Metal .pi. Complexes of Benzene Derivatives. 44. The (-PMe)2Co2(CO)4(PMe2-)2 Unit as a Spacer between Bis(.eta.-arene)metal Pairs (M = V, Cr). Electrochemical and EPR Spectroscopic Study of Interactions within the Tetranuclear Complexes

Abstract

In order to study long-distance intermetallic communication between bis(arene)metals, we have synthesized the binuclear complexes [(MeaP-^-CeHs^MhCoaCu-COMCOla (14, M = V; 15, M = Cr) in which the sandwich units are separated by the (-Me2P)2Co2(CO)4(P-ß2-)2 spacer. 14 crystallizes in the monoclinic space group P2\/c, Z = 4, a = 1465.2(3), b =

Exchange Interaction Mediated by O−H···O Hydrogen Bonds: Synthesis, Structure, and EPR Study of the Paramagnetic Organometallic Carboxylic Acid (η7-C7H7)V(η5-C5H4COOH)

“…While an evaluation of the J values for ( 2 • ) 2 and 3 • • based on metal−metal distances is unwarranted because both species are flexible in fluid solution, the number of intervening bonds, eight for ( 2 • ) 2 and six for 3 • • , may be a more reliable criterion. We have studied exchange coupling in organometallic biradicals with 3−8 bonds separating the two spin-bearing V(d 5 ) central metals and find the J values to follow a steady trend if plotted against the number of intervening bonds although the chemical nature of the bridges differs profoundly. A similar bond-counting strategy has been proposed to assess the gradation of the rates of long-distance electron-transfer along protein pathways, the view being taken that the decay per bond is not very sensitive to the different bond types in the chain 1c.…”

“…All manipulations were carried with exclusion of air under dinitrogen or argon (CV). Physical measurements were performed with the equipment specified previously …”

“…Physical measurements were performed with the equipment specified previously. 6 2 +/0 and of the hyperfine coupling constant a( 51 V, 2 • ) was performed in buffered aqueous solution (NaH 2PO4/CH3COONa/H3BO3, 0.2 M each) at 25 °C and adjustment of the required pH value with HCl or NaOH.…”

The [M2(CO)8] Complexes of the Cobalt Group

“…In the D 2d isomer (1b), the axial ligands form angles of less than 90°with the equatorial plane, indicating the presence of a weak semibridging interaction (Co···C ϭ 2.83 Å and CoϪCoϪC ax ϭ 77.1°), similar to that observed in the optimized isoelectronic anion [Fe 2 (CO) 8 ] 2Ϫ (2.87 Å and 76°for the same parameters), [3] and in [Mn 2 (CO) 8 ] (2.74 Å and 82°). [58] We have found no D 2d structures for carbonyl complexes in the chemical literature, but D 2d structures have been proposed for the isoelectronic compounds [M 2 (PF 3 ) 8 ] (M ϭ [Co 2 (µ-CO) 2 (CO) 6 ] 2.536 193.6 FOHDEL04 [4,5] [Co 2 (µ-CO) 2 (CO) 6 ] 2.539 192.6 [Co 2 (µ-CNXyl) 2 (CNXyl) 6 ] 2.469 198.5 LIDVOJ [40] [Co 2 (µ-CNtBu) 2 (CNtBu) 6 ] 2.457 203.1 TBICCO10 [41] [Co 2 (µ-CO) 2 (CO) 4 (µ-dppa)] 2.457 205.6 PPACCP [42] [Co 2 (µ-CO) 2 (CO) 4 (µ-dmstb)] 2.471 207.8 PAYKUV [43] [Co 2 (µ-CO) 2 (CO) 4 (µ-dmars)] 2.482 200.5 FARSCO10 [44] [Co 2 (µ-CO) 2 (CO) 4 (dppe)] 2.541 188.4 BUVSIU [45] [Co 2 (µ-CO) 2 (CO) 4 (µ-dppbf)] 2.573 195.8 ROBKIC [46] [Co 2 (µ-CO) 2 (CO) 2 (µ-dppa) 2 ] 2.424 209.1 YEZMOF [47] [Co 2 (µ-CO) 2 (CO) 2 (µ-dppm) 2 ] 2.443 212.2 HANSUK [48] [Co 2 (µ-CO) 2 (CO) 2 (µ-deppm)] 2.513 203.7 VAKCEP [49] [Co 2 (µ-CO) 2 (CO) 4 (dppp)] 2.532 193.6 YAWMIS [50] [Co 2 (µ-CO) 2 (CO) 2 (dmpv) 2 ] 2.471 197.9 YIGXUH [51] [Rh 2 (µ-CO) 2 (CO) 3 (PPh 3 ) 3 ] 2.769 193.9 BOPLAT10 [52,53] [Rh 2 (µ-CO) 2 (CO) 2 (dppp) 2 ] 2.709 195.5 CEBBOA [54] [Rh 2 (µ-CO) 2 (CO) 2 [55] [Ir 2 (µ-CNXyl) 2 (CNXyl) 2 (µ-dmpm) 2 2.600 214.6 GEFNAG10 [56,57] [Ir 2 (µ-CNXyl{BH 3 }) 2 (CNXyl) 2 (µ-dmpm) 2 ] 2.589 216.2 KAXNIG [57] [a] Abbreviations: deppm ϭ bis(2-(diethylphosphanyl)ethylphenylphosphanyl)methane; dmars ϭ 1,2-bis(dimethylarsanyl)tetrafluorocyclobutene; dmpv ϭ dimethylphosphanylbenzenevanadium; dmstb ϭ bis(dimethylstibino)methane; dppa ϭ bis(diphenylphosphanyl)amine; dppbf ϭ 4,6-bis(diphenylphosphanyl)dibenzofuran; dppe ϭ 1,2-bis(diphenylphosphanyl)ethane; dppm ϭ bis(diphenylphosphanyl)methane; dppp ϭ 1,3-bis(diphenylphosphanyl)propane; triphos ϭ 1,1,1-tris(diphenylphosphanylmethyl)ethane.…”

Reactions of Bare and Ligated Chromium(I) Ions with Gaseous Arenes. Role of a “Spectator” Aromatic Ring in Chelate Complex Formation

“…In recent years complexes of Cr(0) with [2.2]paracyclophane-type ligands have been actively studied in the condensed phase . It was found possible to introduce a chromium atom into the [2.2]paracyclophane cavity by means of cocondensation techniques, although the resulting (η 12 -[2.2]paracyclophane)chromium(0/I) shows the features of a rather compressed sandwich complex.…”