Pheromones may not be the best solution although they may help. I was a scout at one point and there were at least 2 of those kids in my troop. Unfortunatley they seemed to have poor home lives, and eventualy turned into criminals with age. One robbed an old lady for pills.
You may need to try being his friend instead of leader. Try to rub off on him, and attempt to boost his own self worth. He may just need to have a positive role model that isn’t authoritarian.
Many people with such dispositions seem to be angry with society, and feel that they are an exile. Letting him know that at least you value him could prove very effective in positively affecting his attitude, and maybe the outcome of his life. Who knows, after time he may come to enjoy the scout meeting and want to be more involved as well as interested in bettering himself and the people around him.