Structure and bonding of (.mu.-dicarbido)hexa-tert-butoxyditungsten, (tert-BuO)3W.tplbond.CC.tplbond.W(O-tert-Bu)3

Abstract

The molecular structure of (~-B u O )~W~! -C = W ( O -~-B U )~(1) has been determined by single-crystal X-ray crystallography-at -171 "C. The com ound crystallizes with two toluene molecules in the triclinic system, space group P1, with a = 10.926 (7) B, b = 15.706 (12) A, c = 9.674 (6) A, a = 90.99 ( 5 ) O , B = 90.27 (4)O, y = 82.59 (5)O, V = 1646.1 A3, and 2 = 1. The two W(O-t-Bu), groups are arranged in the staggered conformation. The C-C bond length of 1.34 (3) A in the bridge WEC-CEW moiety parallels that in H-C=C-C=C-H (1.384 (2) A). The WEC bond length of 1.819 (16) A is somewhat longer than that in most tungsten alkylidyne complexes. The UV-visible spectrum of 1 in hexane shows five absorptions at 430 (2490 M-' cm-l), 354 (7590 M-' cm-' 1, 294 (11 300 M-' cm-'), 254 (27800 M-' cm-'), and 246 (26800 M-' cm-') nm. Cyclic voltammetry measurements in CH2C12 with n-Bu4NPF6 (n-Bu = CH3CH2CH2CH2) as the supporting electrolyte reveal two irreversible oxidations at 0.362 and 0.816 V vs a saturated calomel electrode (SCE) reference. A MO calculation employing the Fenske-Hall method on the model compound (H0)3WC2W(OH)3 indicates that the C2 ligand is both a strong *-donor and strong ?r-acceptor, which leads to an approach of the limiting valence bond description W&-C=W for the central moiety. A comparison is made with the established chemistry of linear bridged dinitrogen complexes.

Computational analyses of singlet–singlet and singlet–triplet transitions in mononuclear gold‐capped carbon‐rich conjugated complexes

“…Coordination of the heavy metal atoms to the π‐conjugated sp carbon chains forms a family of C n ‐bridged organometallic complexes. As the most fundamental molecular wires, they have received considerable attention in past few years 6–17. It is now established that the presence of a heavy atom in such wirelike compounds will promote spin‐orbit coupling and significantly affect their ground and low‐lying states by an anticipated p π ‐d π bonding interaction between the alkynyl group and metal centers.…”

“…Electronic and geometrical structures of carbon‐rich π‐conjugated organometallic systems in their ground states have been extensively studied by theoretical calculations 6, 9–16, 21. However, knowledge of the singlet and triplet excited states as well as fundamental aspects of the organic triplet emission is still sparse for these metal‐containing conjugated systems.…”

Transition metal alkylidene complexes. Pathways in their formation and tautomerization between bis-alkylidenes and alkyl alkylidynes

“…The NMR spectra of 25 suggest that the two monodentate phosphine ligands take the trans axial positions in the trigonal bipyramid. The crystal structure of an analogous complex, W(CH 2 CMe 3 )(]CHCMe 3 )(^CCMe 3 )(DMPE) (26), was reported by Churchill and Youngs [60]. Since the pathway to this unique class of complexes is not known, we decided to investigate the formation of 10e12.…”

Organometallic Compounds of Chromium, Molybdenum and Tungsten without Carbonyl Ligands

“…The two W(OBu l ) 3 groups adopt a staggered conformation and calculations suggest that the C 2 fragment is both a strong rc-donor and a strong ^-acceptor. 291 Carbyne complexes are the target of numerous other calculations. For instance, extended Huckel methods suggest that in bis(carbyne) species (exemplified by [WH 4 (sCH) 2 ] 4 ) there is a nonbonding 2p combination for both cis and trans isomers.…”