Preheat oven to 350°. Grease and flour a 12-cup Bundt pan.
Stir pecans, butter, and sugar together with a fork. Sprinkle mixture in bottom of prepared pan.
Whisk together flour, baking soda, and salt. Set aside.
Using an electric mixer on medium speed, beat butter, brown sugar, granulated sugar, and vanilla until fluffy (3-5 minutes). Add eggs, one at a time, beating just until blended after each addition.
Add flour mixture, alternating with buttermilk. Begin and end with flour mixture. Reduce mixer speed to low and beat just until blended. Mix in chocolate chips. Transfer batter to prepared pan.
Bake 50-55 minutes, or until a cake tester inserted into the center comes out clean.
Cool in pan on wire rack for 10 minutes. Remove from pan to cool completely on wire rack.