Preheat oven to 350.. Mix chocolate, pecans, 2/3 cup of the sugar and the cinnamon; set aside. Mix flour, baking soda, baking powder and salt; set aside.
Beat butter and remaining 1 1/3 cups sugar in large bowl with electric mixer on medium speed until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Blend in vanilla. Add flour mixture alternately with the sour cream, beating after each addition until well blended. Spoon half of the batter into greased 13x9 inch baking pan; top with half of the chocolate mixture. Repeat layers.
Bake 40 to 45 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack. Cut into squares and serve.