Metal Alkoxides - Models for Metal Oxides. 18. Polynuclear Metal Hydrido Alkoxides. Reactions of W4(H)2(O-i-Pr)14 and W2(H)(O-c-C5H9)7(HNMe2) with Carbon-Carbon, Carbon-Oxygen, and Carbon-Nitrogen Multiple Bonds

Abstract

Reactions between the compounds [W~(H)(O-i-Pr)712 and WZ(H)(O-C-C~H~)~(HNM~~) and olefins, alkynes,allene, 1,3-butadiene, ketones, and nitriles have been studied. Of the olefins, only ethene forms a kinetically persistent compound, and W2(0-c-C5H9)7(q2-C2h)(q1-C2H5) has been fully characterized. Other a-olefins are slowly isomerized to intemal olefins, but, in the presence of added hydrogen, hydrogenolysis to give the alkane is kinetically preferred. Reactions employing allene and/or 1,3-butadiene are more complex as a result of ligand scrambling, and only the compound W~(O-C-C~H~)&-CHZCCHZ) has been fully characterized. With aldehydes and ketones, insertion into the metal hydride generally proceeds to give alkoxide ligands, and the complex W2(0-c-C5H9)8(q2-0-c-c5H8) derived from the reaction involving W:!(H)(O-C-C~H~)~(HNM~~) and cyclopentanone has been fully characterized. With benzophenone, an adduct is formed, which in the solid state and in solution is believed to have a terminal hydride and is formulated as W2(H)(OR)7(q2-OCPh2), an analogue of the W2(q1-C2H5)(q2-C2&) complex. No single product from the reactions between ethyne and a Wz@-H)-containing compound has been fully characterized, but spectroscopic evidence is strongly in favor of a reaction sequence involving (i) ethyne adduct formation, (ii) insertion to form a p-vinyl ligand, and (iii) further addition of ethyne and hydride to give a 2-butenylidene complex W~( O R ) I~( C~H~) . With MeCECMe and [W2(H)(O-i-Pr)7]2, the previously characterized compound W2(0-i-Pr)6@-C4Me4)(q2-c2Me2) is formed with the elimination of i-PrOH and propene. The reactions employing nitriles give products derived from hydride reduction of the coupled nitriles, and the compound W2(0-i-Pr)7@-q1-N,ql-N-NCPhCPhN(H)) has been structurally characterized. Crystal data for W2(0-c-CgH9)7(q2-C2&)(q1-C2H5) at -155 "C: P21/a, a = 20.237(5) A, b = 9.938(5) A, c = 21.660(5) A, p = 113.91(1)", Z = 4. Crystal data for W~( O -C -C~H~)~@ -C H~C C H~) at -171 "C: P21/n, a = 18.070(5) A, b = 24.432(6) A, c = 9.848(2) A, p = 90.19(1)", Z = 4. Crystal data for Wz(0-cC5Hg)8(q2-0-c-C5H8) at -175 "C: P21/c, a = 10.618(1) A, b = 20.824(2) A, c = 22.154(5) A, p = 115.22(1)", Z = 4. Crystal data for W2(H)(O-i-Pr)7(q2-OCPh2) at -172 "C: P21/n, a = 11.899(5) A, b = 19.928(8) A, c = 15.956(7) A, p = 91.61(2)", Z = 4. Crystal data for W2(O-i-Pr)7(p-q1-N,q'-N-NCPhCPhN(H)) at = -171 "C: Pi, a = 18.688(4) A, b = 22.186(5) A, c = 10.368(2) A, a = 94.39(1)", / 3 = 92.42(1)", y = 68.5(1)", Z = 4.

Organometallic Chemistry of [W2(OCH2tBu)8] (M=M): Substrate Uptake and Activation at a Tungsten-Tungsten Double Bond

“…[1] Indeed, in organometallic chemistry the only two systems to have been studied extensively are [Cp* 2 Re 2 (CO) 4 ] by Casey and co-workers [2] and [Os 2 (CO) 8 ]. [3] The latter, though isolable only in a matrix, acts as a template for the binding of alkynes and alkenes.…”

“…Thanks to the elegant work of Norton et al, [3b] it can be construed to exist as [(CO) 4 OsOs(CO) 4 ]. Our recent synthesis [4] of [W 2 (OCH 2 tBu) 8 ] which, though insoluble in noncoordinating hydrocarbon solvents such as hexane and toluene, can be viewed as a d 2 ± d 2 W W-bonded complex having a solid-state structure of one of the types shown in A. [5] This affords us the opportunity to investigate the chemistry of the (WW) 8 template supported by alkoxide ligands, which in turn allows us to compare its reactivity with the [W 2 (OR) 6 ] compounds that have revealed a rich organometallic chemistry, [6] and also with the carbonyl-supported MM bonded systems noted above.…”

“…[W 2 (OCH 2 tBu) 8 (m-C 2 H 2 )] (1): The addition of ethyne to a toluene suspension of the purple [W 2 (OCH 2 tBu) 8 ] gave a red solution of the 1:1 adduct, 1, which was purified by dissolving the crude product in refluxing toluene and cooling to room temperature whereupon red crystals were formed. Compound 1 failed to show any further reactivity in the presence of a 10-fold excess of ethyne.…”

“…[W 2 (OCH 2 tBu) 8 8 ] reacted with one equivalent of ethene to give a green solution of 2. Concentrating the solution and cooling afforded fine microcrystals of 2 which have not thus far proved suitable for an X-ray study.…”

“…The two compounds co-crystallize from hydrocarbon solvents which has impeded their independent characterization. However, the sulfide could be prepared from the reaction between elemental sulfur and [W 2 (OCH 2 -tBu) 8 ] [7] and this reaction will be described in detail elsewhere as part of a separate study of the reactivity of [W 2 (OCH 2 tBu) 8 ] with Group 16 elements. [9] Note, the compound S W(OtBu) 4 has been previously reported.…”