Rhenium complexes monodentate phosphines

The coordination chemistry of the hydrido/phosphine rhenium complexes can be extended to phosphonite and phosphite complexes. This has been demonstrated for monodentate ligands such as P(OEt)3, P(OCH2)3CEt and PPhtORE (R = Me, Et, Pri),2S8779,809,iii8 chelating phos-... 

Complexes of the general formula /ac-Re(a-diimine)(CO)3X and Re(a-diimine)(CO)2XX (where ot-diimine = bpy, phen, substituted bpy or phen, etc. and X, X = halide, solvent, alkyl, benzyl, monodentate phosphine, CO, etc.), have attracted interest since the mid-1970s [51-53]. Many of these complexes show emission from their lowest long-lived MLCT state at room temperatme in solution. Their catalytic properties for CO2 reduction have also been investigated. Electrolysis of a solution containing/uc-Re(bpy)(CO)3 Cl and 0.1 M BU4NPF6 in freshly distilled C02 saturated MeCN at —1.5 V (vs. SCE) produces both CO and C03 with cmrent efficiencies of 98 and 110 %, respectively [54]. Further, yhc-Re(bpy)(CO)3X (X = Cl, Br ) has been used successfully as a photocatalyst for CO2 reduction to CO with TEOA in DMF [55-58]. When X = Cl , a quantiun yield of 0.14 has been measured in the presence of excess Cl". A formato-rhenium complex,/ac-Re(bpy)(C0)3(02CH), has been isolated in the absence of excess Cl". 

The rich and diversified rhenium chemistry developed with the PNX (X is O, S) phosphines motivated the authors to explore their use in the so-called 3+1 approach [58,59]. Different model complexes, 55-58, were synthesized by reacting [NBuJ [ReOClJ with H2PNO or with H2PNS in the presence of several monodentate thiols as coligands (Scheme 13) [58]. 

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