Preparation, molecular structure and reactivity of mono- and di-nuclear sulfonato rhodium(I) complexes

A Series of (Butadiene)rhodium(I) Complexes with an Open-Sandwich- or Half-Sandwich-Type Structure

“…The Rh(1) ± P(1) distance in 5 a of 2.411(2) is rather long, possibly due to steric repulsion between the bulky phosphane ligand and the diene systems. As a result, the planes of the C 4 H 6 ligands are not parallel to each other but tilted by 16.6(8) [1] and 2 or 3 (1.0 equiv). In contrast, the reaction of 9 with an equimolar amount of 2,3-dimethylbutadiene gave the mono(diene) complex [Rh{h 1 -OS(O) 2 CF 3 }-(PiPr 3 )(h 4 -C 6 H 10 )] (8) as a red, moderately air-stable solid in 77 % yield (Scheme 2).…”

“…The Rh ± P distance of 2.329 (1) is almost the same as in other four-coordinate (triisopropylphosphane)rhodium(I) compounds. [1,14] Furthermore, the Rh ± O(1) distance of 2.136(3) in 8 is in good agreement with the Rh ± O bond length of 2.102(3) found in the structurally related complex [Rh{h 1 -OS(O) 2 -p-Tol}-(COD)(H 2 O)]. [12] As an extension of our studies on the reactivity of the bis(diolefin) complexes (outlined in Scheme 2), the sulfonato derivatives 2 and 3 were also treated with PiPr 3 (2.0 equiv) in acetone.…”

“…Treatment of a solution of 2, 3, or 4 in acetone with PiPr 3 (1.0 equiv) at room temperature leads to a change of color from yellow to orange, which, after work-up, gives the ionic complexes [Rh(h 4 -diene) 2 (PiPr 3 )]O 3 SCF 3 (5 ± 7) in good-toexcellent yield (Scheme 2). Compounds 5 ± 7 can also be prepared by treating the cyclooctene derivative [Rh{h 2 -O 2 S(O)CF 3 }(PiPr 3 )(C 8 H 14 )] (9) [1] with excess diene in pentane. Like the sulfonato complexes 2 ± 4, the phosphanesubstituted derivatives 5 ± 7 are insoluble in nonpolar organic solvents, but soluble in acetone and dichloromethane.…”

“…The RhÀP(1) and RhÀP(2) bond lengths of approximately 2.32 , as well as the bond angle P(1)-Rh-P(2) of 107.17(3)8, are quite similar to those of related cis-disposed bis(triisopropylphosphane)rhodium(i) derivatives. [1,15] With regard to the mechanism of formation of the pallylphosphonium complexes 10 and 11, there is no doubt that in the initial step the substitution products 5 and 6 are formed, which then possibly react with a second equivalent of PiPr 3 to give the cationic species [Rh(dien)( PiPr 3 ) 2 ] . It could be for steric reasons that treatment of these intermediates with a third molecule of the bulky triisopropylphosphane does not lead to the displacement of the diolefin ligand, but instead affords the allylphosphonium unit by attack of the phosphane on one of the terminal carbon atoms of the diene.…”

“…Depending on the substituent R on the sulfonato ligand, it was found that besides the three isomeric 1:1 adducts of C 2 H 4 and CPh 2 (1,1-diphenylprop-1-ene, 3,3-diphenylprop-1-ene, and 1,1-diphenylcyclopropane), quite unexpectedly, the 2:1 adduct 3,3-diphenylpent-1-ene was also formed. [1] Studies to elucidate the mechanism of this unusual CÀC coupling reaction revealed that, in the absence of diphenyldiazomethane, a rhodium(i)-catalyzed di-or oligomerization of ethene occurred.…”