Statement I: PF₃ is weakest donor as well as weakest acceptor compared to PMe₃ in synergic bonding

Statement II: Me group is having +I effect while F atom is having –I effect.

Statement I is false but Statement II is correct

The answer is (4) Statement I is false but Statement II is correct.

Statement I is false because PF₃ is a weaker donor but not a weaker acceptor than PMe₃ in synergic bonding. This is because the fluorine atom is more electronegative than the methyl group, so it pulls electrons away from the phosphorus atom more strongly. This makes the phosphorus atom less electron-rich, which makes it a weaker donor. However, the fluorine atom also has a smaller atomic radius than the methyl group, so it overlaps better with the phosphorus atom's orbitals, which makes it a stronger acceptor.

Statement II is correct because the methyl group has a +I effect, which means that it donates electrons to the phosphorus atom. The fluorine atom has a –I effect, which means that it withdraws electrons from the phosphorus atom. The +I effect of the methyl group is stronger than the –I effect of the fluorine atom, so the overall effect of PMe₃ is to make the phosphorus atom more electron-rich. This makes PMe₃ a stronger donor than PF₃.