Boron–boron bond oxidative addition to rhodium(I) and iridium(I) centres

Clegg, William; Lawlor, Fiona J.; Marder, Todd B.; Nguyen, Paul; Norman, Nicholas C.; Orpen, A. Guy; Quayle, Michael J.; Rice, Craig R.; Robins, Edward G.; Scott, A. J.; Souza, Fabio E. S.; Stringer, Graham; Whittell, George R.

doi:10.1039/a705374f

Cited by 51 publications

(30 citation statements)

References 30 publications

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“…Crystals of 7 were obtained by cooling a concentrated hexane solution to À70 8C; the complex crystallizes in the monoclinic space group P2 1 /n. [10] The Ir1 À B1 bond of 7 (1.892 (3) ) is significantly shorter than bonds of known iridium boryl complexes (1.991 (6)-2.093(7) ) [14] and is consistent with a borylene complex. The Ir1ÀB1 bond (1.892 (3) (5) ), [15] but significantly longer than that of terminal borylene complex [(h 5 -C 5 H 5 )Mn(=BCMe 3 )(CO) 2 ] (1.809 (9) ).…”

Section: Holger Braunschweig* Melanie Forster Thomas Kupfer and Famentioning

confidence: 83%

Borylene Transfer under Thermal Conditions for the Synthesis of Rhodium and Iridium Borylene Complexes

et al. 2008

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The recent development of the photochemical transfer of borylene ligands from chromium and tungsten borylene complexes to inorganic, [1] and more recently, organic [2] substrates has shown the "DBX" fragment to be a useful synthon. As is the case for many reactive species, the feisty nature of the difficult-to-generate free borylenes [3] is tempered by coordination to a transition metal, so that their reactivity, which is reminiscent of the neighboring carbene species, [4] can be harnessed in conventional syntheses.In particular, the above-mentioned transfer reaction has proven a boon for the synthesis of borylenes with other metal centers, and has uncovered a surprising synthesis of borirenes from terminal or internal alkynes. However, with the exception of one example, [5] this reaction requires activation by UV light, and is thus limited to photochemically inert substrates. Herein we describe the use of a terminal molybdenum borylene complex [6] which performs this task without irradiation and at ambient temperatures. This new reactivity is borne out in the synthesis of the first terminal borylene complexes of the Group 9 elements rhodium and iridium. These two metals have been the subject of intense investigation regarding their application in catalytic borylation reactions. A variety of boryl complexes have therefore been prepared, [7] however their complexes with lower-coordinate boron have been overlooked owing to the lack of reliable synthetic routes. The complexes presented herein go some way in addressing this deficiency.When the rhodium dicarbonyl complex 2 was added to an equimolar amount of 1 in C 6 D 6 at ambient temperature, multinuclear NMR spectroscopy revealed gradual consumption of the starting materials within 16 h and formation of what appeared to be the terminal borylene species [(h 5 -C 5 H 5 )(OC)Rh = BN(SiMe 3 ) 2 ] (4) with concomitant generation of [Mo(CO) 6 ], as indicated by a resonance at d = 201.49 ppm in the 13 C NMR spectrum for the latter [Eq.(1)]. After workup, 4 was isolated as an analytically pure dark orange oil in 67 % yield.The 11 B{ 1 H} NMR spectrum of 4 features a broad signal at d = 75 ppm (w 1/2 = 309 Hz) which is shifted upfield relative to the signal for 1 (d = 91 ppm), [6] suggesting the formation of a terminal borylene species. [8] The 1 H NMR spectrum shows a singlet for the trimethylsilyl group at d = 0.21 ppm, which is deshielded with respect to that of the molybdenum borylene precursor (d = 0.15 ppm).[6] A single conspicuous band at ñ = 1955 cm À1 in the solution IR spectrum of 4 suggests that a lone CO ligand at rhodium was terminally coordinated. Unfortunately, owing to its oily consistency, it was not possible to obtain single crystals of 4 suitable for X-ray diffraction.Borylene 4 is unstable in solution, which was revealed by 11 B{ 1 H} NMR spectroscopy. The 11 B{ 1 H} NMR spectrum indicated the formation of a new boron-containing product even under mild conditions (hexane at À35 8C). Conversion into the new product was complete after about 15 days, at wh...

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Section: Holger Braunschweig* Melanie Forster Thomas Kupfer and Famentioning

confidence: 83%

Borylene Transfer under Thermal Conditions for the Synthesis of Rhodium and Iridium Borylene Complexes

et al. 2008

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“…This method of preparation has proven useful for the synthesis of a wide range of Rh-bisboryl compounds (Scheme 1). [77][78][79][80] While the addition reactions of aryloxy diborane-(4) compounds are numerous, the addition of alkyloxy based diborane(4) compounds to rhodium centers is much more limited, the only one example known shown in eq 24. 79 Mono-and trisboryl derivatives of rhodium have also been prepared from reactions involving diborane-(4) compounds.…”

Section: Reactions With Diborane(4) Compoundsmentioning

confidence: 98%

“…[77][78][79][80] While the addition reactions of aryloxy diborane-(4) compounds are numerous, the addition of alkyloxy based diborane(4) compounds to rhodium centers is much more limited, the only one example known shown in eq 24. 79 Mono-and trisboryl derivatives of rhodium have also been prepared from reactions involving diborane-(4) compounds. 80 The platinum compound [Pt(PPh 3 ) 2 (BPh 2 ) 2 ] has been reported, 23 although the synthetic details were not described, but as the diborane(4) compound, B 2 -Ph 4 , has not been prepared, it is unlikely that this compound was formed by oxidative addition of a B-B bond.…”

Section: Reactions With Diborane(4) Compoundsmentioning

confidence: 98%

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Transition Metal−Boryl Compounds: Synthesis, Reactivity, and Structure

et al. 1998

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“…Early studies have shown that B 2 cat 2 adds cleanly to [IrCl(PEt 3 ) 3 ] to give bis(boryl) complex [IrCl(Bcat) 2 (PEt 3 ) 2 ] (24) with the concomitant decoordination of PEt 3 (Scheme 30). 115 A single-crystal X-ray diffraction study confirmed that this complex was isomorphous with its rhodium analog. The iridium complex differs in solution from the rhodium species since 116 Theoretical calculations, using the DFT method, examined the iridiumcatalyzed borylation of benzene with diboron source B 2 eg 2 (eg ¼ ethyleneglycolato, dOCH 2 CH 2 Od).…”

Section: Activation By Metal Complexes Of Groupmentioning

confidence: 54%