ArticleOrganometallics,Vol.29,No.13,2010

Table1.Selected1H,13C{1H},and31P{1H}NMRandIRDataforComplexes5a-dand9a-d

31

2919

P{1H}(ppm)

H1

1

H(ppm)H39.098.337.987.957.797.827.567.83

H517.4017.4516.3616.4516.6216.6816.6216.52

C1254.70253.76259.75253.67233.40232.45233.16233.01

C2114.40115.46119.72114.32115.48115.36115.35116.04

13

C{1H}(ppm)

C4115.36116.86120.41116.11136.53136.38136.42136.34

C5240.35238.03245.35240.12251.94265.09251.70251.89

NtC143.15143.34145.15144.06153.18141.78156.22156.21

IR(cm-1)NtC20952109208120882084208620752064

compd5a5b5c5d9a9b9c9d

a

C3153.74152.76158.91152.89139.47139.69139.28139.58

20.64,25.58,-1.4819.74,24.88,-1.2020.59,25.48,-1.8320.65,25.36,-1.4718.68,-3.3418.57,-3.0117.00,-5.1818.67,-2.1215.6915.7414.6214.5413.7313.7713.6713.63

Numberingschemesforthehydrogenandcarbonatomsin5a,band9a,b

are

SynthesisandCharacterizationof1,4-Phenylenediisocya-nide-BridgedBisosmafuran.Metallafurans,aclassoffive-memberedmetallacycles,arealsoacommonrepresentativeofmetalla-heteroaromaticcompounds.Asacomparativestudy,wehavealsopreparedadiisocynide-bridgedbisosma-furanvialigandsubstitutionreaction.Inamannersimilartothatfor5a-d,treatmentatroomtemperatureofosmafuran[Os(CHC(PPh3)C(OEt)O)Cl2(PPh3)2](6)23with0.5equivof1,4-phenylenediisocyanideinthepresenceofNH4PF6over10hresultedintheformationof1,4-phenylenediisocyanide-bridgedbisosmafurancomplex7,whichwasisolatedasalightyellowsolidaftercolumnchromatographyin78%yield(Scheme2).Althoughstableinthesolidstate,asolutionofcomplex7inCH2Cl2canalsoslowlydecomposeatroomtemperatureunderaninertatmosphere.

Complex7hasbeencharacterizedby1H,31P{1H},and13

C{1H}NMR.Thespectroscopicdataareconsistentwithourproposedstructuralformulation.AsinferredfromtheNMRdata,italsocontainstwosymmetricallyrelatedunits.The31P{1H}NMRspectrumshowstheCPPh3signalatδ=14.83ppmandtheOsPPh3signalatδ=10.23ppm,respec-tively,indicatingthetransdispositionofthetwophosphineligands.The1HNMRspectrumshowsthecharacteristicOsCHsignalasadoubletatδ=12.73ppmwithaH-Pcouplingconstantof12.4Hz.Again,incomparisontothatin5,complex7displaysanappreciablyupfieldshiftinreso-nancesfortheortho-protonstoOsontheosmafuranrings,consistentwithincreasedπ-back-bondingbetweenthemetalsandtheisocyanogroupsin6.Inthe13C{1H}NMRspectrum,thesignalsforthemetallacyclecarbonsareobservedat239.51,181.50,and98.81ppm,respectively.Thesignalsoftheethylgroupsappearatδ=64.41and13.50ppm.The13CNMR

(23)Lin,Y.;Gong,L.;Xu,H.;He,X.;Wen,T.B.;Xia,anometallics2009,28,1524.

resonancesoftheisocyanogroupsappearasasingletatδ=145.73ppm.

SynthesisandCharacterizationofDiisocyanide-BridgedBisosmabenzenesfromNucleophilicAdditionReactions.InourpreviousstudyonthereactionofOsCl2(PPh3)3withterminalalkyneHCtCCH(OH)CtCH,whichresultedintheformationoftheosmabenzene[Os(CHC(PPh3)CHC-(PPh3)CH)Cl2(PPh3)2]OH(3),wehavesucceededinisolat-ingakeyintermediate,theosmacycle-containingcoordi-natedalkynealcohol[Os(CHdC(PPh3)CH(OH)-η2-CtCH)Cl2(PPh3)2](8).5n,21Ithasbeenfoundthattheisolatedcomplex8cannotonlyreadilyreactwithPPh3toproducethediphosphoniumosmabenzene3butalsoreactwithothernucleophilessuchasI-andSCN-togivemonophospho-nium-substitutediodo-aswellasthiocyanato-osmabenzenesvianucleophilicattackatthecoordinatedalkyne.5nThere-fore,wewerepromptedtoattemptconstructionofbisosma-benzenesdirectlyfromthereactionsof8withdiisocyanidesinthepresenceofnucleophile.Withthisstrategy,asshowninScheme3,bisosmabenzenes9a-dcouldbeproducedfromthereactionsof8withasolutionofdiisocyanideligands4a-dinthepresenceofNH4PF6andNaCl.Aftercolumnchromatography,9a-dwereisolatedasgreenishsolidsinmodestyieldsrangingfrom47%to67%.Again,NH4PF6wasaddedtoabstractoneofthechlorideligandsin8toacceleratethereaction,whiletheaddedNaClcanprovidesufficientnucleophilesinthereactionmedia,whichcanimprovetheyields.Additionofexcessisocyanideligandledtotheformationofunidentifiedinsolubleproduct,prob-ablysomepolymericspecies.Itshouldbenotedthatcom-plexes9a-dshowexcellentthermalstabilityunderN2atmosphereinsolidstate,inviewofthefactthatthesolidsampleremainsalmostunchangedwhenheatedat120οCunderaninertatmosphereover10h.Unlikebisosmaben-zenes5a-d,thesecomplexesarestableinCH2Cl2solution