic imine complex 2 in 71% yield (eq 1).…”