The reaction of Re(NC6H4R)Cl-3(PPh3)(2) (R = H, 4-Cl, 4-OMe) with 1,2-bis(d
iphenylphosphino)ethane (dppe) is investigated in refluxing ethanol. The re
action produces two major products, Re(NC6H4R)Cl(dppe)(2)(2+) (R = H, 1-H;
R = Cl, 1-Cl; R = OMe, 1-OMe) and the rhenium(III) species Re(NHC6H4R)Cl(dp
pe)(2)(2+) (R = H, 2-H; R Cl, 2-Cl). Complexes 1-H (orthorhombic, Pcab, a =
22.3075(10) Angstrom, b = 23.1271(10) Angstrom, c = 23.3584(10) Angstrom,
Z = 8), 1-Cl (triclinic, P (1) over bar, a = 11.9403(6) Angstrom, b = 14.66
73(8) Angstrom, c = 17.2664(9) Angstrom, alpha = 92.019(1)degrees, beta = 9
7.379(1)degrees, gamma = 90.134(1)degrees, Z = 2), and 1-OMe (triclinic, P1
, a = 11.340(3) Angstrom, b = 13.134(4) Angstrom, c = 13.3796(25) Angstrom,
alpha = 102.370(20)degrees, beta = 107.688(17)degrees, gamma = 114.408(20)
degrees, Z = 1) are crystallographically characterized and show an average
Re-N bond length (1.71 A) typical of imidorhenium(V) complexes. There is a
small systematic decrease in the Re-N bond length on going from Cl to H to
OMe. Complex 2-Cl (monoclinic, Cc, a = 24.2381(11) Angstrom, b = 13.4504(6)
Angstrom, c = 17.466(8) Angstrom, beta = 97.06900(0)degrees, Z = 4) is als
o crystallographically characterized and shows a Re-N bond length (1.98 Ang
strom) suggestive of amidorhenium(III). The rhenium(III) complexes exhibit
unusual proton NMR spectra where all of the resonances are found at expecte
d locations except those for the amido protons, which are at 37.8 ppm for 2
-Cl and 37.3 ppm for 1-H. The phosphorus resonances are also unremarkable,
but the C-13 spectrum of 2-Cl shows a significantly shifted resonance at 17
7.3 ppm which is assigned to the ipso carbon of the phenylamido ligand. The
extraordinary shifts of the amido hydrogen and ipso carbon are attributed
to second-order magnetism that is strongly focused along the axially compre
ssed amido axis. The reducing equivalents for the formation of the Re(III)
product are provided by oxidation of the ethanol solvent, which produces ac
etal and acetaldehyde in amounts as much as 30 equiv based on the quantity
of rhenium starting material. Equal amounts of hydrogen gas are produced, s
uggesting that the catalyzed reaction is the dehydrogenation of ethanol to
produce acetaldehyde and hydrogen gas. Metal hydrides are detected in the r
eaction solution, suggesting a mechanism involving beta -elimination of eth
anol at the metal center. Formation of the amidorhenium(III) product possib
ly arises from migration of a metal hydride in the imidorhenium(V) complex.