Ruthenium Complexes with Chiral Tetradentate Imino−Sulfoxide Ligands

Treatment of 2-(methylsulfinyl)benzaldehyde (1) with ethylenediamine or (1R,2R)-(−)-1,2-diaminocyclohexane afforded
N,N‘-bis[2-(methylsulfinyl)benzylidene]ethylenediamine (L1) or (1R,2R)-N,N‘-bis[2-(methylsulfinyl)benzylidene]-1,2-cyclohexanedia mine (L2), respectively. Lithiation of 2-bromobenzaldehyde diethylacetal with n-BuLi/TMEDA followed
by reaction with (1R,2S,5R)-(−)-menthyl-(S)-p-toluenesulfinate afforded 2-(S)-(p-tolylsulfinyl)benzaldehyde diethyl
acetal (2). Deprotection of 2 with pyridinium tosylate followed by condensation with ethylenediamine, (1R,2R)-(−)-diaminocyclohexane, or (S,S)-(+)-diaminocyclohexane afforded N,N‘-bis[2-(S)-(p-tolylsulfinyl)benzylidene]ethylenediamine (L3), (1R,2R)-N,N‘-bis[2-(S)-(p-tolylsulfinyl)benzylidene]-1,2-cyclohexanediamine ((R,R)-L4), or (S,S)-N,N‘-bis[2-(S)-(p-tolylsulfinyl)benzylidene]-1,2-cyclohexanediamine ((S,S)-L4), respectively. Treatment of [Ru(PPh3)3Cl2]
with L afforded trans-[Ru(L)Cl2] [L = L1 (3), L2 (4), L3 (5), (R,R)-L4 ((R,R)-6), (S,S)-L4 ((S,S)-6)]. The X-ray structures
of (SS,RS)-4, (R,R)-6, and (S,S)-6 have been determined. The average Ru−N, Ru−S, and Ru−Cl distances in
(SS,RS)-4 are 2.063, 2.2301, and 2.4039 Å, respectively. The corresponding distances in (R,R)-6 are 2.071, 2.256,
and 2.411 Å, and those in (S,S)-6, 2.058, 2.2275, and 2.3831 Å. Compound 3 exhibited a reversible Ru(III/II)
couple at 0.56 V vs Cp2Fe+/0 in CH2Cl2. Treatment of 3 with AgNO3 in water afforded the aqua compound trans-[Ru(L1)Cl(H2O)][PF6] (7), which has been characterized by X-ray crystallography. The Ru−Cl, Ru−O, average
Ru−N, and average Ru−S distances in 7 are 2.3733(6), 2.1469(16), 2.071, and 2.2442 Å, respectively. Treatment
of 3 with AgNO3 followed by reaction with PPh3 afforded [Ru(L1)(PPh3)2][PF6]2 (8). Treatment of [Os(PPh3)3Cl2] with
L1 resulted in deoxygenation of one sulfoxide group of L1 and formation of [Os(L5)Cl2(PPh3)] (9) (L5 = N-[2-(methylsulfinyl)benzylidene]-N‘-[2-(methylthio)benzylididene]ethylenediamine), which has been characterized by X-ray
crystallography. The average Os−S(O), Os−N(trans to P), Os−N(trans to S), Os−P, and Os−Cl distances are
2.1931, 2.085, 2.175, 2.3641, and 2.4266 Å, respectively.