  We report the first results of relativistic correlation calculation of the
spectroscopic properties for the ground state of E112H and its cation in which
spin-orbit interaction is taken into account non-perturbatively. Studying the
properties of E112 (eka-Hg) is required for chemical identification of its
long-lived isotope, $^{283}$112. It is shown that appropriate accounting for
spin-orbit effects leads to dramatic impact on the properties of E112H whereas
they are not so important for E112H$^+$. The calculated equilibrium distance,
$R_e^{calc}=1.662$ A, in E112H is notably smaller than
$R_e^{expt}=(1.738\pm0.003)$ A and $R_e^{calc}=1.738$ A in HgH, whereas the
dissociation energy, $D_e^{calc}=0.42$ eV, in E112H is close to
$D_e^{expt}=0.46$ eV and $D_e^{calc}=0.41$ eV in HgH. These data are quite
different from $R_e^{NH}=1.829$ A and $D_e^{NH}=0.06$ eV obtained for E112H
within the scalar-relativistic Douglas-Kroll approximation [Nakajima and Hirao,
Chem. Phys. Lett., 329, 511 (2000)]. Our results indicate that E112 should not
be expected to be "more inert" than Hg in opposite to the results by other
authors.
