Neutral baryonic systems with strangeness

We review the status as regards the existence of three- and four-body bound states made of neutrons and $\mathrm{\Lambda }$ hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the $\mathrm{\Lambda }nn$ system has no bound states. $\mathrm{\Lambda }\mathrm{\Lambda }nn$ strong stable states are not favored by our current knowledge of the strangeness $-1$ and $-2$ baryon-baryon interactions. However, a possible ${\mathrm{\Xi }}^{-}t$ quasibound state decaying to $\mathrm{\Lambda }\mathrm{\Lambda }nn$ might exist in nature. Similarly, there is a broad agreement about the nonexistence of $\mathrm{\Lambda }\mathrm{\Lambda }n$ bound states. However, the coupling to $\mathrm{\Xi }NN$ states opens the door to a resonance above the $\mathrm{\Lambda }\mathrm{\Lambda }n$ threshold.