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We present results from an analysis of bimodal clusters observed with the ROSAT PSPC. The isothermal temperatures are poorly constrained but are roughly, 2 - 4 keV, consistent with that expected from the luminosity-temperature relationship for rich clusters extrapolated to the bimodal cluster luminosities. These are the first temperatures measured for subclusters in bimodal systems. The isothermal masses, $\simeq$ 4$\times10^{14}$ ${M_\odot}$, are much smaller than those derived from rich evolved clusters and are roughly equal in a pair. Comparison to simulations of cluster formation indicates that they are the final stage before a rich cluster is formed by merger. Preliminiary analysis shows that the cooling times appear to be long compared to the age of the clusters, implying that the subclusters do not have cooling flows. The gas density profile is used together with the temperature profile to make the first measurements of the gas baryon fraction for this class of objects. We find that the average gas baryon fraction has a lower limit of $\simeq$25\%, consistent with that found for rich clusters of galaxies.
