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

Abstract

A series of mono(diene)-and bis(diene)rhodium(i) compounds (diene butadiene, 2-methylbutadiene (isoprene), and 2,3-dimethylbutadiene) was prepared from the triflato-bridged dimer [Rh{m-O 2 S(O)CF 3 }(C 8 H 14 ) 2 ] 2 (1). Reaction of 1 with excess diene affords the monomeric complexes [Rh{h 1

A New Spin on Cyclooctatetraene (COT) Redox Activity: Low-Spin Iron(I) Complexes That Exhibit Antiferromagnetic Coupling to a Singly Reduced η4-COT Ligand

“…1.428(4) 1.428(5) 1.430(5) 33 1.424 (5) 1.425(5) 1.426( 5) η 3 ,η 4 -COT) 38 have been excluded from Table 2, since these complexes feature unusual μ-η 4 ,η 4 -COT and μ-η 3 ,η 4 -COT binding modes, respectively, in which one or more of the η 4 -COT carbon atoms are coordinated to both metal centers. While population of the lowest lying COT π* orbital might not be achieved for the second-and third-row complexes shown in Table 2, it is important to note that several of the first-row complexes listed feature significant C(1)−C(2)/C(3)−C(4) bond elongation with concomitant C(2)−C(3) bond shortening, indicating that they could in fact have an electronic structure best described as having an η 4 -COT radical monoanionic or dianionic ligand.…”

“…This premise has been explored computationally, and seemingly accurate electronic structure descriptions can often be reached following close inspection of crystallographically determined diene metrical parameters . For example, the solid-state structure of (η 4 -2-methyl-1,3-butadiene) 2 Rh(O 3 SCF 3 ) has been found to feature diene ligand olefin distances of 1.406(2), 1.397(2), 1.395(2), and 1.396(2) Å with bridging C–C bond distances of 1.441(2) and 1.443(2) Å, suggesting that each η 4 -diene behaves as a neutral ligand as opposed to a dianion. While this approach to electronic structure assignment remains appropriate for many η 4 -diene complexes, especially when considering low-spin second- and third-row metal complexes that do not exhibit a great degree of back-bonding, this methodology remains a drastic oversimplification for complexes of the first transition series, as the possibility for single-electron promotion into the lowest energy diene antibonding orbital is often overlooked.…”

“…40 Like Fe(CO) 5 , 41 1-κ 2 -Triphos was found to possess a near trigonal bipyramidal geometry in the solid state (see Figure S5 and Table S4 of the Supporting Information).…”

“…27 Since the C-C (Table 2) and M-C (Table 5) In addition to its potential impact on fundamental electronic structure investigations, the research described herein may also hold implications for the mechanistic study of N-heterocyclic carbene promoted COT ligand coupling reactions. 46 In a recent report by Grubbs and co-workers, it was found that the addition of N-heterocyclic carbene to two equivalents of Fe(COT) 2 allowed for the isolation of (η 4 -COT)Fe(μ-η 5 (Table 4). 19 Although the C(1)-C(2) and C(3)-C(4) distances of 1.447(3) and 1.400(4) Å appear to be somewhat unusual, the other COT and Fe-C distances suggest that this complex may feature an η 4 -COT radical monoanion, rather than a neutral η 4 -COT ligand.…”

Improving intramolecular hydroamination Rh(i) and Ir(i) catalysts through targeted ligand modification

“…The Rh-O bond lengths for Rh-OSO 2 CF 3 in 10 and 11 are at the lower end of the Rh-O bond distances that are reported in the literature for rhodium triflate complexes. [30][31][32][33][34][35][36] The Rh-P bonds trans to the chloride anion in 4 and 8 (2.22(7) and 2.21(9) A ˚, respectively) are similar, within error, to the Rh-P bonds of 10 and 11 (2.20(1) and 2.18(7) A ˚, respectively) which are trans to OSO 2 CF 3…”