Synthesis, reactions and multinuclear NMR spectroscopic studies of organo bimetallic and trimetallic compounds

摘要

The 207Pb and 119Sn NMR chemical shift were used to study the effect of temperature on Ph3MClud(M= Pb and Sn) adducts in the presence of 10% excess pyridine. The 207Pb and 119Sn chemicaludshift indicate a slow exchange at low temperatures below -90 0C and a significant exchange atudhigher temperatures above 10 0C. A plot of temperature against 207Pb or 119Sn chemical shiftudshowed a curve with gentle slope at lower and a steep slope at higher temperatures. A goodudlinear correlation (coefficient. of 0.95) between Hammett substituent constant and 207Pb or 119Snudchemical shift of para-substituted derivatives of Ph3MCl.py* (py* = NMe2, OMe, Me, Ph, H, Br,udCOPh and COMe; at -90 0C in CD2Cl2/CH2Cl2) was found. Both 207Pb and 119Sn chemical shiftudranges are characteristic of five coordinate systems resolving into trigonal bipyramidal geometryudas shown by X-ray crystal structures.udNew complexes of the type [CpFe(CO)(SnPh3)L] (L = PPh3, PBu3, PCy3, PMe3, P(NMe2)3,udPMePh2, PMe2Ph, P(p-FC6H5)3, P(p-OMeC6H4)3, P(p-tolyl)3, P(OMe)3, and P(OPh)3 wereudsynthesized by ultraviolet irradiation of [CpFe(CO)2(SnPh3)] and the appropriate phosphine orudphosphite ligand. 57Fe NMR studies of the complexes showed an increasing linear relationshipudwith Tolman’s steric parameter, whereas with Tolman’s electronic parameter the 57Fe chemicaludshift showed a decrease. The X-ray crystallographic profile of the selected new piano stool typeudcomplexes shows a significant correlation to the NMR data (solution state), i.e. Fe-Sn, Fe-P bondudlength and Sn-Fe-P bond angle against chemical shifts of 207Pb and 119Sn. Disubstitutedudcomplexes of the type [CpFe(SnPh3)L2] (L = PMe3, PMe2Ph, P(OMe)3 and P(OPh)3 wereudsynthesized under similar conditions as monosubstituted compounds. The correlation trendsudbetween the NMR data and X-ray crystallographic profiles are similar to those found forudmonocarbonylated complexes.udTungsten phosphine complexes of the type [W(CO)5(PR3)] (prepared from [W(CO)6] underudthermal conditions) and [W(CO)4(NCMe)(PR3)] (prepared from [W(CO)5(PR3)] by use ofudMe3NO-promoted decarbonylation) were synthesized and characterized by, among otherudmethods X-ray diffraction techniques (R = Ph, p-tolyl, p-OMeC6H4, p-FC6H4, p-CF3C6H4, andudNMe2). The tungsten complexes [W(CO)4(NCMe)(PR3)] react with [(dppp)Pt{C≡C-C5H4N}2] atudroom temperature to form new complexes of the type [(dppe)Pt{C≡C-C5H4N-W(CO)4(PR3)}2] which were characterized unambiguously by NMR spectroscopy. There is a fair correlationudbetween 195Pt and 183W NMR chemical shifts and Tolman’s electronic parameter which indicatesuda fair influence by the substituents of the phosphorus atom on both metal centres.udTungsten complexes of the type [W(CO)4(NCMe)(L)] (L= PPh3, P(p-FC6H4)3, P(p-OMeC6H4)3,udP(p-tolyl)3, P(p-CF3C6H4)3, PMePh2, and PPh2(C6F5) react with [(PPh3)2Rh(H)2(pytca)] (pytca =ud2-(4-pyridyl)thiazole-4-carboxylate) to form new complexes of the type [(PPh3)2Rh(H)2(pytca)-udW(CO)4(L)] under mild conditions. These complexes were characterized principally by NMRudspectroscopy and X-Ray crystallography (L = P(p-tolyl)3). Crystallographic evidence was foundudfor π-π-π interactions involving two phenyl rings, one of the two phosphines bonded to rhodiumudatom, one of the three phosphines bonded to tungsten and the pyridyl ring of the thiazoleudcorboxylate group. A second π-π interaction is found between a thiazole and a phenyl ring of theudphosphine ligand bonded to the rhodium atom. A fair correlation was found between the rhodiumudand tungsten chemical shift measured from this series of complexes as a result of varied paraphenyludsubstituent of phosphine ligand bonded to the tungsten atom. This therefore implies theudpossible existence of electronic communication between the two bridged metal centres.