useing Organge Marmalaid for pecan coating
Jam (or jelly) might be able to be cooked down into a candy, but, that's beside the point, as jam is sugar based. Unless you were thinking of using sugar free jam... which would make it an interesting question.
A sugar free jam could probably be cooked down into a coating for pecans, but... by the time you cook that much moisture away, I'm guessing the orange in it would probably start to brown. Any fruit in jam would either brown or end up being tasteless from the heat involved in making candy (300+ deg.).
If you want a sugar free coating for pecans, you'll need to turn to textural sugar subs. This list includes:
Some diabetics are okay with agave nectar, which is predominantly fructose, but from the research I've done, fructose isn't any healthier than sugar. If the person you're making these for is okay with agave nectar, though, that could be used. With all of these sweeteners, you'll have to get the go ahead from the person you're making them for, as they are all potentially laxating in large amounts.
Btw, this vetting process doesn't just apply to sugar subs, it applies to a host of ingredients. There is no single approach to diabetic nutrition. Approaches include:
everything in moderation
anything goes with appropriate medication
a combination of the above
For all you know, the person you're making these for may be eating low fat and can't eat pecans. Do your homework. Baking for people with diabetes is an honorable quest, but it comes with responsibilities. If the detective work is too much of a hassle for you, get them a non food gift.
Assuming they can handle one or all of these sugar subs, pralines are not that difficult. If your goal is an orange flavored pecan coating, I would utilize a two step process
1. Dip the pecans in a very thick sugar substitute based caramel syrup
2. Dip the still warm pecans in a powdered sugar sub/orange zest/spice (if using) mixture.
That would give you an orange spiced praline. Polyd works very well for the caramel coating and isomalt is ideal for the powdered sugar.
Or get them something non food :)