Accurate global ab initio surfaces are presented for the title reactions and competing exchange processes. The ab initio calculations were based on the quadratic configuration interaction treatment with all single and double excitations and perturbative account for triple excitations together with a 6-311++G(3df,2pd) basis, the multi-reference configuration interaction method with the Davidson correction procedure together with an aug-cc-pVTZ basis, and the unrestricted coupled-cluster treatment with all single and double excitations and perturbative account for triple excitations together with an aug-cc-pVQZ basis. The surfaces are interpolations of ab initio data for energies, energy gradients, and second derivatives at configurations scattered throughout the relevant configuration space.