Molybdenum-95 nuclear magnetic resonance studies on disubstituted molybdenum(0) carbonyls

Abstract

ELMER C. ALYEA and ARPAD SOMOGYVARI. Can. J. Chem. 66, 397 (1988).Molybdenum-95 nmr spectral data are reported for 40 cis-and tran~-Mo(C0)~LL' compounds and the chemical shifts discussed in relation to a simplified Ramsey expression for the paramagnetic shielding term. The identification of mixtures of products of the type Mo(CO)~-,,L,, is shown to be easily accomplished by "MO nmr spectroscopy. The "MO chemical shifts provide a sensitive probe of structural and electronic effects, as illustrated for several cyclic nitrogen ligands as well as a range of phosphine ligands in the Mo(CO)~LL' complexes. ELMER C. ALYEA et ARPAD SOMOGYVARI. Can. J. Chem. 66, 397 (1988).On a dCtermint les spectres rmn du "MO de 40 composts cis-et trans-Mo(CO),LL1 et on discute des dkplacements chimiques en fonction d'une expression de Ramsey simplifite pour le terme d'tcran paramagnttique. On dtmontre que'on peut facilement dttecter la prtsence de mClanges d'entitts du type Mo(CO)~-,,L,, en faisant appel B la rmn du "~0 . Comme on a pu le mettre en Cvidence avec plusieurs ligands azotts cycliques ainsi qu'avec un certain nombre de phosphines agissant comme ligands dans des complexes du type Mo(CO)~LL', les diplacements chimiques du "MO s'avkrent une sonde sensible pour examiner les effets de structure et tlectroniques.[Traduit par la revue]

cis-Tetracarbonylbis(triphenyl phosphite)molybdenum(0)

“…The resistance to deformation of the P--Mo--P angle may be enhanced by the shortened Mo--P bond distance, which is obviously a consequence of the greater 7r-acceptor ability of the phosphite ligand. The significantly greater shielding of the Mo nucleus in (1), as given by the tS(95Mo) value of -1754 p.p.m., relative to -1556 p.p.m, for (2) (Alyea & Somogyvari, 1988), is consistent with P(OPh)3 being a much better 7r-acceptor ligand than PPh3. (2) and (3) differ by 0.034 and 0.044 ,~, respectively.…”

95Mo NMR Studies on Cationic Phosphenium Complexes of Molybdenum

“…Although the two coupling constants were not determined accurately, both values are estimated to be in the range 220−310 Hz. Since 95 Mo NMR data have not been reported for Mo complexes possessing two different phosphorus-donating ligands, these are the first examples …”

trans-Tetracarbonylbis(tricyclohexylphosphine)molybdenum(0), trans-[Mo(CO)4(PCy3)2]

“…The title compound was synthesized by the reaction of Mo(CO)6 with PCy3 (1:2 ratio) in refluxing iso-octane for 24 h. The product was recrystallized from dichloromethaneheptane at 278 K. Relevant spectroscopic data are: u(CO) = 1870cm -I, 6(95Mo) = -1765 p.p.m., J(Mo---P) -134 Hz in CH2C12 solution (Alyea & Somogyvari, 1988).…”