Generation and Reactions of Ruthenium Phosphido Complexes [(η5-C5H5)Ru(PR′3)2(PR2)]: Remarkably High Phosphorus Basicities and Applications as Ligands for Palladium-Catalyzed Suzuki Cross-Coupling Reactions
✍ Scribed by José Giner Planas; Frank Hampel; J. A. Gladysz
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 277 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Reactions of [(η^5^‐C~5~H~5~)Ru(PR′~3~)~2~(Cl)] with NaBAr~F~ [BAr~F~^−^=B{3,5‐[C~6~H~3~(CF~3~)~2~]}~4~^−^; PR′~3~=PEt~3~ or 1/2Et~2~PCH~2~CH~2~PEt~2~ (depe)] and PR~2~H (R=Ph, a; __t__Bu, b; Cy, c) in C~6~H~5~F, or of related cationic Ru(N~2~) complexes with PR~2~H in C~6~H~5~F, gave the secondary phosphine complexes [(η^5^‐C~5~H~5~)Ru(PR′~3~)~2~(PR~2~H)]^+^ BAr~F~^−^ (PR′~3~=PEt~3~, 3 a–c; 1/2depe, 4 a,b) in 65–91 % yields. Additions of __t__BuOK (3 a, 4 a; [D~6~]acetone) or NaN(SiMe~3~)~2~ (3 b,c, 4 b; [D~8~]THF) gave the title complexes [(η^5^‐C~5~H~5~)Ru(PEt~3~)~2~(PR~2~)] (5 a–c) and [(η^5^‐C~5~H~5~)Ru(depe)(PR~2~)] (6 a,b) in high spectroscopic yields. These complexes were rapidly oxidized in air; with 5 a, [(η^5^‐C~5~H~5~)Ru(PEt~3~)~2~{P(O)Ph~2~}] was isolated (>99 %). The reaction of 5 a and elemental selenium yielded [(η^5^‐C~5~H~5~)Ru(PEt~3~)~2~{P(Se)Ph~2~}] (70 %); selenides from 5 c and 6 a were characterized in situ. Competitive deprotonation reactions showed that 5 a is more basic than the rhenium analog [(η^5^‐C~5~H~5~)Re(NO)(PPh~3~)(PPh~2~)], and that 6 b is more basic than P__t__Bu~3~ and P(i__PrNCH~2~CH~2~)~3~N. The latter is one of the most basic trivalent phosphorus compounds [p__K~a~(acetonitrile) 33.6]. Complexes 5 a–c and 6 b are effective ligands for Pd(OAc)~2~‐catalyzed Suzuki coupling reactions: 6 b gave a catalyst nearly as active as the benchmark organophosphine P__t__Bu~3~; 5 a, with a less bulky and electron‐rich PR~2~ moiety, gave a less active catalyst. The reaction of 5 a and [(η^3^‐C~3~H~5~)Pd(NCPh)~2~]^+^ BF~4~^−^ gave the bridging phosphido complex [(η^5^‐C~5~H~5~)Ru(PEt~3~)~2~(PPh~2~)Pd(NCPh)(η^3^‐C~3~H~5~)]^+^ BAr~F~^−^ in approximately 90 % purity. The crystal structure of 4 a is described, as well as substitution reactions of 3 b and 4 b.