The reaction of PNPRuCl (PNP = ((Bu2PCH2SiMe2)-Bu-iota)(2)N-) with excess MeLi at -78 degrees C, followed by addition of a one-electron oxidant, leads to the thermally stable (at 25 degrees C), low-spin, five-coordinate trivalent ruthenium complex PNPRuMe2, 1. For comparison PNPRuI2, 2, was also synthesized and shown equally to be a low-spin d(5) complex. Compound 1 reacts with NO to produce the diamagnetic ruthenium(II) complex PNPRuMe2(NO), 3, with H-2 to give PNPRu(H)(3), 5, and with excess CO to produce PNPRu(COMe)CO, 6. The unusual stability of 1 is suggested to arise from the steric encapsulation of the radical center provided by the extremely bulky pincer ligand, the low coordination number (5), and a non-redox-innocent amide functionality.

Synthesis and characterization of Cp*Ru[eta3-HC(PPh2NPh)2], 1, reveals it to have a "piano stool" structure with the ligand bound to Ru(II) via two N and the unique, sp3 hybridized carbon. While the analogous (cymene) Ru[eta3-HC(PPh2NPh)2]+ does not react with CO, under the same conditions, 1 adds one CO rapidly (25 degrees C, 1 atm CO). Characterization, including an X-ray structure determination, shows that CO has displaced one chelate ligand nitrogen, which then hangs off the molecule, free of Ru. DFT calculations reveal a possible mechanism via a remarkably low energy (+9.3 kcal/mol) intermediate, pendant N, but with one phenyl on phosphorus stabilizing Ru via donation from a C(ipso)=C(ortho) bond. DFT calculations show that the electronic energy change for binding CO is over 20 kcal/mol less favorable for cymene than for C5Me5- as ligand; the reactivity difference is thus thermodynamic in origin.

Analysis of the results of DFT(PBE) calculations on a variety of species containing a "RuC-(PPh2NPh)(2)" subunit led to the proposal that this should be considered as an example where an Ru/C single bond is present, which leaves a stereochemically active lone pair on the "carbene" carbon and thus a pyramidal, quasi-spa hybridization for carbon. General applications of this idea are discussed, the possible protonation of this carbon lone pair is described, and a DFT(PBE) geometry optimization of the two species (Cl)(n)RuHC(PPh2NPh)(2)((1-n)+) with n = 0, 1 reveals a potential for oxidative addition of the P/N bond of this ligand to Ru, to generate an RuNPh moiety. The crystal structure of the triflate (CF3SO3-) salt of the C-protonated species (Cymene)Ru[H*C(PPh2NPh](2)](+) shows that H* hydrogen bonds to triflate.

Der Ring schließt sich schneller bei den MoIV-Komplexen von Endithiolat-Endiinen (siehe Schema; S gelb, Mo rot) als bei den entsprechenden nichtkomplexierten Endiinen. Erklärt wird diese Beobachtung mit einer langreichweitigen elektronischen Polarisation durch das Metallzentrum. Ligand-Metall-Charge-Transfer der C2S4-Einheit und Ladungsabstoßung im Übergangszustand senken die Aktivierungsbarriere der Cyclisierung. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2005/z461825_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Tetradentate metalloenediynes with strong imine and weaker thioether coordination serve as a geometrically non-rigid switch to drive thermal Bergman cyclization.

(PNPtBu)Re(H)(4), where PNPtBu is ((Bu2PCH2SiMe2)-Bu-t)(2)N, reacts at 23 degreesC with RCdropCH (R = Bu-t, SiMe3, Ph) to give first H-2 and mirror-symmetric (PNPtBu)ReH3(CCR), then H-2 and C-2v symmetric (PNPtBu)Re(CCR)(2). The diacetylide compounds show temperature-independent paramagnetism and C-13 and P-31 chemical shifts far beyond their normal values for other (PNPtBu)ReXn, compounds. Single-crystal X-ray diffraction shows very similar structures for the cases R = Ph and R = SiMe3, each having an approximately C-2v geometry with equivalent acetylides with angleC-Re-C approximately 108degrees. No hydride or H-2 ligands are detected in final difference Fourier maps. DFT(B3PW91) calculations give minimum energy geometries of these species, of their products upon adding H-2, and of mechanistically significant analogues [(H2PCH2SiH2)(2)N] ReHnR'(m),H2-m, with n = 0, 2, m = 1, 2, and R' = H or Ph. These calculated geometries, when compared to those from X-ray diffraction, indicate that the isolated compounds have no hydride or H-2 ligands and are thus (PNP)Re-III(CCR)(2), making them more unsaturated than the reagent (PNP)Re-v(H)(4) by two electrons. Triplet state geometries of (PNP)ReXY are calculated and analyzed, as are their frontier orbitals.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The macrocycle [2.1.1]-(2,6)-pyridinophane (L) binds to CuCl to give a monomeric molecule with tridentate binding of the ligand but in a distorted tetrahedral "3 + 1" geometry, where one nitrogen forms a longer (by 0.12 A) bond to Cu. In dichloromethane solvent this pyridine donor undergoes facile site exchange with a second pyridine in the macrocycle, to give time-averaged mirror symmetry. Both experimental and density functional theory studies of the product of chloride abstraction, using NaBAr(F)(4) in CH(2)Cl(2), show that the Cu(+) binds in a trigonal pyramidal, not planar, arrangement in LCu(+). This illustrates the ability of macrocyclic ligand constraint to impose an electronically unfavorable geometry on 3-coordinate Cu(I). LCuBAr(F)(4) and a triflate analogue LCu(I)(OTf) readily react with oxygen in dichloromethane to produce, in the latter case, a hydroxo-bridged dimer [LCu(II)(micro-OH)](2)(OTf)(2), of the intact (unoxidized) ligand L. Since the analogous LCuCl does not react as fast with O(2) in CH(2)Cl(2), outer-sphere electron transfer is concluded to be ineffective for oxidation of cuprous ion here.

Alcoholysis of [Fe6O2(OH)2(O2CBut)10(hep)2] (1) affords ferric wheels of different nuclearities: methanol yields [Fe10(OMe)20(O2CBut)10], whereas phenol gives the structurally unprecedented wheel [Fe8(OH)4(OPh)8(O2CBut)12], and the first to contain phenoxide.