The Versatile Coordination Modes of Monophosphine‐ o ‐Carborane in the Formation of Iridium and Rhodium Complexes: Synthesis, Reactivity, and Characterization

Monophosphine‐ o ‐carborane has four competitive coordination modes when it coordinates to metal centers. To explore the structural transitions driven by these competitive coordination modes, a series of monophosphine‐ o ‐carborane Ir,Rh complexes were synthesized and characterized. [Cp*M(Cl) 2 {1‐(PPh 2 )‐1,2‐C 2 B 10 H 11 }] (M=Ir ( 1 a ), Rh ( 1 b ); Cp*=η 5 ‐C 5 Me 5 ), [Cp*Ir(H){7‐(PPh 2 )‐7,8‐C 2 B 9 H 11 }] ( 2 a ), and [1‐(PPh 2 )‐3‐(η 5 ‐Cp*)‐3,1,2‐MC 2 B 9 H 10 ] (M=Ir ( 3 a ), Rh ( 3 b )) can be all prepared directly by the reaction of 1‐(PPh 2 )‐1,2‐C 2 B 10 H 11 with dimeric complexes [(Cp*MCl 2 ) 2 ] (M=Ir, Rh) under different conditions. Compound 3 b was treated with AgOTf (OTf=CF 3 SO 3 − ) to afford the tetranuclear metallacarborane [Ag 2 (thf) 2 (OTf) 2 {1‐(PPh 2 )‐3‐(η 5 ‐Cp*)‐3,1,2‐RhC 2 B 9 H 10 } 2 ] ( 4 b ). The arylphosphine group in 3 a and 3 b was functionalized by elemental sulfur (1 equiv) in the presence of Et 3 N to afford [1‐{(S)PPh 2 }‐3‐(η 5 ‐Cp*)‐3,1,2‐MC 2 B 9 H 10 ] (M=Ir ( 5 a ), Rh ( 5 b )). Additionally, the 1‐(PPh 2 )‐1,2‐C 2 B 10 H 11 ligand was functionalized by elemental sulfur (2 equiv) and then treated with [(Cp*IrCl 2 ) 2 ], thus resulting in two 16‐electron complexes [Cp*Ir(7‐{(S)PPh 2 }‐8‐S‐7,8‐C 2 B 9 H 9 )] ( 6 a ) and [Cp*Ir(7‐{(S)PPh 2 }‐8‐S‐9‐OCH 3 ‐7,8‐C 2 B 9 H 9 )] ( 7 a ). Compound 6 a further reacted with n BuPPh 2 , thereby leading to 18‐electron complex [Cp*Ir( n BuPPh 2 )(7‐{(S)PPh 2 }‐8‐S‐7,8‐C 2 B 9 H 10 )] ( 8 a ). The influences of other factors on structural transitions or the formation of targeted compounds, including reaction temperature and solvent, were also explored.