Chiral Ruthenium–Sulfene Complexes – Synthesis and C–C Coupling Reactions

Abstract

Reaction of the chiral racemic complex [CpRu(mppe)(SO2)]PF6 (1, mppe = Me2PC2H4PPh2) with diazomethane or ‐ethane gave the sulfene complexes [CpRu(mppe)(RHC/SO2)]PF6 (R = H, 2a; R = Me, 2b). Treatment of 2a with prochiral enamines or deprotonated β‐oxo esters yielded C–C coupling products with 32–60% de. An analog of 2a, [NmcpRu(mppe)(H2C/SO2)]PF6 (8, Nmcp = neomenthylcyclopentadienyl) was prepared in a four‐step synthesis starting from LiNmcp and [RuCl2(PPh3)3]. Repeated crystallization of the intermediate [NmcpRu(mppe)Cl] (6) provided diastereomerically pure 6′ which added methylene stereospecifically to give diastereomerically pure 8′. Compound 8 turned out to be much less reactive towards nucleophiles than 2a, but still added deprotonated ethyl 2‐methyl‐3‐oxobutanoate with 44% de. The chiral, enantiomerically pure sulfur dioxide complex [CpRu(chir)(SO2)]PF6 [10, chir = (S,S)‐Ph2PCHMeCHMePPh2] was synthesized from [CpRu(chir)Cl] and SO2 and was characterized by X‐ray crystallography. Reaction of 10 with diazomethane gave the enantiomerically pure sulfene complex [CpRu(chir)(H2C/SO2)]PF6 (11). Addition reactions of 11 with N‐(1‐cyclopentenyl)morpholine, as well as with various enolates derived from β‐oxo esters or 1,3‐diesters proceeded with high yields and 20–90% de. The structure of a diastereomerically pure addition product, [CpRu(chir)(SO2CH2C(Me){C(O)Me}{C(O)OtBu}] (13d′), was determined crystallographically and was shown to have (R) configuration at the quaternary carbon atom. After alkylation of one of the S/O functions, the sulfinate ligand was cleaved from the metal center by ligand substitution with acetonitrile, and the resulting acetonitrile complex 15 was converted back into 10 by treatment with SO2.

Transition metal complexes bearing a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionate ligand: one methyl more matters

“…Usually these values are in a range of 1254 to 1296 cm -1 and 1096 to 1128 cm -1 respectively. [28][29][30][31][32][33][34] The result of a single crystal structure analysis of complex 11 is depicted in Fig. 8.…”

“…Once again, the asymmetrical and symmetrical SO 2 vibrations at ñ = 1291 and 1125 cm -1 are in good agreement with those reported for similar complexes. [28][29][30][31][32][33][34] Attempts to obtain single crystals suitable for X-ray structure analysis have not been successful so far.…”

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“…The further reactivity of this with enamines and b-oxoesters was studied, as were other complexes with additional chiral substituents on the Cp or diphosphine ligands. 62 [Ru(CNCH 2 )ClH(PCy 3 ) 2 ] reacts with HBF 4 •OEt 2 to give the first Ru carbyne complex, [Ru(CMe)ClH(OEt 2 )(PCy 3 ) 2 ] + . 63 A tridentate ligand C 5 H 4 CH 2 CMe(CH 2 PPh 2 ) 2 (L), incorporating both phosphine and cyclopentadienyl functions, forms [RuLCl] in which the normal configurational inversion of [M(Cp)LLA] complexes is suppressed.…”

“…ion has been shown by Rietveld analysis of the structures of BaSrPdF 6 and PbPdF 6 to contain a mixture of square planar [PdF 4 ]22 and square antiprismatic [PdF 8 ]62 160. During a study of the synthesis and structure of cis-[Pd(S 2 CNEt 2 ) 2 Br 2 ], a material of composition Pd 3 (S 2 CNEt 2 ) 4 Br 2 was prepared and found to comprise a {Pd(S 2 CNEt 2 ) 2 } moiety linked to two {Pd(S 2 CNEt 2 )Br} units through S atoms 161.…”

Synthesis of Halfsandwich Ruthenium Complexes of Sulfinic Acid Esters [1]

“…13 was identified by its known spectroscopic properties [28]. It should be mentioned that we have recently reported such a demetalation procedure and suggested a cycle to efficiently recover the quite pre cious ruthenium starting materials [1,14]. …”