  Transition-metal dichalcogenides open novel opportunities for the exploration
of exciting new physics and devices. As a representative system, 2H-MoS$_2$ has
been extensively investigated owing to its unique band structure with a large
band gap, degenerate valleys and non-zero Berry curvature. However,
experimental studies of metastable 1T polytypes have been a challenge for a
long time, and electronic properties are obscure due to the inaccessibility of
single phase without the coexistence of 1T', 1T'' and 1T''' lattice structures,
which hinder the broad applications of MoS$_2$ in future nanodevices and
optoelectronic devices. Using ${K_x(H_2O)_yMoS_2}$ as the precursor, we have
successfully obtained high-quality layered crystals of the metastable
1T'''-MoS$_2$ with $\sqrt{3}a\times\sqrt{3}a$ superstructure and metastable
1T'-MoS$_2$ with a$\times$2a superstructure, as evidenced by structural
characterizations through scanning tunneling microscopy, Raman spectroscopy and
X-ray diffraction. It is found that the metastable 1T'-MoS$_2$ is a
superconductor with onset transition temperature (${T_c}$) of 4.2 K, while the
metastable 1 T'''-MoS$_2$ shows either superconductivity with Tc of 5.3 K or
insulating behavior, which strongly depends on the synthesis procedure. Both of
the metastable polytypes of MoS$_2$ crystals can be transformed to the stable
2H phase with mild annealing at about 70 $^{\circ}$C in He atmosphere. These
findings provide pivotal information on the atomic configurations and physical
properties of 1T polytypes of MoS$_2$.
