MO scheme for coordination complexes (tetrahedral) - Heteroligand vs. homoligand
Bis(triphenylphosphine)nickel chloride can have be tetrahedral or square planar depending on conditions. In any case the SALCs for a tetrahedral complex with heteroligands will depend on the point group of the complex. For [NiCl2(PPh3)2], the point gorup is C2v and not Td like for same ligand tetrahedral. You need to check the character tables