“…This aspect of metallaborane chemistry is poorly evidenced in the literature simply because the synthetic chemistry is still in an emerging state. − For monometallic compounds there are several systematic methods of value, but for multimetallic compounds there are very few indeed . Yet when a metallaborane can be made in good yield from easily accessible starting materials, a study of its reactivity reveals a novel and interesting chemistry that parallels, but differs from, that of related organometallic compounds, e.g., the beautiful development of the reactivity of H 3 Os 3 (CO) 9 BCO with connections to the isoelectronic H 2 Os 3 (CO) 9 CCO organometallic compound. − Consequently, there is considerable merit in seeking new routes and developing the reaction chemistry of the compounds that result from successful efforts.…”
The reactions of nido-2,4-(Cp*Co) 2 B 3 H 7 , 1, Cp* ) (η 5 -C 5 Me 5 ), with Fe 2 (CO) 9 and Co 2 (CO) 8 generate seven skeletal electron pair (sep) nido-1-{Cp*Co}-2-((CO) 3 Fe)B 3 H 7 , 2, by metal fragment substitution and seven sep arachno-Cp*(CO)CoB 3 H 7 , 3, by metal fragment degradation. Both compounds are characterized spectroscopically in solution and with singlecrystal X-ray diffraction in the solid state. On the basis of the results and related chemistry, the suggested reaction pathway involves M(CO) 4 , M ) Fe and Co, coordination to a Co-H-B edge of 1 followed by loss of Cp*Co(CO) which leads to 2. We postulate that the cobalt analogue of 2, which would be an odd-electron species, readily loses a cobalt carbonyl fragment to form 3. metal fragment substitution in one case and metal fragment loss in the other. The former has been observed in related organometallic clusters 23 as well as metallaborane chemistry. 24 The latter constitutes a new route to so-called "borallyl" complexes previously prepared from [B 3 H 8 ]and mononuclear metal complexes of Ir, 25,26 Pd,27,28 and Pt 29-31 with phosphine ancillary ligands. Here a first-row transition-metal analogue is synthesized by building up a B 3 H 7 fragment on a dicobalt framework followed by removal of one metal fragment. A previous attempt to make a cobalt borallyl complex by reacting (PPh 3 ) 2 CoCl 2 with [B 3 H 8 ]led only to the phosphine adduct B 3 H 7 PPh 3 . 25
Experimental SectionGeneral. All operations were conducted under a dinitrogen atmosphere using standard Schlenk techniques. 32 Solvents were distilled before use under N2 as follows: sodium benzophenone ketyl for hexane, diethyl ether, and tetrahydrofuran. The starting material nido-2,4-(Cp*Co)2B3H7, 1, was prepared according to published procedures. 16 Fe2(CO)9 (Aldrich) and Co2(CO)8 (Strem) were used as received. NMR spectra were recorded on a 300 or 500 MHz Varian FT-NMR spectrometer. The solvent proton signal was used as a reference for 1 H NMR (δ, ppm, benzene, 7.15), while a sealed tube containing [Et4N][B3H8] in acetone-d6 (-29.7 ppm) was used as the external reference for 11 B NMR. Infrared spectra were obtained on a Nicolet 205 FT-IR spectrometer. Mass spectra were obtained on a Finnigan MAT model 8400 mass spectrometer with EI mode. Perfluorokersene was used as the standard for the high-resolution EI mass spectra. Elemental analysis was performed by M-H-W Laboratories, Phoenix, AZ.
nido-1-(Cp*Co)-2-{(CO)3Fe}B3H7, 2.In a 200 mL Schlenk tube, nido-2,4-(Cp*Co)2B3H7, 1 (0.40 g, 0.94 m.mol), and Fe2-(CO)9 (0.43 g, 1.18 mmol) were loaded. A 15 mL amount of freshly distilled toluene was slowly added to the mixture by syringe. The reaction mixture was stirred at ca. 50°C for 6 h. During this period, a black solid and a dark brown solution were observed to form. The toluene was then removed under vacuum, and the resulting residue was extracted with hexane and filtered through Celite. Low-temperature column chromatography (-40°C) was performed. Elution with hexane gave a brown solution o...
“…Crystallographic data have been deposited with the Cambridge Crystallographic Data Center as supplementary publication no. CCDC 1574739 (2), 1574738 (3), 1574737 (4) and 1574736 (5). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif.…”
Section: X-ray Structure Determinationmentioning
confidence: 99%
“…Discrete and extended transition metal clusters that contain interstitial atoms form an interesting class of compounds due to their combined fundamental aspects as well as applied research [1][2][3][4][5]. As a result, compounds containing main group elements such as carbon, nitrogen and phosphorous at the interstitial environment have been well documented in the literature [6][7][8][9][10][11][12][13][14][15][16][17][18].…”
A number of heterometallic boride clusters have been synthesized and structurally characterized using various spectroscopic and crystallographic analyses. Thermolysis of [Ru3(CO)12] with [Cp*WH3(B4H8)] (1) yielded [{Cp*W(CO)2}2(μ4-B){Ru(CO)3}2(μ-H)] (2), [{Cp*W(CO)2}2(μ5-B){Ru(CO)3}2{Ru(CO)2}(μ-H)] (3), [{Cp*W(CO)2}(μ5-B){Ru(CO)3}4] (4) and a ditungstaborane cluster [(Cp*W)2B4H8Ru(CO)3] (5) (Cp*=η5-C5Me5). Compound2contains 62 cluster valence-electrons, in which the boron atom occupies the semi-interstitial position of a M4-butterfly core, composed of two tungsten and two ruthenium atoms. Compounds3and4can be described as hetero-metallic boride clusters that contain 74-cluster valence electrons (cve), in which the boron atom is at the basal position of the M5-square pyramidal geometry. Cluster5is analogous to known [(Cp*W)2B5H9] where one of the BH vertices has been replaced by isolobal {Ru(CO)3} fragment. Computational studies with density functional theory (DFT) methods at the B3LYP level have been used to analyze the bonding of the synthesized molecules. The optimized geometries and computed11B NMR chemical shifts satisfactorily corroborate with the experimental data. All the compounds have been characterized by mass spectrometry, IR,1H,11B and13C NMR spectroscopy, and the structural architectures were unequivocally established by crystallographic analyses of clusters2–5.
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