Synthesis and Reactions of Coordinatively Unsaturated Half-Sandwich Rhodium and Iridium Complexes Having a 2,6-Dimesitylbenzenethiolate Ligand

Coordinatively unsaturated rhodium and iridium complexes bearing a bulky thiolate ligand, [Cp*M(SDmp)](BArF 4) (2a, M = Rh; 2b, M = Ir; Cp* = η5-C5Me5; Dmp = 2,6-(mesityl)2C6H3; ArF = 3,5-(CF3)2C6H3) were synthesized from the reactions of [Cp*MCl]2(μ-Cl)2 with LiSDmp and NaBArF 4. The metal centers in 2a and 2b weakly interact with the ipso-carbon of one of the mesityl groups in the SDmp ligand, while the ipso-carbon dissociates from the coordination sphere in the reactions with donor ligands. Treatment of 2a or 2b with 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) led to the formation of [Cp*M(SDmp)(bpy)](BArF 4) (3a, M = Rh; 3b, M = Ir) or [Cp*M(SDmp)(phen)](BArF 4) (4a, M = Rh; 4b, M = Ir), respectively. The reactions of 2a and 2b with 2 equiv of tert-butylisocianide or 1 atm of CO gave rise to the bis-adducts [Cp*M(SDmp)(L)2](BArF 4) (5a, M = Rh, L = CN t Bu; 5b, M = Ir, L = CN t Bu; 6a, M = Rh, L = CO; 6b, M = Ir, L = CO). The coupling of terminal alkynes and SDmp took place upon the addition of excess 1-pentyne or phenylacetylene to solutions of 2a or 2b, affording cationic complexes with an S-arylated thiophene group, [Cp*M(η4-2, 4-R2C4H2S-Dmp)](BArF 4) (7a, M = Rh, R = n Pr; 7b, M = Ir, R = n Pr; 7c, M = Rh, R = Ph; 7d, M = Ir, R = Ph).