Electron deficient compounds are those where the central atom has less than 8 e– s in its outermost shell.
Out of BCl3 and SiCl4, the former is an electron deficient compound since it has only 6 electrons in the outermost shell.
SiCl4 is not an electron deficient compound.
However, it can accept electrons by expanding its octet due to presence of empty d-orbitals. Thus, it may form species like SiF62–.