REDUCTION-OXIDATION PROPERTIES OF ORGANO-TRANSITION METAL-COMPLEXES .33. LIGAND-METAL-BASED VS METAL-BASED OXIDATION OF CYANO-BRIDGED CATECHOLATORUTHENIUM MANGANESE CARBONYL-COMPOUNDS - THE X-RAY CRYSTAL-STRUCTURE OF CIS-[(DPPE)(ET3P)(OC)2MN(MU-CN)RU(CO)2(PPH3)(O-O2C6CL4)].CH2CL2

The reactions of cis- or trans-[Mn(CN)(CO)2{P(OPh)3}(dppm)] (dppm = Ph2PCH2PPh2) or cis-[Mn(CN)(CO)2(PEt3)(dppe)] (dppe = Ph2PCH2CH2PPh2) with [{Ru(CO)2(PPh3)(mu-omicron-O2C6Cl4)}2] give the heterobinuclear complexes cis- and trans-[(dppm){(PhO)3P}(OC)2Mn(mu-CN)Ru(CO)2(PPh3)(omicron-O2C6Cl4)] 5 and 6 and cis-[(dppe)(Et3P)(OC)2Mn(mu-CN)Ru(CO)2(PPh3)(omicron-O2C6Cl4)] 7. The X-ray crystal structure of 7 shows approximately octahedrally co-ordinated ruthenium and manganese centres linked by a mu-CN ligand C-bonded to Mn and N-bonded to Ru, the Ru-N-C-Mn system is slightly non-linear, with angles at C and N of 174.8(5) and 171.4(4)-degrees, despite the formal sp hybridisation at these atoms. Complexes 5-7 undergo two sequential one-electron oxidations at a platinum electrode in CH2Cl2. Treatment with 1 equivalent of [NO][PF6] gives the monocations cis- and trans-[(dppm){(PhO)3P}(OC)2Mn(mu-CN)Ru(CO)2(PPh3) (omicron-O2C6Cl4)] + 5+ and 6+ and cis-[(dppe)(Et3P)(OC)2Mn(mu-CN)Ru(CO)2(PPh3)(omicron-O2C6CL4)] + 7+ the voltammetry and IR and ESR spectra of which show electron removal from the catecholate ligand. The reaction of [{Ru-(CO)2(PPh3)(mu-omicron-O2C6Cl4)}2] with trans-[Mn(CN)(CO)2{P(OPh)3}(dppm)] + also gave 6+ but the analogous reaction with trans-[Mn(CN)(CO)2(PEt3)(dppe)] + 7+. In both cases, intramolecular electron transfer from the O,O-chelate to Mn(II) follows cyanide-bridge formation; in the second case this is accompanied by trans-cis isomerisation at the resulting manganese(I) centre. Subsequent oxidation of 5+-7+ occurs at the manganese(II) centre and is accompanied by cis-trans isomerisation. The reaction of the more electron-rich manganese(I) donor trans-[Mn(CN)(CO)(dppm)2] with [{Ru(CO)2(PPh3)(mu-omicron-O2C6Cl4)}2] gives trans-[(dppm)2(OC)Mn(mu-CN)Ru(CO)2(PPh3)(omicron-O2C6-Cl4)] 8 which also undergoes two one-electron oxidations. In this case, however, oxidation at Mn(I) precedes that at the catecholate ligand; the manganese(II)-containing monocation 8+ is synthesised from 8 and [N2C6H4F-p]+ or directly from [{Ru(CO)2(PPh3)(mu-omicron-O2C6Cl4)}2] and trans-[Mn(CN)-(CO)(dppm)2]+. Changes in nu(CN)bridge appear to be diagnostic of oxidation at the C- or N-bonded centre of the binuclear complexes.