Synthesis, Structure, and Temperature-Dependent Dynamics of Neutral Palladium Allyl Complexes of Annulated Diaminocarbenes and Their Catalytic Application for C−C and C−N Bond Formation Reactions

Abstract

Imidazolinium salts 7,9-bis(2,4,6-trimethylphenyl)-6b,9a-dihydroacenaphtho [1,2-d]imidazolinium tetrafluoroborate and 7,9-bis(2,6-diisopropylphenyl)-6b,9a-dihydroacenaphtho[1,2-d]imidazolinium tetrafluoroborate, designated as [(BIAN-SIMes)(H)]BF 4 (3a) and [(BIAN-SIPr)(H)]BF 4 (3b), respectively, have been prepared and structurally characterized. The molecular structure of 3a shows the presence of a bifurcated hydrogen bond between the tetrafluoroborate anions and the central imidazolinium proton (-NCHN-). The palladium(II) complexes (η 3 -C 3 H 5 )Pd(BIAN-SIMes)Cl (5a) and (η 3 -C 3 H 5 )Pd(BIAN-SIPr)Cl ( 5b) have been synthesized. The temperature-dependent NMR behavior of σ-bonded palladium(II) complex 5b was studied. The crystal structure of 5b shows a localized single and double bond between the allyl ligand. The catalytic activities of the palladium(II) complexes 5a and 5b have been evaluated for Suzuki-type C-C coupling and for room-temperature C-N bond formation using aryl halides.

Synthesis and Characterisation of Mono‐ and Bidentate Alkoxybenzimidazolin‐2‐ylidene Palladium Complexes: Interesting Solution Behaviour and Application in Catalysis

“…This phenomenon has previously been described by Pörschke and co-workers in their studies of allyl Pd adducts with phosphanes, [18] and similar fluxional behaviour was recently reported for a mixed NHC/ allyl palladium complex. [19] The formation of a σ-allyl intermediate bonded to Pd via C 3 ( Figure 3) is consistent with the greater trans influence of the NHC compared to the chloride ligand. Stronger bonding between Pd and C 3 (trans to Cl) compared to C 1 (trans to the NHC) is also suggested by the shorter Pd-C 3 bond length seen in the solid state (see Structure determinations).…”

Easy Entry into Reduced Ar‐BIANH2 Compounds: A New Class of Quinone/Hydroquinone‐Type Redox‐Active Couples with an Easily Tunable Potential

“…It is worth mentioning that sterically hindered Ar‐BIAN compounds (Ar=2,4,6‐Me 3 C 6 H 2 , 2,6‐ i Pr 2 C 6 H 3 ) have already been reported in the literature to be reduced by NaCNBH 3 or LiAlH 4 93–94. However, in both cases the reduction proceeded to the tetrahydro derivative and the formation of an intermediate reduction product was not mentioned.…”

“…During the voltammetric studies described in the next paragraph, we wished to have in our hands the tetrahydrogenated derivative of p ‐CH 3 C 6 H 4 ‐BIAN (indicated in the following as p ‐CH 3 C 6 H 4 ‐BIANH 4 , 3 e ) having a fully saturated series of NCCN bonds. In the literature, tetrahydrogenation of a BIAN derivative has been reported only for the sterically hindered 2,6‐ i Pr 2 C 6 H 3 ‐BIAN or 2,4,6‐Me 3 C 6 H 3 ‐BIAN in two papers, using NaCNBH 3 93 or LiAlH 4 ,94 respectively, as reducing agents. Both cis and trans N,N isomers can be formed with respect to the acenaphthene plane Scheme ), but only the cis isomer was described in both papers.…”

Synthesis and catalytic activity of supported acenaphthoimidazolylidene N-heterocyclic carbene ruthenium complex for ring closing metathesis (RCM) and ring opening metathesis polymerization (ROMP)

“…[8][9][10][11] Transition-metal complexes of Aryl-BIAN ligands ( Figure 1) have proven to be efficient homogenous catalysts for a number of organic reactions. In particular, BIAN ligands have contributed to palladium-catalyzed cross-coupling reactions to form C-C, [12][13][14][15] and C-N 16,17 bonds, selective hydrosilylation of carbonyl compounds using iron complexes, 18 Nickel-catalyzed olefin polymerization, 19 nucleophilic trifluoromethoxylation of organic halides by silver (I) complexes, 20 and the catalytic hydroformylation of 1-octene using rhodium (I) complexes. 21 However, the examples of ruthenium based-BIAN complexes are much fewer than other transition metal complexes (Figure 1).…”