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Corresponding Author

Shengpei Chen

Abstract

he search for inorganic systems that can cleave N≡N triple bond under mild conditions is an important subject. It is well known that the metal nitrido (M≡N) complexes are possible intermediates in nitrogen fixation [1] and in the reduction of nitrite to ammonia [2,3] . Recently, these complexes have received considerable attention [4~9] for their intriguing photochemical and electrochemical properties. Among different high valence metal nitrido complexes, some osmium(VI) nitrido species are stable enough to be isolated [4~10] , demonstrating that the study on this class of complexes becomes feasible. Meyer and co_workers [4] have reported the electrochemical interconversion between [Os VI (N)(terpy)Cl 2] + and [Os II (NH 3)(terpy)Cl 2] (terpy=2,2':6', 2"_terpyridine). Recently, Che et al. have reported the isolation of an osmium(VI) nitrido complex [Os VI (N)(NH 3) 4Cl] 2+ through oxidation of [Os III (NH 3) 5Cl] 2+[8] . Photolysis of an acetonitrile solution of [Os VI (N)(NH 3) 4](CF 3SO 3) 3 in the presence of an organic electron donor resulted in the formation of the dinitrogen_bridged osmium(II,III) dimer {[Os(NH 3) 4(CH 3CN)] 2(N 2)} 5+[7,8] . It has been found that the one_electron reduced Os V≡N reacts with the starting Os VI ≡N to yield the μ_dinitrogen Os II _N≡N_Os III complex with a second order rate constant of (3.75±0.30)× 10 5 dm 3 mol -1 s -1 in acetonitrile at room temperature [8] . Recently, Taube and co_workers [11] reported that the electrochemical reduction of [Os VI (N)(NH 3) 4] 3+ in acetonitrile resulted also in similar N_N coupling reaction. To our knowledge there is no report, up to now, concerning the in situ FTIR spectroscopic studies of direct coupling of nitrogen atoms of metal nitrido compounds. In the present study, the potential cycling was used to induce the formation of a μ_dinitrogen complex through electrochemical reduction of [Os VI (N)(NH 3) 4](CF 3SO 3) 3 in acetonitrile (donor). The intermediates and products of the reaction on Pt electrode was investigate by means of in situ FTIRS and UV/Vis spectroscopy.

Publication Date

1999-08-28

Online Available Date

1999-08-28

Revised Date

1999-08-28

Received Date

1999-08-28

References

1   Chatt J , Dilw orth J R, Richards R L. Recent advances in the che m istry of nitrogen fixation . Che m . Rev .,1978 ,78 : 589 2   Dehnicke K , Strahle J. Nitrido Co m plexes of Transition Metals , Ange w . Che m ., Int . Ed . En g1 ., 1992 ,31 :955 3   Rhodes M , Meyer T J. Electrocatalytic reduction of nitrite using sim ple coordination co m plexes of iron andrutheniu m . Inorg . Che m ., 198 8 ,27 : 4 772 4   Pipes D W , Bakir M et al . Retersible interconyersion betw een a nitrido co m plex of Os( V I) and an a m mino co mplex of os miu m ( I I) . J. Am .che m .soc . ,1990 , 112 : 5 507 5   Che C M , Lau T Cet al . Metal_nitrido p hoto_oxidants :synthesis , photophysics , and photoche mistry of [ Os V I( N H3) 4( N)] ( X)3( X= C L, C F3 S O3) . J. Che m . Soc ., Che m . Co m m un ., 1989 ,1 14 6   Che C M , La m M H W , Mak T C W . Metal nitrido and lmido photo_oxidants . Photop hysics and photoche mistry of nitrido and lmido co m plexes of os miu m ( V I) and X_ Ray crystal structure of [ Ph4 As] 2[ Os V I( C N) 5 N] . J. Che m . Soc . , Che m . Co m m un . , 1989 , 1 529 7   Che C M , La m H W et al . Model reactions for nitrogen nitrogen fixation . Photo_induced for m ation and X_ Raycrystal structure of [ Os2( N H3) 8( Me C N) 2( N2) ]5 + fro m [ Os V I( N H3) 4 N] 3 + . J. Che m . Soc ., Che m . Co mm un ., 1989 , 1 8 83 8   La m H W , Che C M , Wong K Y. Photoredox properties of [{ Os( N H3)4( C H3 C N)} 2 N2] 5 + through a nitrido_coupling reaction . J. Che m . Soc ., D. alton Trans ., 1992 , 1 411 9   Che C M , Wong K Y et al . Photoredox properties , electroche m istry and crystal structure of mitridoosm iu m( V I) co m plexes of 2 ,3_ Dia mino_2 ,3_dim ethylbutane + . Che m . Soc ., Dalton Trans ., 1993 , 857 10   Sch w ab J J, Wilkinson E C et al . Nitridoos miu m ( V I) and nitridorutheniu m ( V I) co m plexes of cysteine(2_)an d related ligands . J. Am . Che m . Soc ., 1991 ,113 : 6 124 . 11   Wares D Cand Taube H , Substitution_in duced N_ N couplin g for nitride coordinated to os miu m ( V I) . Inorg . Che m ., 1991 ,3 0 : 4 60 12   Buhr J D, Win kler J R , Taube H. Characterization and reactions of os miu m ( I V) a m mines . Inorg . Che m .,1980 ,19 : 2 41 6 . 13   Richardson D E, Sen J Pet al . Preparation and Properties of Mixed_ Valence ( μ_dinitrogen) bis(pentaa m mine)co m plexes of osm iu m and rutheniu m . Inorg . Che m ., 1982 ,21 : 3 13 6 . 14   Mag m uson R H , Taube H. Mixed oxidation states in os miu m a m mine dinlrogen co m plexes . J. Am . Che m . Soc ., 197 2 , 94 :7 213 15   Buhr J D, Taube H . Dinitrogen co m plexes of os miu m ( I I I) haloa m mines . Inorg . Che m ., 19 80 ,19 :2 425

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