VOLTAMMETRIC, SPECULAR REFLECTANCE INFRARED, AND X-RAY ELECTRON-PROBECHARACTERIZATION OF REDOX AND ISOMERIZATION PROCESSES ASSOCIATED WITHTHE [MN(CO)(2)(ETA(3)-P2P')BR](+ 0) (P2P'=(PH2P(CH2)(2))(2)PPH), [MN(CO)(2)(ETA(3)-P3P')BR](+/0) (P3P'=(PH2PCH2)(3)P), AND [(MN(CO)(2)(ETA(2)-DPE)BR)(2)(MU-DPE)](2+/0) (DPE=PH2P(CH2)(2)PPH2) SOLID-STATE SYSTEMS/

Extremely well defined voltammetric responses are obtained for both ox idation of microcrystalline mononuclear trans- and cis,mer-Mn(CO)(2)(e ta(3)-P2P')Br (P2P' = {Ph2P(CH2)(2)}(2)PPh) and cis,mer-Mn(CO)(2)(eta( 3)-P3P')Br (P3P' = {Ph2PCH2}(3)P) and binuclear cis,fac-{Mn(CO)(2)(eta (2)-dpe)Br}(2)(mu-dpe) (dpe = Ph2P(CH2)(2)PPh2) and reduction of catio nic trans-[Mn(CO)(2)(eta(3)-P2P')Br]BF4, trans-[Mn(CO)(2)(eta(3)-P3P') Br]BF4, and ans-[{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)](BF4)(2) when th ey are attached to a graphite electrode and placed in water containing either 0.1 M NaCl or KCl as the electrolyte. The combination of acces s to species in different oxidation states and different isomeric form s, as well as mononuclear and binuclear species, enables the rates of isomerization and the extent of electronic communication between the m etal centers to be evaluated in the solid state and compared to data i n organic solvent systems previously reported. The voltammetric data, combined with specular reflectance IR and X-ray electron probe data, e stablished that the following processes occur at the graphite electrod e-microcrystal-water (electrolyte) interface (subscript ''s'' denotes solid): trans-Mn(CO)(2)(eta(3)-P2P')Br-s + Cl- reversible arrow trans- [Mn(CO)(2)(eta(3)-P2P')Br]Cl-s + e(-); cis,mer-Mn(CO)(2)(eta(3)-P2P')B r-s + Cl- reversible arrow cis,mer-[MN(CO)(2)(eta(3)-P2P')Br]Cl-s + e( -) --> trans-[Mn(CO)(2)(eta(3)-P2P')Br]Cl-s; trans-Mn(CO)(2)(eta(3)-P3 P')Br-s + Cl- reversible arrow trans-[Mn(CO)(2)(eta(3)-P3P')Br]Cl-s e(-); cis,mer-Mn(CO)(2)(eta(3)-P3P')Br-s + Cl- reversible arrow cis,me r-[Mn(CO)(2)(eta(3)-P3P')Br]Cl-s + e(-) --> trans-[Mn(CO)(2)(eta(3)-P3 P')Br]Cl-s; trans-{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)(s) + 2Cl(-) rev ersible arrow trans-[{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)]Cl-2 s + 2e( -); cis,fac-{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)(s) + 2 Cl- reversible arrow cis,fac-[{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)]Cl-2 s + 2e(-) -- > trans-[{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)]Cl-2 s. The reaction pat hways in organic solvents are generally analogous. However, the rates of isomerization are slower in the solid state, and shapes of voltammo grams and potentials differ significantly. Interestingly, in the binuc lear [{Mn)CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)](2+/0) system, no intermedi ate [{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)](+) species are observed in the solid state, implying that the metal centers are oxidized or reduc ed at the same potentials, unlike the case in the solution phase, wher e the [{Mn(CO)(2)(eta(2)-dpe)Br}(2)(mu-dpe)](2+/+) and [{Mn(CO)(2)(eta (2)-dpe)Br}(2)(mu-dpe)](+/0) redox couples are well separated. This re sult implies that no significant communication occurs between the meta l centers in the solid state redox processes.