glove box for 1 hour under argon in the absence of air the solution was filtered hot and upon cooling 250 milligrams of black crystals were filtered off the crystals were redissolved in toluene and recrystallized to purify them hfeco 3 co 10 p c 6 h 5 3 2 mu hydrido iron tricobalt decacarbonyl bistriphenyl phosphine was prepared as for the trimethyl phosphine compound just discussed except for substituting triphenyl phosphine for the trimethyl phosphine other compounds of the family can also be prepared by known procedures for example the ruthenium analog of cyclopentadienyl iron carbonyl tetramer can be prepared by procedures known in the art see t blackmore et al 34 chemistry of the metal carbonyls part liii some dicarbonyl pi cyclopentadienyl ruthenium complexes containing metal metal bonds 34 j chem soc a 1968 pages 2931 2936 test results for the preferred rsa material the other materials prepared in the manner described above and some prior art compounds not related to the present invention are presented in fig6 to conduct these measurements the organometallic cluster compound was dissolved to a concentration of about 5 u00d7 10 4 molar in methylene chloride solvent while the other rsa materials were dissolved in effective solvents a cell was prepared with a length parallel to the axis of measurement of 0 1 1 0 centimeter the length of the cell was selected such that about 75 percent of the light was absorbed in the rsa material but that length was small about 0 1 centimeters for the compounds of the invention and chloroaluminum phthanocyanine and large about 1 0 centimeter.