Synthesis of Os₃W alkylidyne and alkylidene clusters by solid-state pyrolysis; direct C–O bond cleavage of co-ordinated ketenyl ligand

Abstract

The heterometallic tetranuclear ketenyl compound [Os,(CO),,(p-H){C(O)CH,W(CO),(q-C,Me,)}] 1 possessing a pendant W(q-C,Me,) (CO), substituent is prepared by condensation of [Os,(CO),,-(NCMe),] with the aldehyde complex [W(q-C,Me,)(CO),(CH,CHO)].Pyrolysis of 1 in the solid state at 185 "C afforded four tetrahedral compounds [WOs,(q-C,Me,) (CO),(p-0) (p,-CMe)] 2, [WOs,(q-C,Me,) (CO),(p-0) (p-H) (p-CHMe) J 5. [WOs,(q-C,Me,) (CO),,(p,-CMe)] 3 and [WOs,(q-C,Me,) -(CO),,(p,-CH)] 4, demonstrating a unique example of C-0 bond scission for the ligated ketene fragment. Since treatment of 2 with H, in toluene also afforded 5 in moderate yield, it is highly probable that the latter is produced via reaction with trace amounts of H, generated from the decomposition of 1. The molecular structures of 2 and 4 have been determined by single-crystal X-ray analysis.The chemistry of organic ketene molecules as well as of organometallic ketenyl complexes has been investigated extensively, ' since ketenes are important reagents in organic synthesis and ligated ketenes can serve as intermediates in hydrocarbon chain growth in CO-reduction reactions2 Diand tri-nuclear ketene complexes have been synthesised by coupling of methylene and carbon monoxide: several research groups have demonstrated that ligated methylene can link with CO to give ketene, and that the resulting ketene fragments undergo isomerization to afford a formylmethylene ligand4 and dehydration to afford a ligated acetylide fragment., Further treatment of ketene complexes with alcohol led to formation of acetate,6 while reaction with dihydrogen gives aldehydes,' reactions with electrophiles, such as H + or Me', give acyl and vinyl ligands,8 and with diazomethane affords an oxalyl ligand.9In this paper, we describe the preparation of a ketenyl comreaction of the aldehyde complex w ( q -C ,Me,)(CO),(CH,-CHO)] with [Os,(CO),,(NCMe),]. As one of our research goals is to generate heterometallic clusters, ' O we studied the solid-state pyrolysis of 1 in an attempt to generate direct W-Os bonding between the Os, triangle and the W(q-C,Me,)(CO), fragment through thermally induced CO elimination. Several tetrahedral clusters containing 0x0, alkylidyne and alkylidene functional groups were isolated, producing strong evidence for cleavage of the ketenyl C-O bond. Related C-O bond scission has been observed for the triply bridging acyl ligand of the rhomboidalclusters [MOs,(q-C,Me,)(CO) {p3-q 2-C(0)CH2-plex [Os3(CO)io(p-H){ C(~)CH~W(C~)~(~-C,M~S)}~ 1 via C&Me-p)] (M = W or Mo). '' ExperimentalGeneral.-Infrared spectra were recorded on a Bomen M-100 FT-IR spectrometer, 'H and 13C NMR spectra on a Bruker AM-400, Varian Gemini-300 or Varian Unity-400 instrument. Chemical shifts are quoted with respect to internal SiMe, ('H and 13C). Mass spectra were obtained on a JEOL-HXllO instrument operating in fast atom bombardment (FAB) mode. All reactions were performed under a nitrogen atmosphere using deoxygenated solvents dried with an appropriate reagent.

Reversible C−C Bond Cleavage and Interconversion of the Resulting Hydrocarbyl Ligands on Butterfly Frameworks Derived from Acetylide Complexes Cp*WOs3(μ4-CCR)(CO)11(R = Ph,nBu, CH2OMe, CH2OPh)

“…Upon heatng the sample up to 294 K, the C H 2 C H 2 OMe multiplets in the 1 H NMR spectrum coalesced into two featureless signals centered at δ 4.04 and 3.56, while the W−CO signal merged into the baseline in the 13 C NMR spectrum, and the Os−CO signals turned into two broad signals at δ 181.0 and 179.5 simultaneously. Based on these variable-temperature NMR data and the solid-state structures established, ,, we propose that the observed dynamics in solution is due to the exchange of the bridging and the terminal CO ligands of the W atom, which generated a time-averaged mirror plane bisecting the WOs 3 tetrahedral framework.

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“…Treatment of 11 under CO afforded the alkylidyne cluster 12 in 90% yield. The identification of 12 is mainly provided by the IR ν(CO) data, which resemble those of the numerous documented complexes of formulation LWM 3 (μ-CR)(CO) 11 (L = Cp, C 5 Me 5 ; M = Os, Ru; R = H, Me, C 5 H 11 , Ph, OMe). ,, The 13 C NMR spectrum at 220 K showed two distinct W−CO signals at δ 223.9 and 206.6 and four Os−CO signals at δ 187.1, 183.4, 180.7, and 176.0 in the ratio of 1:1:6:1. The 1 H NMR spectrum exhibited four well-resolved multiplets at δ 4.06, 3.91, 3.55, and 3.46 (AA‘BB‘ spin system) at the same temperature, due to the methylene protons of the CC H 2 C H 2 OMe fragment.…”

Syntheses and Reactivity of Heterometallic Oxo−Acetylide Cluster Compounds. Skeletal Rearrangement and Conversion of Acetylide to Alkenyl, Alkylidene, and Allenyl Ligands on a WRe2 Framework

“…The oxo ligand has changed to an asymmetric WO→Re bridging mode with distances W−O(7) = 1.765(6) Å and Re(1)−O(7) = 2.286(5) Å. These distances are similar to those in the WRu 4 cluster Cp*W(O) 2 Ru 4 (μ 4 -PPh)(CCPh)(CO) 10 and the trinuclear cluster Cp 2 W 2 Re(μ-Br)(μ-O)(μ-CTol) 2 (CO) 3 and are also related to the WO→Os mode of cluster compounds having the WOs 3 (μ-O) core arrangement 3 Molecular structure of Cp*WRe 2 (μ-O)(μ-H) 2 (CCPh)(CO) 6 ( 5a ) and selected bond lengths (Å) and angles (deg): Re(1)−Re(2) = 3.0412(5), Re(1)−W = 2.8652(6), Re(2)−W = 2.9918(6), W−O(7) = 1.765(6), Re(1)−O(7) = 2.286(5), W−C(7) = 2.189(8), Re(1)−C(7) = 2.370(8), Re(2)−C(7) = 2.028(7), W−C(8) = 2.118(8), Re(1)−C(8) = 2.496(8), C(7)−C(8) = 1.34(1), W−H(1) = 1.78(6), Re(2)−H(1) = 1.86(6), Re(1)−H(2) = 1.78(7), Re(2)−H(2) = 2.03(8), W−O(7)−Re(1) = 89.1(2), Re(2)−C(7)−C(8) = 157.2(7), C(7)−C(8)−C(9) = 138.7(8). …”

Synthesis, Characterization, and Photophysical Properties of Os(II) Diimine Complexes [Os(N∧N)(CO)2I2] (N∧N = Bipyridine, Phenanthroline, and Pyridyl Benzoxazole)

“…After the reaction was completed, the tube was opened, and the contents were extracted with a minimal amount of CH 2 Cl 2 ; the solution was then subjected to column chromatography resulting in the isolation of pure Os products. This solid-state pyrolysis technique appears to be very simple and has the advantage of allowing us to conduct the reactions at higher temperatures free from the interference of organic solvents . In contrast, the second-row analogues, such as [Ru(bpy)(CO) 2 Cl 2 ], were prepared from [Ru(CO) 3 Cl 2 ] 2 or the oligomeric reagent [Ru(CO) 2 Cl 2 ] n with a diimine ligand, such as 2,2‘-bipyridine (bpy), in refluxing alcohol or THF solutions .…”