A self-consistent set of thermochemical parameters for about 100 molecules in the Si-B-H-Cl system is obtained using a combination of ab initio electronic structure calculations and empirical corrections (the BAC-MP4 method). The species include stable and radical species as well as a few transition states. Trends in calculated heats of formation, bond dissociation enthalpies, and heats of reaction for various molecular decomposition channels are discussed, Silylboranes are most Likely to decompose via the elimination of I-H, HCl, or silylenes, The presence of the B atom reduces the energy required for the 1,1 elimination of H-2 from the Si atom, relative to the analogous reaction in disilane.