Synthesis and reactivity of the metal-substituted borane (CO)4CoBH2.cntdot.THF. Preparation of the ambiphilic clusters (CO)9Co3C(CH2)nOH (n = 4,5)

Abstract

The reaction C O~( C O )~ + 2BH3.THF -2(CO),CoBH2.THF (I) + H2 has been demonstrated to occur cleanly at -15 "C in THF. I has been characterized by low-temperature I'B NMR and infrared spectroscopies as well as classical chemical analysis. The formation of I bears a remarkable similarity to that of (CO),CoSiR,. Displacement of the bound THF of I occurs with Lewis bases, and the Lewis acidity of I relative to that of BH3.THF for SMe, has been estimated. Displacement of [Co(CO),]-from I occurs easily; e.g., reaction with PhMgBr yields PhBH,. I readily accepts hydride from [HFe2(CO)B]-, losing [Co(CO)J but reduces the CO ligands of hydride-free metal carbonylate anions. I is a very active reducing agent and above 10 "C cleaves THF and condenses with hydrocarbyl and metal fragments to yield a mixture of clusters including an unusual tailed cluster (CO)&o3C(CH2),OH ( n = 4,5) (11). A deuterium labeling experiment showed that four of the n carbons in the hydrocarbyl chain of I1 arise from THF. The results of an X-ray diffraction study suggest association of I1 in the solid state. [Crystals of I1 (the ratio of I1 with n = 5 / n = 4 is 4) form in the space group R3 with unit cell parameters a = 34.409 (15) A, 6 = 34.398 (21) A, c = 8.575 (5) A; a = 0 = 90°, y = 120°, V = 8789.8 A', and Z = 18. Solution was by direct methods, and all atoms were refined to R, = 0.077 and R2 = 0.096 for 1443 independent reflections (F, > 3u(FO)). Because of the disorder caused by the cwrystallization of species with different chain lengths, the last two atoms at the OH end of the chain could not be fully defined.] Association of I1 in solution is shown by a IH NMR study, thereby demonstrating that I1 behaves as an ambiphilic cluster.

Base‐Stabilized Boryl and Cationic Haloborylene Complexes of Iron

“…Due to the fact that sp 3 -hybridized borane IMe·BH 3 is isoelectronic with alkanes, its BÀH activation by s-bond metathesis and concomitant formation of a metalboron bond is remarkable and only rarely described in literature. [6,11] The determined molecular structure of 2 in the solid state is in full agreement with the obtained spectroscopic data (Figure 1).…”

“…The signals obtained by NMR spectroscopy in solution ( 1 H, 11 B, and 13 C{ 1 H}) were assigned, and the boron-bound protons give rise to a broad quartet signal at d = 2.15 ppm in the 1 H NMR spectrum. The measured coupling constant 1 J HB = 108 Hz also can be found in the 11 B NMR spectrum, which shows a triplet signal at d = À27.9 ppm. This value is about 10 ppm higher (lower field) than that of precursor 1 and comparable to that of [(h 5 -C 5 Me 5 )Fe(CO) 2 A C H T U N G T R E N N U N G (BH 2 ·PMe 3 )] (d = À25.1).…”

“…For simplicity reasons, only one of these molecules is depicted and discussed. Selected bond lengths [] and angles [8] for 4: BÀFe 2.121 (2), FeÀC1 1.739 (2), FeÀC2 1.744 (2), C1ÀO1 1.156 (2), C2ÀO2 1.155 (2), BÀN 1.621 (2), BÀCl1 1.884 (2), BÀCl2 1.885 (2); Fe-B-N 114.33 (11). Selected bond lengths [] and angles [8] for 5: BÀFe 2.102 (2), FeÀC1 1.738 (2), FeÀC2 1.750 (2), C1ÀO1 1.163 (2), C2À O2 1.154 (2), BÀP 1.989 (2), BÀCl1 1.920 (2), BÀCl2 1.903 (2); Fe-B-P 121.20 (9).…”

Transition‐Metal Complexes of Boron—New Insights and Novel Coordination Modes

“…Surprisingly, considering the known tendency of boranes BR 3 to form adducts with Lewis bases, formation of analogous Lewis acid–base adducts by preformed boryl complexes was first reported in 2004. The first reports on base‐stabilized boryl compounds date back to 1990,40 and used borane adducts BH n X m L or borates [BH 4 ] − as boron sources (Scheme ).…”

Molybdenum complexes bearing a diaminosubstituted-phosphiteboryl ligand: Syntheses, structures, and reactivity involving the Mo–B, B–P, and B–H activation

“…transition metal complexes have been reported for tri-coordinate boranes [2,3]. In contrast, little is known of B-H bond activation of tetra-coordinate (sp 3 -type) boranes such as BH 3 AE PR 3 [4,5]. Shimoi 3 Me and its derivatives in the presence of several phosphorus compounds, such as diaminosubstituted-phosphiteborane, BH 3 P(NMeCH 2 ) 2 (OMe) (1), produced phosphiteboryl Mo complexes, such as Cp * Mo(CO) 3 BH 2 {P(NMeCH 2 ) 2 -(OMe)} (2).…”