Jc. Kim et al., SYNTHESIS AND ROTATIONAL BARRIER OF TUNGSTEN(II) PORPHYRIN DIMER, [W(TPP)](2) (TPP=TETRAPHENYLPORPHYRIN), Polyhedron, 15(1), 1996, pp. 57-62
Dimeric tungsten porphyrin, [W(TPP)](2)(TPP = tetraphenylporphyrin dia
nion), has been prepared from the reaction between TPPH2 and W(CO)(6)
in refluxing decalin and the rotational barrier about the tungsten-tun
gsten quadruple bonds examined by variable-temperature H-1 NMR of the
beta-pyrrole resonances. The barrier energy obtained by lineshape anal
ysis was 11.3 kcal mol(-1). As a measure of relative delta-bond streng
th, this result indicates the delta-bond in tungsten porphyrin dimer i
s stronger than that of the molybdenum analogue (6.3 kcal mol(-1)) in
an isostructural porphyrin system. [W(TPP)](2) has shown reactivities
toward p-tolyl azide and hydrogen peroxide to afford N=W(TPP) and W(O)
(O-2)(TPP), respectively.