Reactivity of Alkyne Insertion and Catalytic Activity of Five‐ and Six‐Membered Cyclometalated Phosphine Complexes of Iridium

Abstract

Reactions of three aryl-substituted phosphines with [Cp*IrCl 2 ] 2 afforded the corresponding five-membered or sixmembered cyclometalated iridium complexes (2 or 5,6) via an intramolecular C(sp 2 )-H bond activation. Insertion reactions of the five-membered cycloiridated complex 2 with PhC≡CPh and PhC≡CCOPh resulted in the corresponding five-membered and six-membered doubly cycloiridated complexes 7 and 8, the formation of which presumably went through the vinylidene rearrangement of alkynes followed by 1,1-insertion; while the reactions of the six-membered cyclometalated complexes 5, 6 [a] 3195 with PhC≡CPh or PhC≡CCOPh gave the corresponding eightmembered cycloiridated complexes 9-12 by 1,2-insertion. The hydrosilylation of imines catalyzed by five-or six-membered P-containing cycloiridated complexes were studied, and the results proved that the six-membered cycloiridated complex 5 can be used as an efficient catalyst, which was applied for the hydrosilylation of various imines, especially aldimines. Molecular structures of complexes 9, 10 and 12 were determined by X-ray diffraction. Results and Discussion Reaction of [Cp*IrCl 2 ] 2 with Benzyldiphenylphosphine (1)Reaction of [Cp*IrCl 2 ] 2 with benzyldiphenylphosphine in the presence of sodium acetate at room temperature result in the expected five-membered cyclometalated complex 2 in the yield of 62 % (Scheme 1). Obviously, the formation of complex 2 involves an intramolecular C(sp 2 )-H bond activation. The 1 H NMR spectrum of 2 showed several groups of multiplets in the aromatic region, all integrating to 14 H due to the phenyl rings, two doublets at δ = 3.92 and 3.75 ppm assigned to signal for the methylene group, and a doublet at δ = 1.55 corresponding to five methyl groups of Cp*; the 31 P NMR spectrum exhibited a peak at δ = 32.81, which is consistent with the data (32.1) reported for the (1-naphthyl)diphenylphosphine analogue Cp*IrClPPh 2 (η 1 -C 10 H 6 ). [10] Scheme 1. Reaction of [Cp*IrCl 2 ] 2 with benzyldiphenylphosphine (1). Reactions of [Cp*IrCl 2 ] 2 with 2-(Diphenylphosphino)biphenyl (3) and 2-(Diisopropylphosphino)biphenyl (4)First, the phosphines 3 and 4 were chosen as ligands for the reason that they could provide a C(sp 2 )-H bond at the appropri-Full Paper ate position only for constructing the six-membered metallacycle. Similarly, reactions of [Cp*IrCl 2 ] 2 with ligands 3 and 4 in the presence of sodium acetate at room temperature resulted in the corresponding six-membered iridacycles 5 and 6 in high yields of 95 % and 94 % respectively (Scheme 2). The 1 H NMR spectrum of 6 showed six groups of peaks in the aromatic region, all integrating to 8 H due to the biphenyl unit, these resonances indicated that one aromatic C(sp 2 )-H bond is activated in the reaction to form the six-membered cyclometalated complex 6; the 31 P NMR spectrum exhibited a peak at δ = 9.28 ppm, which is significantly low-frequency shifted compared with the five-membered analogue.Scheme 2. Reactions of [Cp*IrCl 2 ] 2 with 2-(diphenylphosphino)biphenyl (3) and 2-(dii...

Transmetallation of Bis(6‐diphenylphosphinoacenaphth‐5‐yl)‐Mercury and ‐Tributyltin with Precious Metal Chlorides

“…At present, there is great interest in peri-substituted 8-diorganophosphinonaphth-1-yl and 6-diorganophosphinoacenaphth-5-yl precious metal compounds of Re, [1] Ru, [2,3] Ir, [4] Rh, [5] and particularly, Au, [6][7][8][9][10][11][12][13][14][15][16] which involves the synthesis, bonding analysis and applications in bond activation and catalysis. Often, the synthesis of these compounds entails the oxidative addition of the metal to a C-H [1][2][3][4][5] or C-X (X = halide) bond in peri-position to a structurally directing P atom that takes part in coordination to the precious metal.…”

“…At present, there is great interest in peri-substituted 8-diorganophosphinonaphth-1-yl and 6-diorganophosphinoacenaphth-5-yl precious metal compounds of Re, [1] Ru, [2,3] Ir, [4] Rh, [5] and particularly, Au, [6][7][8][9][10][11][12][13][14][15][16] which involves the synthesis, bonding analysis and applications in bond activation and catalysis. Often, the synthesis of these compounds entails the oxidative addition of the metal to a C-H [1][2][3][4][5] or C-X (X = halide) bond in peri-position to a structurally directing P atom that takes part in coordination to the precious metal. [6][7][8][9][10][11][12][13][14] Recently, we have used the well-defined 5-diorganophosphinoacenaphth-6-yllithium, RLi (1, R = 5-Ph 2 P-Ace-6-), [17] as starting material for the synthesis of two related transmetallation reagents R 2 Hg (2, R = 6-Ph 2 P-Ace-5-) [15] and RSnBu 3 (3, R = 6-Ph 2 P-Ace-5-), [18] which offer the advantage to be nonreductive and bench stable (Scheme 1).…”

“…[6][7][8][9][10][11][12][13][14] Recently, we have used the well-defined 5-diorganophosphinoacenaphth-6-yllithium, RLi (1, R = 5-Ph 2 P-Ace-6-), [17] as starting material for the synthesis of two related transmetallation reagents R 2 Hg (2, R = 6-Ph 2 P-Ace-5-) [15] and RSnBu 3 (3, R = 6-Ph 2 P-Ace-5-), [18] which offer the advantage to be nonreductive and bench stable (Scheme 1). [19] The reaction of mercury reagent 2 with (tht)AuCl gave rise to the formation of the complex R 2 Hg•AuCl (4), in which the two transition ARTICLE metals are in close proximity and engage in Au•••Hg metallophilic interaction (Scheme 1). During the course of a few days, 4 converts in the cationic gold(III) complex cis-[R 2 Au][Cl] (5), whereby elemental Hg was expelled (Scheme 1).…”

Recent Development in the Synthesis and Catalytic Application of Iridacycles

“…In 2018, Zhu et al. reported phosphine‐containing five‐, six‐ and eight‐membered cycloiridated complexes, including their insertion reactions with aromatic alkynes [91] . The iridacycles were screened for their catalytic activities in the hydrosilylation of N ‐benzylideneaniline, the most active being the six‐membered iridacycle 98 .…”

“…In 2018, Zhu et al reported phosphine-containing five-, six-and eight-membered cycloiridated complexes, including their insertion reactions with aromatic alkynes. [91] The iridacycles were screened for their catalytic activities in the hydrosilylation of N-benzylideneaniline, the most active being the six-membered iridacycle 98. The complex was applied to the hydrosilylation of various aldimines and ketimines, affording the corresponding amines in 35-98 % yields (Scheme 48).…”