  Using deep Chandra and optical spectroscopic observations, we investigate an
intriguing, young massive group, RXJ1648.7+6109, at z=0.376, and we combine
these observations with previous measurements to fit the scaling relations of
intermediate-redshift groups and poor clusters. RXJ1648 appears to be in an
early stage of formation; while it follows X-ray scaling relations, its X-ray
emission is highly elongated and it lacks a central, dominant BCG. Instead,
RXJ1648 contains a central string of seven bright galaxies, which have a
smaller velocity dispersion, are on average brighter, and have less star
formation (lower EW([OII]) and EW(H_delta)) than other group galaxies. The 4-5
brightest galaxies in this string should sink to the center and merge through
dynamical friction by z=0, forming a BCG consistent with a system of RXJ1648's
mass even if 5-50% of the light is lost to an intracluster light component
(ICL). The L_X-T_X relation for intermediate-redshift groups/poor clusters is
very similar to the low-redshift cluster relation and consistent with the
low-redshift group relation. In contrast, the L_X-sigma_v and sigma_v-T_X
relations reveal that intermediate-redshift groups/poor clusters have
significantly lower velocity dispersions for their X-ray properties compared to
low-redshift systems, however the intermediate-redshift relations are currently
limited to a small range in luminosity.
