Synthetic, Spectral, Structural, and Catalytic Aspects of Some Piano‐Stool Complexes Containing 2‐(2‐Diphenylphosphanylethyl)pyridine

Reactions of the complexes [(η 5 ‐C 5 H 5 )Ru(PPh 3 ) 2 Cl], [{(η 6 ‐arene)Ru(μ‐Cl)Cl} 2 ] (η 6 ‐arene = C 6 H 6 , C 10 H 14 , and C 6 Me 6 ) and [{(η 5 ‐C 5 Me 5 )M(μ‐Cl)Cl} 2 ] (M = Rh, Ir) with 2‐(2‐diphenylphosphanylethyl)pyridine (PPh 2 Etpy) were investigated. Neutral κ 1 ‐ P ‐bonded complexes [(η 5 ‐C 5 H 5 )Ru(κ 1 ‐ P ‐PPh 2 EtPy)(PPh 3 )Cl] ( 1 ) and [(η 6 ‐arene)Ru(κ 1 ‐ P ‐PPh 2 EtPy)Cl 2 ] [arene = C 6 H 6 , ( 2 ). C 10 H 14 , ( 3 ), and C 6 Me 6 , ( 4 )] were isolated from the reactions of [(η 5 ‐C 5 H 5 )Ru(PPh 3 ) 2 Cl] and [{(η 6 ‐arene)Ru(μ‐Cl)Cl} 2 ] with PPh 2 EtPy. Treatment of 1 – 4 with NH 4 BF 4 /NH 4 PF 6 in methanol allows the synthesis of cationic κ 2 ‐ P,N ‐chelated complexes [(η 5 ‐C 5 H 5 )Ru(κ 2 ‐ P,N ‐PPh 2 EtPy)(PPh 3 )] + ( 5 ) and [(η 6 ‐arene)Ru(κ 2 ‐ P ‐ N ‐PPh 2 EtPy)Cl] + [arene = C 6 H 6 , ( 6 ), C 6 H 14 , ( 7 ), and C 6 Me 6 ( 8 )]. On the other hand, the dimers [{(η 5 ‐C 5 Me 5 )M(μ‐Cl)Cl} 2 ] (M = Rh or Ir) reacted with PPh 2 EtPy in methanol to afford cationic κ 2 ‐ P,N ‐chelated complexes [(η 5 ‐C 5 Me 5 )M(κ 2 ‐ P ‐ N ‐PPh 2 EtPy)Cl] + [M = Rh, ( 9 ); Ir, ( 10 )]. Complex 10 reacted with an excess amount of sodium azide or sodium chloride to afford the complexes [(η 5 ‐C 5 Me 5 )Ir(κ 1 ‐ P ‐PPh 2 EtPy)X 2 ] (X = N 3 – 11 ; Cl – , 12 ), establishing the hemilabile nature of the coordinated PPh 2 EtPy. The complexes were characterized by elemental analyses and various physicochemical techniques. The molecular structures of 1 , 5 , 6 , 9 , and 10 were determined crystallographically, and the catalytic potentials of 1 – 10 were evaluated towards transfer‐hydrogenation reactions under aqueous conditions.