2922Organometallics,Vol.29,No.13,2010Table2.CyclicVoltammetryDataforComplexes9a-din

CH2Cl2Containing0.1Mn-Bu4NClO4a

potentialdata/V

Ep,a,1

Ep,c,1ΔEp,1Ep,a,2Ep,c,2ΔEp,29a1.221.070.159b1.221.080.149c0.580.380.200.770.590.199d

0.160.010.15

0.81

0.65

0.16

a

PotentialversusAg/AgCl,scanrate=0.10Vs-1

.

anyelectronicinteractionbetweenthemetalcentersincomplex9a.Itislikelyascribedtorotationoftwoconjoiningbenzeneringsincomplex9a26,whichbreakstheπ-conjugatedelectroniccommunication.Additionally,anadsorptionprewave(AI)canbeseenintheCVofcomplex9a,indicatingthatreactant9acanbestronglyadsorbedontheglassycarbonelectrode.27Similaradsorptionpeaksfortheoxida-tionof9bcanbealsoobservedinFigures2and3.Theredox

(26)(a)Ghazala,S.I.;Paul,F.;Toupet,L.;Roisnel,T.;Hapiot,P.;Lapinte,C.J.Am.Chem.Soc.2006,128,2463.(b)Xia,J.-L.;Wu,X.;Lu,Y.;Chen,G.;Jin,S.;Yu,G.;Liu,anometallics2009,28,2701.(27)Wopschall,R.H.;Shain,I.Anal.Chem.1967,39,1514.

Huangetal.

Figure4.Cyclic(a)anddifferentialpulse(b)voltammogramsofcomplex-9c1inCH2Cl2with0.1Mn-Bu4NClO4atascanrateof0.10Vs.

performanceof9bissimilartothatof9a.Again,noelectro-nicinteractionbetweenthetwoosmiumcentersforcomplex9bwasobserved,whichmightbeduetothelackofconjuga-tionin9b.

Interestingly,forcomplex9c,withanoxygenatomin-sertedbetweentwo1,4-phenylenegroupsofcomplex9a,aweakbutappreciableelectronicinteractionbetweenthemetalcenterscanbeobserved(Figure4).ThetwooxidationwavesatEp,a=þ0.58VandEp,a=þ0.77VarepartlyoverlappedandtheΔEforcomplex9cisfoundtobe0.19V,indicatingthepresenceofastrongerinteractionbetweenthetwometalcentersin9cthanthatin9a.Undoubtedly,animportantcontributoristhepresenceofalonepairofelectronsontheoxygenatom,28whichprovidesarelativelysoftsetofdelocalizedformsthroughwhichtheincreaseinthepositivechargeuponoxidationmaybefeltbyoneOsunitfromtheother,thereforegivingrisetoaconsiderableincreaseininternuclearcommunicationbetweenthetwoOsunits.

Asexpected,amoderatemetal-metalinteractionisclearlyobservedinbismetallabenzene9dthroughthe1,4-phenylene-diisocyanidebridge.AsshowninFigure5,9dundergoestwoconsecutive,chemicallyandelectrochemically,

one-electron

(28)Rigaut,S.;Olivier,C.;Costuas,K.;Choua,S.;Fadhel,O.;Massue,J.;Turek,P.;Saillard,J.-Y.;Dixneuf,P.H.;Touchard,D.J.Am.Chem.Soc.2006,128,5859.