摘要：

Synthesis, characterisation, Mossbauer spectra, and structures of sometrinuclear iron-tin clustersChristine J. Cardin," David J. Cardin," Maire A. Convery: Michael M. Devereux,*Brendan Twamley '7' and Jack Silver 'a Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UKDepartment of Chemistry, Trinity College, University of Dublin, Dublin 2, IrelandDepartment of Biological and Chemical Sciences, University of Essex, Wivenhoe Park, ColchesterC043SQ, UKReactions of [Fe,(CO) ,] with diaryltin species SnR, (R ' = 2,4,6-triisopropylphenyl, R2 = 2,6-diethylphenyl,R3 = pentamethylphenyl) and with Sn[CH(PPh,),], have been investigated. The tin reagents SnR, (R = R'or R2) reacted under mild conditions to give in moderate yields the trinuclear species [Fe,(C0)8(p-SnR1,)] 1or [Fez( CO),(p-SnR2,)] 2, as orange-red crystalline solids, which decompose in air on prolonged exposure.The compound [Fe2(CO),(p-SnR4,)] 3 (R4 = 2,4,6-triphenylphenyl) can be similarly obtained. Prolongedtreatment of the carbonyl with the novel tin reagent SnR3,, by contrast, afforded the known compound spiro-[(OC),Fe,SnFe,(CO),] 4 for which data are briefly reported.Reactions with tin or lead reagentsM[CH(PPh,),], (M = Sn or Pb) afforded [Fe2(co),(p-co)(p-dppm)] [dppm = 1,2-bis(diphenylphosphino)methane] rapidly and almost quantitatively. Full crystal and molecular structural dataare reported for [Fe,(CO),(p-SnR',)] and [Fe2(CO),(p-SnR2,)]. Mossbauer data are also presented forcompounds 1-3, and interpreted in terms of the structural data for these and other systems.We have recently reported on a series of cluster speciesderived from divalent tin,'., and also on the use of suchreagents in the synthesis of mixed heterometallic clustersystems ' which can have core nuclearities of up to ten metalatoms.With ruthenium and osmium dodecacarbonyls we haveshown that cluster expansion can occur with organo-tin(r1)or -lead(u)' reagents, as is also the case for tetrairidiumdodecacarbonyl.' Nuclearities of Ru,Sn,, Ru,Sn,, Os,Sn,,Ir4Sn and Ir4Sn, and many others have been characterised.Initially these results were obtained with the tin(r1) dialkyl SnR,[R = CH(SiMe,),,], but more recently a variety of other tin(r1)species has become available. We now report on the reactions ofthe iron carbonyl [Fe,(CO), ,] with diaryltin(I1) compounds andwith M[CH(PPh,),], (M = Sn or Pb).The diaryltin speciesSnR, (R = 2,4,6-triisopropylphenyl, R2 = 2,6-diethylphenyl)are accessible from tin(Ir) chloride and the appropriate lithiumreagent.' These species exist in solution as oligomers, buthave been shown to be the sources of SnR, units in clustersynthesis." The species M[CH(PPh,),], (M = Sn or Pb) aremonomers with three-co-ordinate tin atoms, and have P,Cligation at the metal atom (see below). The Mossbauer spectraof heterometallic clusters with two or more active nucleihave previously been studied, and shown to provide usefulinformation on the bonding in such molecules when used inconjunction with crystallographic data.' ' In the presentwork, both tin and iron were available as probes, and spectrafor both are reported.Results and Discussion(a) Synthesis of iron-tin clustersBis(2,4,6-triisopropylphenyl)tin(11) has been shown to exist insolution as a trimer." However, on warming or irradiation,solutions of this orange material turn deep red.Such solutionshave reactivity towards clusters paralleling that of bis[bis(tri-methylsilyl)methyl]tin(~~) ,*' (also deep red), known fromcryoscopic and other measurements l 9 s 2 O to exist as a mixtureof monomers and dimers in solution. On refluxing a mixtureof (SnR',), and [Fe,(CO),,] in hexane the deep green of theiron compound is slowly discharged, and orange crystals of[Fe,(CO),(p-SnR',)] 1 may be isolated after chromatography.The reaction also affords a blue species, but this decomposes onthe silica column.By contrast, if the diaryltin reagent is usedimmediately after synthesis (at ca. -80 "C) as the deep redsolution prior to trirneri~ation,'~ there is no reaction with thedodecacarbonyl, as is also the case for the dialkyltin

展开