Cooperative B–H Activation: Ligand Diversity in Groups 6 and 8 Transition Metal κ2-N,E-Chelated Complexes (E = S or Se)

The synthesis, structure, and reactivity of the N-heterocyclic carbene (NHC) -supported κ2-N, S-chelated ruthenium complex (IMe) (PPh3) Ruκ2-N, S- (mbz) 2 (IMe = 1, 3-dimethylimidazol-2-ylidene, mbz = 2-mercaptobenzothiazolyl (NC7H4S2) ), 2 has been established. Complex 2 is generated from the reaction of Ru (PPh3) 2Cl2, 1 with IMe followed by the addition of (mbz) K. The room-temperature reaction of 2 with BH3·THF led to the formation of the dihydridoborate complex, (Ph3P) Ruκ3-H, S, S′- (NH2BSBH2N) (S2C7H4) 2, 3. Further, the synthesis and structure of Cp*-supported κ2-N, S-chelated tungsten complexes, Cp*W (CO) 2κ2-N, S- (NC7H4S2), 5 and Cp*W (CO) 2κ2-N, S- (NC7H4S2) κ2-N, S- (N (CH3) C5H4S), 6, generated from the reaction of Cp*W (CO) 3Me, 4 and Na (H3B-NC7H4S2) have been described. In a similar fashion, pyridine-2-thiolato/selenolato ligand-supported Cp*-based κ2-N, E-chelated (E = S and Se) tungsten complexes, Cp*W (CO) 2κ2-N, E- (NC5H4E) (7a: E = S (pyridine-2-thiolato), 7b: E = Se (pyridine-2-selenolato) ), have been isolated from the reaction of Cp*W (CO) 3Me, 4 and Na (H3B-NC5H4E) ligands. The reaction of bulky borane ArFBH2 (ArF = 3, 5-bistrifluoromethylbenzyl) with 5 led to the isolation of a borate species, Cp*W (CO) 2κ2-S, H- (H2ArFB-NC7H4S2), 10. The complex Cp*Mo (CO) 2κ2-N, Se- (NC5H4Se), 9 generated from the salt elimination reaction of Cp*Mo (CO) 3Cl, 8 and K (NC5H4Se) reacts with BH3·THF to yield the borate complex Cp*Mo (CO) 2κ2-Se, H- (H3B-NC5H4Se), 11. To investigate the effect of the ligand diversities on the reactivity of all of the κ2-N, E-chelated complexes, density functional theory (DFT) -based calculations were performed.