- Award ID(s):
- 1954480
- NSF-PAR ID:
- 10217674
- Date Published:
- Journal Name:
- Dalton Transactions
- Volume:
- 49
- Issue:
- 35
- ISSN:
- 1477-9226
- Page Range / eLocation ID:
- 12287 to 12297
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
The gyroscope like dichloride complexes trans -Pt(Cl) 2 (P((CH 2 ) n ) 3 P) ( trans -2; n = c, 14; e, 18; g, 22) and MeLi (2 equiv.) react to yield the parachute like dimethyl complexes cis -Pt(Me) 2 (P((CH 2 ) n ) 3 P) ( cis -4c,e,g, 70–91%). HCl (1 equiv.) and cis -4c react to give cis -Pt(Cl)(Me)(P((CH 2 ) 14 ) 3 P) ( cis -5c, 83%), which upon stirring with silica gel or crystallization affords trans -5c (89%). Similar reactions of HCl and cis -4e,g give cis / trans -5e,g mixtures that upon stirring with silica gel yield trans -5e,g. A parallel sequence with trans -2c/EtLi gives cis -Pt(Et) 2 (P((CH 2 ) 14 ) 3 P) ( cis -6c, 85%) but subsequent reaction with HCl affords trans -Pt(Cl)(Et)(P((CH 2 ) 14 ) 3 P) ( trans -7c, 45%) directly. When previously reported cis -Pt(Ph) 2 (P((CH 2 ) 14 ) 3 P) is treated with HCl (1 equiv.), cis - and trans -Pt(Cl)(Ph)(P((CH 2 ) 14 ) 3 P) are isolated (44%, 29%), with the former converting to the latter at 100 °C. Reactions of trans -5c and LiBr or NaI afford the halide complexes trans -Pt(X)(Me)(P((CH 2 ) 14 ) 3 P) ( trans -9c, 88%; trans -10c, 87%). Thermolyses and DFT calculations that include acyclic model compounds establish trans > cis stabilities for all except the dialkyl complexes, for which energies can be closely spaced. The σ donor strengths of the non-phosphine ligands are assigned key roles in the trends. The crystal structures of cis -4c, trans -5c, trans -7c, and trans -10c are determined and analyzed together with the computed structures.more » « less
-
Warren Piers (Ed.)Although cobalt( i ) bis-phosphine complexes have been implicated in many selective C–C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt( i )-bis-phosphine complexes and their use in Co( i )-catalyzed reactions. We find that easily prepared ( in situ generated or isolated) bis-phosphine and (2,6- N -aryliminoethyl)pyridine (PDI) cobalt( ii ) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li 3 N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt( i ) complex crystallizes as a phosphine-bridged species [(P∼P)(X)Co I [μ-(P∼P)]Co I (X)(P∼P)] or a halide-bridged species [(P∼P)Co I [μ-(X)] 2 Co I (P∼P)]. Because the side-products are innocuous, these methods can be used for the in situ generation of catalytically competent Co( i ) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P∼P)Co I -η 4 -diene] + X − or [(P∼P)Co I -η 6 -arene] + X − complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented.more » « less
-
Summary The collaborative non‐self‐recognition model for S‐
RN ase‐based self‐incompatibility predicts that multiple S‐locus F‐box proteins (SLF s) produced by pollen of a givenS ‐haplotype collectively mediate ubiquitination and degradation of all non‐self S‐RN ases, but not self S‐RN ases, in the pollen tube, thereby resulting in cross‐compatible pollination but self‐incompatible pollination. We had previously used pollen extracts containingGFP ‐fused S2‐SLF 1 (SLF 1 with anS 2‐haplotype) ofPetunia inflata for co‐immunoprecipitation (Co‐IP ) and mass spectrometry (MS ), and identified PiCUL 1‐P (a pollen‐specific Cullin1), PiSSK 1 (a pollen‐specific Skp1‐like protein) and PiRBX 1 (a conventional Rbx1) as components of theSCFS 2–SLF 1complex. Using pollen extracts containing PiSSK 1:FLAG :GFP for Co‐IP /MS , we identified two additionalSLF s (SLF 4 andSLF 13) that were assembled intoSCFSLF complexes. As 17 genes (SLF toSLF 1 ) have been identified inSLF 17S 2andS 3pollen, here we examined whether all 17SLF s are assembled into similar complexes and, if so, whether these complexes are unique toSLF s. We modified the previous Co‐IP /MS procedure, including the addition of style extracts from four differentS ‐genotypes to pollen extracts containing PiSSK 1:FLAG :GFP , to perform four separate experiments. The results taken together show that all 17SLF s and anSLF ‐like protein,SLFL ike1 (encoded by anS ‐locus‐linked gene), co‐immunoprecipitated with PiSSK 1:FLAG :GFP . Moreover, of the 179 other F‐box proteins predicted byS 2andS 3pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co‐immunoprecipitated with PiSSK 1:FLAG :GFP . These results suggest thatSCFSLF complexes have evolved specifically to function in self‐incompatibility. -
Some reactions produce extremely hot nascent-products which nevertheless can form sufficiently long-lived van der Waals (vdW) complexes—with atoms or molecules from a bath gas—as to be observed via microwave spectroscopy. Theoretical calculations of such unbound resonance-states can be much more challenging than ordinary bound-state calculations depending on the approach employed. One encounters not only the floppy, and perhaps multi-welled potential energy surface (PES) characteristic of vdWs complexes, but in addition must contend with excitation of the intramolecular modes and its corresponding influence on the PES. Straightforward computation of the (resonance) rovibrational levels of interest, involves the added complication of the unbound nature of the wavefunction, often treated with techniques such as introducing a complex absorbing potential. Here, we have demonstrated that a simplified approach of making a series of vibrationally effective PESs for the intermolecular coordinates—one for each reaction product vibrational quantum number of interest—can produce vdW levels for the complex with spectroscopic accuracy. This requires constructing a series of appropriately weighted lower-dimensional PESs for which we use our freely available PES-fitting code AUTOSURF. The applications of this study are the Ar–CS and Ar–SiS complexes, which are isovalent to Ar–CO and Ar–SiO, the latter of which we considered in a previously reported study. Using a series of vibrationally effective PESs, rovibrational levels and predicted microwave transition frequencies for both complexes were computed variationally. A series of shifting rotational transition frequencies were also computed as a function of the diatom vibrational quantum number. The predicted transitions were used to guide and inform an experimental effort to make complementary observations. Comparisons are given for the transitions that are within the range of the spectrometer and were successfully recorded. Calculations of the rovibrational level pattern agree to within 0.2 % with experimental measurements.more » « less
-
The reduction potentials (reported vs. Fc + /Fc) for a series of Cp′ 3 Ln complexes (Cp′ = C 5 H 4 SiMe 3 , Ln = lanthanide) were determined via electrochemistry in THF with [ n Bu 4 N][BPh 4 ] as the supporting electrolyte. The Ln( iii )/Ln( ii ) reduction potentials for Ln = Eu, Yb, Sm, and Tm (−1.07 to −2.83 V) follow the expected trend for stability of 4f 7 , 4f 14 , 4f 6 , and 4f 13 Ln( ii ) ions, respectively. The reduction potentials for Ln = Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, that form 4f n 5d 1 Ln( ii ) ions ( n = 2–14), fall in a narrow range of −2.95 V to −3.14 V. Only cathodic events were observed for La and Ce at −3.36 V and −3.43 V, respectively. The reduction potentials of the Ln( ii ) compounds [K(2.2.2-cryptand)][Cp′ 3 Ln] (Ln = Pr, Sm, Eu) match those of the Cp′ 3 Ln complexes. The reduction potentials of nine (C 5 Me 4 H) 3 Ln complexes were also studied and found to be 0.05–0.24 V more negative than those of the Cp′ 3 Ln compounds.more » « less