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Fast‐atom Bombardment (FAB) Mass Spectra of Nitrile or Cyanamide Complexes with the {M(Ph 2 PCH 2 CH 2 PPh 2 ) 2 } n + (M=Fe or Re) Metal Sites. Application to Reactions Induced under FAB Conditions
Author(s) -
Martins Luísa M. D. R. S.,
Guedes da Silva M. Fátima C.,
Marques Indalécio,
Fraústo da Silva Joäo J. R.,
Vaz M. Cândida N.,
Pombeiro Armando J. L.
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19960315)10:4<447::aid-rcm490>3.0.co;2-n
Subject(s) - chemistry , cyanamide , ligand (biochemistry) , medicinal chemistry , metal , fast atom bombardment , fragmentation (computing) , polyatomic ion , dehydrogenation , rhenium , mass spectrum , nitrile , photochemistry , ion , inorganic chemistry , catalysis , organic chemistry , biochemistry , receptor , computer science , operating system
The fast‐atom bombardment (FAB) mass spectra, in 3‐nitrobenzyl alcohol (NOBA) matrices, of the cyanamide or organonitrile complexes trans ‐[FeH(NCR)(dppe) 2 ][BF 4 ] [1; R=NH 2 , NMe 2 , NEt 2 or NC(NH 2 ) 2 ; dppe=Ph 2 PCH 2 CH 2 PPh 2 ] and cis ‐ or trans ‐[ReCl(NCR)(dppe) 2 ] (2; R=aryl), which have a diphosphinic {M(dppe) 2 } n + metal centre, are presented and discussed. Molecular ions have been detected for 1, [R=NH 2 or NC(NH 2 ) 2 ], and only for the trans isomers of 2 in agreement with the higher stability of their oxidized forms in comparison with those of the cis compounds. Possible fragmentation patterns are proposed, involving the stepwise elimination of ligands from the metal (NCR, H and dppe for 1; Cl, NCR and dppe for 2), preceding (for 1) the fragmentation of the diphosphine ligand which, nevertheless, for complexes 2, can also occur in the presence of the chloride ligand. This is interpreted on the basis of the relative electron donor ability of the ligands. Different fragmentation modes are observed for the dppe ligand, involving, e.g., dehydrogenation and loss of C 2 H 4 , Ph · , PPh or P · , in processes involving reductive or oxidative elimination steps. Rhenium fragment ions are more susceptible to oxygenation than the iron ones, in accord with the greater tendency of the former metal to reach higher oxidation states. The identification of reactions induced and monitored by FAB‐MS was also essayed and although trans ‐[FeHCl(dppe) 2 ] (3) the starting material for the synthesis of complexes (1) and NCNMe 2 do not react per se in solution, we have detected their reaction under FAB conditions, the spectra being interpreted by considering the addition of the substrate to fragment ions generated in situ from 3; a comparison with the solution chemistry is discussed and suggestions for its further development, towards lower metal oxidation state complexes, are presented on the basis of the FAB‐MS reactions detected.