Carsten Kollann

SYNTHESIS AND STRUCTURE OF THE FIRST TERMINAL BORYLENE COMPLEXES

A nearly linear arrangement is observed for the three atoms in the central W-B-N unit of the tungsten complex [(CO)5 WBN(SiMe3 )2 ] (1) in the crystal (W-B-N 177.9°; see picture). This compound along with its Cr analogue represent the first examples of terminal borylene complexes with a two-coordinate metal-bound boron atom. The geometries of the axial and equatorial CO groups in 1 are similar, and thus indicate that there is no trans effect of the borylene ligand.

Synthese und Struktur der ersten terminalen Borylenkomplexe

Nahezu linear sind die drei Atome der zentralen W-B-N-Einheit des Wolframkomplexes [(CO)5WBN(SiMe3)2] 1 im Kristall angeordnet (Bindungswinkel 177.9°; siehe Bild). Diese Verbindung und ihr Cr-Analogon sind die ersten terminalen Borylenkomplexe mit zweifach koordiniertem Bor. Die ahnliche Geometrie des axialen und der aquatorialen CO-Liganden in 1 spricht gegen einen trans-Effekt des Borylenliganden.

[(OC)5Cr=BSi(SiMe3)3]: A Terminal Borylene Complex with an Electronically Unsaturated Boron Atom

An extremely low-field shifted 11 B NMR signal at δ=204.3 and a very short Cr-B distance of 187.8 pm characterize the title compound [(OC)5 Cr=B-Si(SiMe3 )3 ], which is the first borylene complex in which the boron atom is both coordinatively and electronically unsaturated.

BORYL- AND BRIDGING BORYLENEIRON COMPLEXES FROM AMINODICHLOROBORANES

Depending on the nature of the amino group bound to the boron atom, the reactions of various aminodichloroboranes R2NBCl2 with Na[(η5-C5R′5)Fe(CO)2] yield either boryl or bridging borylene complexes of iron. The compounds [(C5R′5)(CO)2Fe{BCl(NR2)}] (1a, C5R′5 = C5H5, R = Me; 1b, C5R′5 = C5H4Me, R = Me; 1c, C5R′5 = C5Me5, R = Me) and [(η-BNR2)(μ-CO){(C5R′5)Fe(CO)}2] (2a, C5R′5 = C5H5, R = SiMe3; 2b, C5R′5 = C5H4Me, R = SiMe3) were isolated as orange (1a−c) or red (2a, b) crystalline solids, and characterized by multinuclear NMR methods and IR spectroscopy. The structures of 1c and 2b in the crystalline state were determined by single-crystal X-ray studies.

Boryl and Bridged Borylene Complexes of Iron and Ruthenium

The reactivity of aminodihaloboranes R2NBX2 (R = Me, SiMe3; × = Cl, Br) towards transition metal complexes of the type Na[(η5-C5R′5)M(CO)2)] (M = Fe, Ru; R′ = H, Me) was investigated. In the case of Me2NBBr2 and M = Fe the borylcomplexes [(η5-C5R′5)(CO)2Fe{BBr(NMe2)}] (C5R′5 = C5H59a; C5R′5 = C5H4Me 9b; C5R′5 = C5Me510) were obtained. The compounds 9aand 9bwere formed together with the corresponding bridged borylene complexes [μ-BNMe2(μ-CO){(η5-C5R′5)Fe(CO)}2] (C5R′5 = C5H511a; C5R′5 = C5H4Me 11b) in a 1:1 ratio, the latter, however, could be isolated from these mixtures as pure materials. In addition the novel boryl and borylene ruthenium complexes [(η5-C5H5)(CO)2Ru{BX(NMe2)}] (X = Cl 12a; × = Br 12b), [(η5-C5H5)(CO)2Ru{BCl{NSiMe3{BClN(SiMe3)2}}}] (13) and [μ-BN(SiMe3)2(μ-CO){(η5-C5H5)Ru(CO)}2] (14) were obtained by similar methods. All compounds were characterized by multinuclear NMR and IR spectroscopy. The structure of 13 in the solid state was determined by a single-crystal X-ray diffraction study.

Reaktionen von [(η5-C5R5)2WH2] mit Boranen / Reactions of [(η5-C5R5)2WH2] with Boranes

Reactions of [Cp2WH2] with B(C6F5)3 and Me2NB(CF3)2, respectively, leads to the formation of the zwitterions [CpWH3{η5-C5H4B(C6F5)3}] (1) and [CpWH2{η5-C5H4B(NHMe2)(CF3)2}] (2). [Cp*2WH2] reacts with B(C6F5)3 and tBuBCl2 to give the saltlike compounds [Cp*2WH3][B(C6F5)4] (3) and [Cp*2WH3][tBuBCl3] (4).

The first silyl- and germylboryl complexes: synthesis from novel (dichloro)silyl- and (dichloro)germylboranes, structure and reactivity

A series of silyl- and germyl(dichloro)boranes Cl2B–ER3 (5, ER3 n= Si(SiMe3)3; 6, ER3 n= Ge(SiMe3)3; 7, ER3 n= Si(SiMe3)2–Si(SiMe3)3; 8, ER3 n= SiPh3) was obtained in good yields from the corresponding bis(dimethylamino)boranes (Me2N)2B–ER3 (1, ER3 n= Si(SiMe3)3; 2, ER3 n= Ge(SiMe3)3; 3, ER3 n= Si(SiMe3)2–Si(SiMe3)3; 4, ER3 n= SiPh3) upon reaction with BCl3, and fully characterised in solution. These compounds proved to be versatile starting materials for the synthesis of the first silyl- and germylboryl complexes by salt elimination reactions starting from anionic transition metal complexes of the type Na[(η5-C5R5)Fe(CO)2] and K[(η5-C5R5)Mn(H)(CO)2]. The novel iron and manganese boryl complexes [(η5-C5R4R′)(OC)2Fe–B(Cl)Si(SiMe3)3] (9a, R = R′ n= H; 9b, R = H, R′ n= Me; 9c, R = R′ n= Me), [(η5-C5H5)(OC)2Fe–B(Cl)Ge(SiMe3)3] n(9d), [(η5-C5H5)(OC)2Fe–B(Cl)Si(SiMe3)2Si(SiMe3)3] (9e), [(η5-C5H4Me)(OC)2(H)Mn–B(Cl)Si(SiMe3)3] (10a) and [(η5-C5H4Me)(OC)2(H)Mn–B(Cl)Ge(SiMe3)3] (10b) were obtained in yields between 35 and 70%, fully characterised in solution and in the case of 9a, d, and 10a also in the crystalline state. They are all characterised by metal–boron σ-bonds without indication of any metal-to-boron π-backdonation. There is, however, spectroscopical nand structural evidence for the presence of a Mn–H–B bridge in the case of the manganese complexes 10a, b. The first transhalogenation of a metal coordinated boryl ligand was achieved by reaction of 9a with TlF affording the fluoroboryl complex [(η5-C5H5)(OC)2Fe–B(F)Si(SiMe3)3] (11), which was characterised in solution and in the solid state.