In a large bowl, mix together the pineapple juice, ketchup, soy sauce
, ginger and garlic. Reserve 1/4 cup of the marinade for basting. Pour the remaining marinade into a resealable plastic bag and add the chicken. Seal the bag and toss around to distribute the marinade
. Marinate the chicken in the refrigerator for at least 4 hours or up to overnight.
Preheat the grill to medium-high heat.
Grill the pineapple 3 to 4 minutes per side, then keep warm.
Remove the chicken from the marinade and pat dry. Sprinkle the chicken with salt and pepper, and then grill until cooked through, 5 to 6 minutes per side, basting with the reserved marinade every 2 minutes. Serve the chicken with the pineapple slices.