Copper complexes phosphine ligands

Dopamine /3-hydroxylase (D/3H) is a copper-containing glycoprotein that hydroxylates dopamine at the benzylic position to norepinephrine.84 During the attempted crystallization of the bis(hydroxide)-bridged dicopper(II) dimer, a side product was subsequently isolated (complex (63)), revealing intramolecular hydroxylation at a formally benzylic position of the tris(imidazo-lyl)phosphine ligand.85 The copper(II) center has an axially compressed TBP structure. 

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. 

Phosphine Ligand Derivatives of Iron(II)—Copper(I) Complexes 173... 

While today the construction of such bidentate phosphine ligands with the use of an assembly metal is referred to as supramolecular chemistry, this is not to say that there are no examples in older literature utilizing this principle. Actually, there are many and using as a search term hetero bimetallic complexes (a named coined in the early 1980s) leads us to a plethora of complexes. For instance in complex 29, reported by Rauchfuss in 1982, one would consider copper as the assembly metal and platinum as the potential catalytic metal [70]. 

Bromothiophene has been coupled with phenylacetylene in a copper-free reaction to give a 96% yield of the product (Equation 33) <20030L4191>. A Pd(ll) complex containing the ferrocene-based phosphinimine-phosphine ligand 83 has proved very efficient for the reaction of 2-iodo- and 2-bromothiophene with phenylacetylene the coupling takes place under copper- and amine-free conditions (Equation 34) <2004TL4337>. 

Bi8 tri(cyclohexyl)phosphine copper(I) perchlorate is obtained on refluxing the tertiary phosphine with copper(II) perchlorate in ethanol smaller tertiary phosphines give [Cu(PR3)4]C104 complexes thus, this complex is obtained because of the impossibility of coordinating more than two tri(cycIohexyl)phosphine ligands to one copper atom 248). 

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