“…The formation of these chloride species in the presence of Au I is also possible even at room temperature instead of 50 °C. There is some precedent for the facile activation of CH 2 Cl 2 in the presence of transition metals, such as Zn or Co,16 Rh,17 and Mg/TiCl 4 /THF,18 but as far as we know, the instability of CH 2 Cl 2 was not detected previously with 2‐di‐ tert ‐butylphosphanylbiphenyl Au I or Cu I complexes as catalysts. We tested the catalytic activity of this neutral gold(I) complex [LAuCl] ( 10 ; Table 1, entries 5 and 6) for the Mannich A 3 coupling and found that it was considerably less active than the initial precatalyst Cu I complexes 3 and 5 and the Au I complexes 6 and 7 .…”
Care should be exercised when using CH2Cl2 as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. CuI and AuI deactivation has been proved for the Mannich three‐component coupling reaction. A series of CuI and AuI complexes with potential mechanistic implications were isolated and characterized by X‐ray crystallography.
“…The formation of these chloride species in the presence of Au I is also possible even at room temperature instead of 50 °C. There is some precedent for the facile activation of CH 2 Cl 2 in the presence of transition metals, such as Zn or Co,16 Rh,17 and Mg/TiCl 4 /THF,18 but as far as we know, the instability of CH 2 Cl 2 was not detected previously with 2‐di‐ tert ‐butylphosphanylbiphenyl Au I or Cu I complexes as catalysts. We tested the catalytic activity of this neutral gold(I) complex [LAuCl] ( 10 ; Table 1, entries 5 and 6) for the Mannich A 3 coupling and found that it was considerably less active than the initial precatalyst Cu I complexes 3 and 5 and the Au I complexes 6 and 7 .…”
Care should be exercised when using CH2Cl2 as a solvent for reactions in which amines are a reagent, since undesirable deactivation of cationic copper(I) and gold(I) catalysts to form the corresponding inactive neutral chloride complexes [LMCl] (M=Cu or Au) can occur as a result of the generation of hydrogen chloride in the medium. CuI and AuI deactivation has been proved for the Mannich three‐component coupling reaction. A series of CuI and AuI complexes with potential mechanistic implications were isolated and characterized by X‐ray crystallography.
“…If the mononuclear complex contains a nonmetal basic center, an insertion of the methylene group between the metal and this heteroatom has been observed, providing evidence for the possibility of breaking both C−Cl bonds. (b) Methylene-bridged complexes also occur by an unusual two-center three-fragment oxidative-addition reaction of dichloromethane to dinuclear complexes. (c) Schrock-type carbene complexes have been recently described as the product from a three-fragment oxidative-addition reaction on a single metal center in mononuclear ruthenium(0) complexes, with easily removable dihydrogen or dinitrogen ligands …”
Reactions of [{Rh(μ-Pz)(CNBut)2}2] (Pz = pyrazolate, 1) with dichloromethane, α,α-dichlorotoluene, 1,1-dichloroacetone, and methyldichloroacetate gave the functionalized methylene-bridged compounds [{Rh(μ-Pz)(Cl)(CNBut)2}2(μ-CHR)] (R = H, Ph, COMe, CO2Me),
respectively. The molecular structure of [{Rh(μ-Pz)(Cl)(CNBut)2}2{μ-CH(CO2Me)}] was
determined by an X-ray diffraction study. Similarly, the thiolate complex [{Rh(μ-SBut)(CNBut)2}2] was reacted with dichloromethane to give [{Rh(μ-SBut)(Cl)(CNBut)2}2(μ-CH2)].
The gem-dichloroalkanes are formally broken in three fragments that become a methylene-bridging group and two terminal chloride ligands in these two-center four-electron oxidative-addition reactions. Decreasing the nucleophilicity of the metals via steric effects, while
keeping the basicity of the metals constant, leads to a different type of product, as shown by
reaction of dichloromethane with [{Rh(μ-Me2Pz)(CNBut)2}2] to give [{Rh(μ-Me2Pz)(Cl)(CNBut)2}2]. A deeper insight into these reactions is provided by reactions of the complex
[(cod)Rh(μ-Pz)2Rh(CNBut)2] with methyl dichloroacetate and dichloromethane to give the
mixed-valence Rh(I)−Rh(III) complex [(cod)Rh(μ-Pz)2Rh(Cl){η1-CHCl(CO2Me)}(CNBut)2] and
the methylene-bridged complex [(cod)(Cl)Rh(μ-Pz)2(μ-CH2)Rh(Cl)(CNBut)2], respectively. The
former evidences that the above rections take place in two steps and that the second step
involves an internal oxidative-addition reaction following an SN2 mechanism. The latter
reaction is very suggestive of how cooperative effects can act in a dinuclear complex to induce
an unusual reactivity.
“…The palladium(0) complex 4 is very reactive toward oxidative addition reaction. Thus, treatment of 4 with dichloromethane at room temperature results in the formation of a palladium(II) complex, Mo 2 Pd 2 Cl 2 (CH 2 Cl) 2 (pyphos) 4 ( 6 ) (eq 1), which is a rare example of the oxidative addition of dichloromethane to a Pd(0) center, e.g., mononuclear Pd(0) complexes , and a dinuclear Pd(0) complex, Pd 2 (dpm) 3 (dpm = bis(diphenylphosphino)methane), , though oxidative addition of dichloromethane to d 9 species, Rh(I) and Ir(I), readily proceeded. − …”
mentioning
confidence: 99%
“…Thus, treatment of 4 with dichloromethane at room temperature results in the formation of a palladium(II) complex, Mo 2 Pd 2 Cl 2 (CH 2 Cl) 2 (pyphos) 4 (6) (eq 1), 12 which is a rare example of the oxidative addition of dichloromethane to a Pd(0) center, e.g., mononuclear Pd(0) complexes 13,14 and a dinuclear Pd(0) complex, Pd 2 (dpm) 3 (dpm ) bis(diphenylphosphino)methane), 15,16 though oxidative addition of dichloromethane to d 9 species, Rh(I) and Ir(I), readily proceeded. [17][18][19][20][21] The crystal structure of 6 is shown in Figure 2; 22 there is a 2-fold axis perpendicular to the Mo-Mo vector passing through the center of the Mo-Mo bond. Four of the metal atoms, Pd, Mo, Mo, and Pd, are aligned linearly.…”
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