Gas-phase chemistry of transition of metal-imido and -nitrene ion complexes. Oxidative addition of N-H bonds in NH/sub 3/ and transfer of NH from a metal center to an alkene

Journal Article · Wed Sep 28 04:00:00 EDT 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00228a002· OSTI ID:6048267

Buckner, S W; Gord, J R; Freiser, B S

The gas-phase chemistry of a number of bare transition metal-nitrene and -imido ion complexes, MNH/sup +/ are reported herein. Group 3, 4, and 5 atomic metal ions react with NH/sub 3/ at thermal energies to generate MNH/sup +/ via dehydrogenation. A reaction mechanism is proposed involving initial oxidative addition to an N-H bond, in analogy to mechanisms proposed for reactions of gaseous atomic metal ions with hydrocarbons. Cr/sup +/ reacts with NH/sub 3/ via slow condensation to form CrNH/sub 3//sup +/, as do all group 6-11 atomic metal ions investigated. However, excited-state Cr/sup +/ reacts with NH/sub 3/ via bond-insertion reactions to form CrNH/sub 2//sup +/ and CrNH/sup +/. An unidentified metastable electronic state of Cr/sup +/, produced by direct laser desorption of chromium foil, reacts with much higher efficiency than does kinetically excited Cr/sup +/. FeO/sup +/ reacts with NH/sub 3/ to generate FeNH/sup +/ with loss of H/sub 2/O. Thermochemical studies of VNH/sup +/ and FeNH/sup +/ involving ion-molecule reactions indicate values of D/degree/(V/sup +/-NH) = 101 /plus minus/ 7 kcal/mol and D/degree/(Fe/sup +/-NH) = 54 /plus minus/ 14 kcal/mol, the latter value in accord with D/degree/(Fe/sup +/-NH) = 61 /plus minus/ 5 kcal/mol obtained from photodissociation. The high bond strength for VNH/sup +/ indicates multiple bonding, analogous to that in the isoelectronic VO/sup +/, while the weaker bond strength for FeNH/sup +/ indicates a single bond, analogous to that in the isoelectronic FeO/sup +/. Proton-transfer experiments indicate PA(VN) = 220 /plus minus/ 4 kcal/mol from which /delta/H/sub f/(VN) = 111 /plus minus/ 9 kcal/mol and D/degree/(V-N) = 125 /plus minus/ 9 kcal/mol are obtained. VNH/sup +/ is unreactive with ethene and benzene, but FeNH/sup +/ transfers NH to ethene and benzene through metathesis and homologation reactions. 41 references, 2 figures, 2 tables.

• Research Organization: Purdue Univ., West Lafayette, IN (USA)
• DOE Contract Number: FG02-87ER13766
• OSTI ID: 6048267
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:20; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHEMICAL REACTIONS
COMPLEXES
DATA
EXPERIMENTAL DATA
FLUIDS
GASES
INFORMATION
NITROGEN COMPOUNDS
NUMERICAL DATA
TRANSITION ELEMENT COMPLEXES