Stereochemically Controlled Synthesis of Ruthenium(II) Complexes Containing Bis(oxazolin-2'-yl)pyridine Ligands. X-ray Crystal Structures of trans-[RuCl(2)(PPh(3)){kappa(3)-N,N,N-(S,S)-(i)Pr-pybox}] and [RuCl(=C=C=CPh(2))(PPh(3)){kappa(3)-N,N,N-(S,S)-(i)Pr-pybox}][PF(6)] ((S,S)-(i)Pr-pybox= 2,6-Bis[4'-(S)-isopropyloxazolin-2'-yl]pyridine).
The treatment of achiral and chiral bis(oxazolin-2'-yl)pyridine (pybox) complexes trans-[RuCl(2)(eta(2)-H(2)C=CH(2))(k(3)-N,N,N-pybox)] [pybox= 2,6-bis(dihydrooxazolin-2'-yl)pyridine] (1a) and [RuCl(2)(eta(2)-H(2)C=CH(2))(k(3)-N,N,N-(SS)-(i)Pr-pybox}] [(SS)-(i)Pr-pybox= 2,6-bis[4'-(S)-isopropyloxazolin-2'-yl]pyridine] (1b) with an excess of triphenylphosphine in dichloromethane at 50 degrees C leads to the formation of the first ruthenium(II) derivatives containing both bis(oxazolin-2'-yl)pyridine and phosphine ligands trans-[RuCl(2)(PPh(3))(kappa(3)-N,N,N-pybox)] (2a) and trans-[RuCl(2)(PPh(3)){kappa(3)-N,N,N-(SS)-(i)Pr-pybox}] (2b). Chiral complex 2b slowly isomerizes in acetone at 50 degrees C to generate cis-[RuCl(2)(PPh(3)){kappa(3)-N,N,N-(SS)-(i)Pr-pybox}] (3). Complex 3 can be also obtained from the reaction of 1b with PPh(3) in MeOH. The structure of 3 has been confirmed by X-ray crystallography [orthorhombic; space group P2(1)2(1)2(1); Z = 4; a = 12.772(6) Å, b = 15.208(5) Å, c = 19.601(7) Å; final R1= 0.0565 and wR2 = 0.0944 (both for I > 2sigma(I))]. The reaction of the achiral pybox complex 2a with 1,1-diphenyl-2-propyn-1-ol and AgBF(4) in CH(2)Cl(2) stereoselectively affords the cationic allenylidene derivative [RuCl(=C=C=CPh(2))(PPh(3))(kappa(3)-N,N,N-pybox)][BF(4)] (4a), while the methoxycarbene complex [RuCl{=C(OMe)CH=CPh(2)}(PPh(3))(kappa(3)-N,N,N-pybox)][PF(6)] (5) is obtained when the reaction is conducted in methanol and in the presence of NaPF(6), via the addition of MeOH to the initially formed allenylidene complex 4a. In contrast, the chiral pybox complex 2b reacts with 1,1-diphenyl-2-propyn-1-ol and NaPF(6) in MeOH to give the stable allenylidene complex [RuCl(=C=C=CPh(2))(PPh(3)){kappa(3)-N,N,N-(SS)-(i)Pr-pybox}][PF(6)] (4b). The X-ray crystal structure of 4b [orthorhombic; space group P2(1)2(1)2(1); Z = 4; a = 14.79(3) Å, b = 16.254(8) Å, c = 22.917(18) Å; final R1 = 0.0545 and wR2 = 0.1381 (both for I > 2sigma(I))] shows an octahedral coordination of the ligands around the ruthenium atom with the chloride and triphenylphosphine ligands in a trans arrangement and mutually cis with respect to the allenylidene moiety. The allenylidene complex 4b is also formed by the reaction of the cis dichloride complex 3 with 1,1-diphenyl-2-propyn-1-ol and NaPF(6) in MeOH. IR, (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR data of all novel compounds are also reported.
Cadierno
Victorio
V
Departamento de Química Física y Analítica, Universidad de Oviedo, E-33071 Oviedo, Spain.
Gamasa
M. Pilar
MP
Gimeno
José
J
Iglesias
Luis
L
García-Granda
Santiago
S