| The reactions of the dimolybdenum cage complex Mo(CO){dollar}sb4{dollar}-{dollar}rm lbracksp{lcub}i{rcub}Prsb2NPOrbracksb4Mo(CO)sb4sp{lcub}*{rcub}{dollar} with phosphorus and nitrogen nucleophiles were studied. This dimolybdenum cage complex reacted with tertiary phosphines of the type PPh{dollar}sb2{dollar}R (R = Ph, Me, H) in refluxing toluene. In each case, incorporation of a single phosphine led to the loss of three carbonyls to form orange complexes of the type {dollar}rm Mo(CO)sb3lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4Mo(CO)sb2PPhsb2R{dollar}(2, 3, 4). The X-ray molecular structure of 2 has been determined. This revealed that a cage P-O-P bond has been cleaved near the substitution site with the resulting phosphinito oxygen replacing a second CO. Additionally, the phosphido group generated displaced a third CO at the other Mo center to bridge the two metals which are now within bonding distance of each other. Under milder conditions, reactions using phosphite yielded both mono- and disubstituted products {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbracksb4Mo(CO)sb3P(OMe)sb3{dollar} or {dollar}rm Mo(CO)sb3P(OMe)sb3{dollar}-{dollar}rm lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4Mo(CO)sb3P(OMe)sb3{dollar} with the original core structure intact. Both products were mixtures of diastereomers and can be transformed to orange {dollar}rm Mo(CO)sb3lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4Mo(CO)sb2P(OMe)sb3{dollar}.; Treatment of the mixed-valent {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4Mo(CO)sb2Isb2{dollar} cage complex with sodium dimethyldithiocarbamate selectively removed the divalent molybdenum vertex to give the metalla-ligand {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4{dollar} (14) via an orange intermediate {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbracksb4{dollar}-{dollar}rm Mo(CO)sb2(Ssb2CNMesb2)sb2{dollar}. The metalla-ligand has been characterized spectrally and by X-ray crystallography. It has been used as a precursor to assemble novel heterobimetallic cage complexes of the type {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4MLsb{lcub}n{rcub}{dollar} where ML{dollar}sb{lcub}rm n{rcub}{dollar} can be {dollar}rm Cr(CO)sb4, Fe(CO)sb3, Cu(MeCN)sb2BFsb4, AgNOsb3, PtClsb2, NiBrsb2{dollar} and PdBr{dollar}sb2{dollar}, or the type {dollar}rm Mo(CO)sb3lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb5MLsb{lcub}n{rcub}{dollar} where ML{dollar}sb{lcub}rm n{rcub}{dollar} can be PdCl{dollar}sb2{dollar}, PdBr{dollar}sb2{dollar}. All these heterobimetallic cage complexes have been characterized by elemental analyses and spectral data. In addition, X-ray structures of the heterobimetallic cage complexes {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4MBr2{dollar} (M = Ni(21), Pd(25)) have been determined. Comparison of the well-resolved Al carbonyl stretching frequency and the {dollar}sp{lcub}13{rcub}{dollar}C NMR chemical shift of the cis-Mo(CO){dollar}sb4{dollar} moiety in {dollar}rm Mo(CO)sb4lbrack sp{lcub}i{rcub}Prsb2NPOrbrack sb4MLsb{lcub}n{rcub}{dollar} and also the X-ray structures of 14, 21, 25 suggest a transmission of the increasing electron demand of the second cage metal to the molybdenum vertex. ftn*See Appendix A for the structure. |
