Unexpected formation of a new nitrosylrhenium(II) complex from oxorhenium(V)

Booysen, Irvin Noel; Gerber, Thomas; Mayer, Péter

doi:10.1016/j.inoche.2008.01.017

Cited by 6 publications

(1 citation statement)

References 24 publications

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“…In comparison to the wide variety and scope of d 6 Re(I) coordination compounds, relatively few stable low-spin d 5 Re II monomeric complexes are known. − Heteroleptic diimine and diphosphine carbonyls [(diimine)(CO) 3 ReX] + , , trans -[(PP) 2 (CO) 2 Re] 2+ and trans -[(dppe) 2 (CO)ReBr] + , , have been generated electrochemically and have generally limited stabilities (PP = 1,2-bis(dimethylphosphino)ethane (dmpe), 1,2-bis(diethylphosphino)ethane (depe), bis(dimethylphosphino)methane (dmpm), bis(diphenylphosphino)methane (dppm), Me 2 PCH 2 PPh 2 , 1,3-bis(dimethylphosphino)propane (dmpp), or 1,2-bis(dimethylphosphino)benzene (dmpb); dppe = 1,2-bis(diphenylphosphino)ethane). More recently, [Re(CO) 2 Br 4 ] 2– has been reported as a useful precursor for a variety of [Re(CO) 2 Br 2 (L) 2 ] products. − Very few simple homoleptic Re II complexes are known: [(bpy) 3 Re] 2+ (bpy = 2,2′-bipyridine), , [(2,2′-azobipyridine) 3 Re] 2+ , [(dmpe) 3 Re] 2+ , , and most recently the mixed diphosphine chelate systems [(depe) 3– x (dmpe) x Re] 2+ ( x = 0–3) …”

Section: Introductionmentioning

confidence: 99%

Homoleptic Tris-Diphosphine Re(I) and Re(II) Complexes and Re(II) Photophysics and Photochemistry

Adams¹,

Arulsamy²,

Sullivan³

et al. 2015

Inorg. Chem.

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The ligand-to-metal charge transfer state (LMCT) of [(dmpe)3Re](2+) (dmpe = 1,2-bis(dimethylphosphino)ethane) has been demonstrated to be a potent oxidant (E(0)(Re(2+*)/Re(+)) = 2.61 V vs standard calomel electrode). This complex has been traditionally prepared by nontrivial routes in low yields, and very little has been achieved in optimizing the ground state and emission energy properties of the general class of complexes [(PP)3Re](2+) (PP = chelating diphosphine) through phosphine modification. Improved syntheses for Re(I) tris-homoleptic diphosphine complexes [(PP)3Re](+) (PP = 1,2-bis(dimethylphosphino)ethane (dmpe), 1,2-bis(diethylphosphino)ethane (depe), bis(dimethylphosphino)methane (dmpm), bis(diphenylphosphino)methane (dppm), Me2PCH2PPh2, 1,3-bis(dimethylphosphino)propane (dmpp), or 1,2-bis(dimethyl-phosphino)benzene (dmpb)) were achieved by single-pot reactions exploiting the reducing potential of the phosphines when reacted with Re(V) oxo-complexes in 1,2-dichlorobenzene at 160-180 °C. Single-electron chemical oxidation of [(PP)3Re](+) yields luminescent Re(II) analogues; appropriate use of Ph3C(+), Cp2Fe(+), or (4-BrC6H4)3N(+) B(C6F5)4(-) salts produced [(PP)3Re](2+) complexes in good yields. Crystallographic trends for the Re(+)/Re(2+) pairs show significantly lengthened Re(2+)-P bonds for [(PP)3Re](2+) relative to the corresponding [(PP)3Re](+) system. The redox and luminescence behavior of the complexes indicates the luminescence is from a ligand P(σ)-to-metal (Re(dπ)) charge transfer ((2)LMCT) state for all the complexes. Structured luminescence at 77 K is postulated to originate from relaxation of the (2)LMCT state into two spin-orbit coupled states: the ground state and a state ∼ 3000 cm(-1) above the ground state. The excited-state reduction potential (Re(II*/I)) for [(depe)3Re](2+) was determined from the free energy dependence of luminescence quenching rate constants. Yields for formation of charge separated ions were determined for three of the complexes with a variety of electron donors. Despite favorable electrostatics, no charge separated ions were observed for radical ion pairs for which the energy of back electron transfer exceeded 1.1 V.

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