Ligand substituent effects

Thomas KE, Wasbotten IH, Ghosh A (2008) Copper P-octakis(trifluoromethyl)corroles new paradigms for ligand substituent effects in transition metal complexes. Inorg Chem 47 10469-10478... 

Distribution may be affected by unresolved ligand substituent effects... 

Ligand-substituent effects on hydrovinylation of 2-methoxy-6-vinylnaph-... 

Nielsen, D.J., CaveU, K.J., Skelton, B.W. and White, A.H. (2006) Methyl-palladium(U) complexes of pyridine-bridged bis(nucleophilic heterocyclic carbene) ligands substituent effects on structure, stabUity, and catalytic performance. Inorg. Chim. Acta, 359, 1855-69. 

Cadmium(Il) —Ligand substituent effects have been explored for the reaction... 

Terphenyl Ligand Substituent Effects in Chromium Complexes. 86... 

Substituent effects hae been observed in a series of substituted malonato complexes (167). The 9Be resonance frequencies move to higher field as the basicity of the ligand increases, as can be seen in Table XI. Quadrupolar broadening is considerable in complexes of the hydrolyzed trimer, so much so that unless a species of this sort is present in high concentration relative to the others, its signal may be buried in the baseline noise. The tetrahedron is significantly distorted from Td symmetry in these compounds. 

The orange complex 83 (57) exhibits a pseudotetrahedral geometry in the solid state, with the chlorine atoms distorted 49° and 63° away from the bipyridyl-Cu plane (Fig. 8). The d-d transition occurs at 919 nm. It seems likely that the large size of the ligand substituent is responsible for the deviation in the structure of the copper complex. Whether this effect is also responsible for the ease of reduction of the corresponding triflate complex by diazoester is not clear. 

The utility of bis(oxazoline)-Cu(II) complexes as catalysts for the Diels-Alder reaction has been examined in a number of other systems. Aggarwal et al. (205) demonstrated that a-thioacrylates behave as effective two-point binding substrates for these catalysts. With cyclopentadiene, catalyst 271d induces the reaction at -78°C to provide the cycloadduct in 94 6 diastereoselectivity and >95% ee. Aggarwal proposes that the metal binds to the carbonyl oxygen and to the sulfur atom. The sulfur substituent is placed opposite the ligand substituent thereby shielding the bottom face of the alkene. Considerably lower selectivities are observed with 5-Me substrates. 

Gs, trans, or metal effects occur when, e.g., an octahedral coordination compound ML6 [7] is transformed into a new complex, either MLSX [2], where a ligand has been altered, or M L6 [5], where the metal M has been replaced by an isovalent metal M. The comparison of either [2] with [7], or [2] with [7], discloses either cis and trans effects or metal effects inasmuch as the properties of the ligands L are altered by this variation in the first case, the substituent effect of X is subdivided into the cis and trans effects. 

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