Prepare the chicken: Put the mangoes, cilantro, chipotles, adobo sauce, vinegar, garlic, lemon juice, canola oil, 1 tablespoon salt and 1 teaspoon pepper in a food processor and puree until smooth. Adjust the seasoning to taste.
Toss the chicken with half of the mango mixture in a resealable plastic bag and massage to coat the chicken with the sauce. Refrigerate at least 6 hours to marinate.
Put the other half of the mango mixture in a small saucepan and simmer over low heat until thick, stirring often, about 15 minutes. Season with salt. Set some of the simmered mango sauce aside for serving and use the rest for basting.
Preheat a grill to medium and brush with canola oil. Remove the chicken from the marinade, brushing off the excess marinade so it doesn't burn, and put on the grill. Grill the chicken, turning, until cooked through, about 30 minutes, basting with the simmered mango sauce during the last 5 minutes.
Meanwhile, make the chimichurri: Combine the cilantro, parsley, scallions, garlic, grapeseed oil, agave, lime juice, and salt and pepper to taste in a food processor and pulse to roughly chop. Continue processing until the sauce is finely chopped but not smooth (it shouldn't be a puree). Set aside at least 15 minutes before serving.
Transfer the chicken to a platter and serve with the chimichurri and the reserved mango sauce.