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)5MBN(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.

The incorporation of subvalent Group 13 ligands into the coordination sphere of transition metals has always been a challenging task, particularly in the formation of homoleptic complexes. Although metastable or sterically protected subvalent E I (E = Al, Ga, In) precursors have become accessible during the last few decades, [1] for example, E I halides, [1, 2] [{Cp*E} n ] (Cp* = h 5 -C 5 Me 5 ), [1, 3] and [{EC(SiMe 3 ) 3 } n ], [1, 4] stable and isolable boron congeners have still not been prepared. For this reason, only homoleptic transition-metal complexes with Al-, Ga-, and In-based ligands have so far been realized, for example, mononuclear [Ni(ECp*) 4 ] (A; E = Al, Ga) [5,6] and [Ni{EC(SiMe 3 ) 3 } 4 ] (B; E = Ga, In), [7,8] as well as numerous heteroleptic examples with two or more E I ligands. [9] The corresponding subvalent boron ligands, that is, borylenes, have only been generated directly in the coordination sphere of transition metals [10] to form species such as [(OC) 5 M=BN(SiMe 3 ) 2 ] (C; M = Cr, Mo, W).[11] To date, both mononuclear borylene complexes containing more than one borylene substituent as well as homoleptic borylene species have continuously resisted isolation. Nonetheless, borylene complexes have sparked increasing interest in fundamental organometallic research because of their close relationship with important organometallic compounds such as carbene, carbyne, and vinylidene complexes, and the similarity of the bonding properties of borylene and carbonyl ligands. Numerous experimental and computational studies have previously examined these bonding properties in detail.[10] It was thus shown that BR has stronger s-donor and p-acceptor properties than CO, which makes the M À BR bond even more stable with respect to homolytic dissociation than the M À CO bond, but in turn it is kinetically labile due to the high polarity. Getting back to the series of related ligands mentioned above, the predominance of the CO and carbene ligands in organometallic chemistry is also manifested by the fact that homoleptic complexes have only been accessible with these two ligands. By contrast, the incorporation of two borylene or carbyne ligands into a mononuclear transition-metal complex has always proven problematic. While in the former case a suitable synthetic approach is still lacking, [12] the synthesis of bis(carbyne) species is further hampered by reductive coupling to form acetylenes, particularly with alkyl-substituted carbynes.[13] It has not yet been elucidated whether bis-(borylene) complexes are resistant towards reductive coupling. In any case, it would require the availability of experimental data before this question could be clarified. We have been studying borylene complexes for more than a decade now, but all our efforts to synthesize a complex with more than one terminal borylene have so far failed.Herein, we describe the successful generation and isolation of a long-sought after mononuclear, terminal bis-(borylene) complex derived from the [Cp*Ir] half-sandwich fragment,...

Schritt für Schritt: Die stufenweise Übertragung des Borylenliganden BN(SiMe3)2 von [(OC)5WBN(SiMe3)2] auf [(η5−C5H5)Co(CO)2] führt zu den ersten ein‐ und zweikernigen Cobaltborylenverbindungen. Dieser Intermetallborylentransfer erfolgt als assoziativer Prozess über einen Heterozweikernkomplex (siehe Struktur), ohne dass ein freies Borylen als Zwischenstufe auftritt.

Herein we report on the synthesis and structural characterization of a representative range of novel heterodinuclear bridging rhodium and iridium borylene complexes. The iridium borylene complexes feature an unusual coordination mode of the borylene ligand. Furthermore, the first instance of a heterodinuclear-bridged borylene compound containing a chromium atom in the three-membered ring is reported.

Bei Raumtemperatur liefert der Borylentransfer von [(OC)5MoBN(SiMe3)2] auf [(η5‐C5R5)M(CO)2] (M=Rh, R=H; M=Ir, R=Me) terminale Borylenkomplexe von Rhodium und Iridium (siehe Schema). Der Iridiumkomplex 1 konnte röntgenstrukturanalytisch charakterisiert werden.