The platinum(0) monocarbonyl complex, [(Cy(3)P)(2)Pt(CO)], was synthesized by reaction of [(Cy(3)P)(2)Pt] with [(η(5)-C(5)Me(5))Ir(CO)(2)] and subsequent irradiation. X-ray structure analysis was performed and represents the first structural evidence of a platinum(0) monocarbonyl complex bearing two free phosphine ligands. Its corresponding dicarbonyl complex [(Cy(3)P)(2)Pt(CO)(2)] was synthesized by treatment of [(Cy(3)P)(2)Pt] with CO at -40 °C and confirmed by X-ray structure analysis.
Wegen ihrer Verwandtschaft [1][2][3][4] zu Carbonyl-und Carbenkomplexen sowie ihres Potenzials, Borylene BÀR für organische Reaktionen zu liefern, [5] haben Übergangsmetall-borylenkomplexe großes Interesse geweckt. Trotz jüngster Erfolge bei der Verwirklichung neuartiger Koordinationsmodi in Metallborylenkomplexen [6,7] und Borylen-Heterozweikernkomplexen [8,9] sind die Möglichkeiten insofern immer noch stark eingeschränkt, als nur Kombinationen zwischen jeweils einem Borylenliganden und einem bzw. zwei Metallzentren bekannt sind. Vor dem Hintergrund der Strukturverwandtschaft zwischen Borylen-und Carbonylkomplexen überrascht dies, besonders wenn man die Vielfalt mehrkerniger Carbonylkomplexe berücksichtigt. [10] Der Hauptgrund dafür scheint in der guten Verfügbarkeit des metastabilen CO zu liegen, das in unterschiedlichen stö-chiometrischen Verhältnissen mit Metallkomplex-Vorstufen zu mehrkernigen Carbonylverbindungen komplexer Struktur reagiert. ¾hnliches gilt für die höheren Homologen der Borylene (speziell Cp*Ga und Cp*In), die ebenfalls für die Synthese ein-oder mehrkerniger Komplexe zur Verfügung stehen.[11] Da die Borylene hoch reaktive Spezies sind, können sie jedoch nicht unter Normalbedingungen gehandhabt werden, [3] sondern sie müssen zunächst in der Koordinationssphäre eines Übergangsmetallatoms erzeugt werden. Dazu hatten sich zunächst Salzelimierungsreaktionen zwischen anionischen Carbonylaten und Halogenboranen bewährt, welche die ersten verbrückten und terminalen Borylenkomplexe lieferten. [12,13] Diese Methode könnte jedoch bereits an ihre Grenzen gestoßen sein, denn sie ist auf wenige spezielle Kombinationen von Übergangs-metallen und Boranen beschränkt. [14][15][16] In jüngerer Zeit konnten wir zeigen, dass der photochemisch induzierte Borylentransfer eine wertvolle Methode für die Synthese von Borylenkomplexen darstellt, die durch Salzeliminierung nicht zugänglich sind. [17,18] Darüber hinaus ermöglicht diese Vorgehensweise die Übertragung der Boryleneinheit auf organische Substrate.[
Free borylenes are elusive, highly reactive species that are not accessible under ambient conditions but can be generated and effectively stabilized in the coordination sphere of transition metals, thus yielding a variety of borylene complexes.[1] The close relationship of this class of compounds with ubiquitous transition-metal carbonyl complexes is reflected by the fact that BR ligands adopt the same bonding pattern (i.e. ligand! metal s and metal!ligand p bonding) and coordination modes (terminal, [2] doubly [3] or triply bridging, [4] and semibridging [5] ) as their CO counterparts. Of particular interest are terminal borylene complexes, since very recently it was demonstrated that such compounds serve as potential sources for elusive BR species, thus allowing for unprecedented borylene-based functionalization of organic substrates. [6] Access to these compounds is commonly achieved by salt elimination reactions between dianionic metal carbonylates and suitable dihaloboranes, or in the case of cationic borylene complexes, by halide abstraction from appropriate haloboryl precursors. Both methods, however, are severely limited in scope and have only been successfully applied to Group 6 metals, [7] iron, [8] and most recently, platinum.[9]In order to provide more general access to terminal borylene complexes, we have started to investigate intermetal borylene transfer [10] and succeded in the isolation of unprecedented mononuclear vanadium [11] and tetranuclear rhodium [12] borylene species, which cannot be obtained by the aforementioned conventional syntheses. Herein, we describe the stepwise borylene transfer from tungsten to cobalt, which proceeds via an unprecedented heterodinuclear intermediate to furnish the first cobalt borylene complexes.Photolysis H} NMR spectrum of 3 displays a broad singlet at d = 103 ppm (w 1/2 = 488 Hz), which is shifted downfield with respect to that of the starting material 1 (d = 87 ppm), [7a] as expected for the formation of a bridged borylene complex.[1b] The 1 H NMR spectrum shows one new singlet for the trimethylsilyl group at d = 0.22 ppm, which is deshielded in comparison to that of the borylene precursor 1 (d = 0.12 ppm).[7a]The proposed constitution of 3 was confirmed by singlecrystal X-ray diffraction (Figure 1).[13] Crystals of 3 were obtained by cooling a concentrated hexane solution to À35 8C; the complex crystallizes in the monoclinic space group P2 1 /n.In the solid state, the {W(CO) 5 } and {(h 5 -C 5 H 5 )Co(CO)} fragments are linked by a bridging borylene ligand BN-(SiMe 3 ) 2 . The W1 À B1 bond (2.434(3) ) is considerably elongated in comparison to that of the corresponding terminal borylene complex 1 (2.151(7) ), [7a] in agreement with the increased coordination number of the boron center.
All good things come in fours: Thermal metal–metal borylene transfer from the terminal borylene complexes [(OC)5MBN(SiMe3)2] (M=Cr, W) leads to the new tetranuclear rhodium complex [Rh4{μ‐BN(SiMe3)2}2(μ‐Cl)4(μ‐CO)(CO)4] (see structure), which is the first doubly borylene‐bridged transition‐metal complex. In the solid state, the tetranuclear units aggregate (dashed lines), giving a rare example of a neutral chain of rhodium atoms.
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