Preparation and Structural Characterization of Transition Metal Complexes Featuring the Ferrocenyl(bromo)boryl Ligand

Abstract

Transition metal complexes that feature the ferrocenyl(bromo)boryl ligand, -B(Fc)Br, were prepared utilizing salt-elimination and B-Br bond oxidative addition strategies. The stabilizing interaction that causes bending of the boron atom toward the ferrocenyl iron center in the FcBBr 2 precursor (1) weakens upon coordination of boron to the [(η 5 -C 5 R 5 )-(OC) 2 Fe] and trans-[(Cy 3 P) 2 PtBr] fragments. The efficient π-back-bonding capability of the latter is reflected in the absence of any Fe-B interaction in crystalline trans-[(Cy 3 P) 2 Pt-(Br){B(Fc)Br}] (7), the first platinum haloboryl complex featuring a non-heteroatom-stabilized boryl ligand to be fully characterized and structurally authenticated. In the half-sandwich complexes [(η 5 -C 5 R 5 )(OC) 2 Fe{B(Fc)Br}] (R ) H, 2; R ) Me, 3) different relative orientations of the [(η 5 -C 5 R 5 )(OC) 2 Fe] and -B(Fc)Br groups are accompanied by different degrees of bending within the boryl ligand. The sensitivity of this parameter to the electronic environment at boron offers an indirect qualitative estimation of the π-bonding component of the TM-B bond. † Dedicated to Prof. Dr. Johann Weis on the occasion of his 60th birthday.

Synthesis and Structure of a Cationic Platinum Borylene Complex

“…[17] The Pt À Br bond length (2.6246 (4) ) is comparable to that of trans-[(Cy 3 P) 2 Pt(Br){B(Fc)Br}] (2.6183 (8) ), but longer than that in trans-[(Cy 3 P) 2 PtBr 2 ] (2.435(1) ). [18] The PtÀB bond length (Pt1ÀB1 2.009 (4) ) is very similar to that in trans-[(Cy 3 P) 2 Pt(Br){B(Fc)Br}] (1.9963(34) ) [14] or trans-[(Ph 3 P) 2 Pt(Cl)(BCat)] (2.008 (8) ; Cat = catecholato). [19] The boryl group is oriented orthogonally to the {PtP 2 } fragment (C1-B1-Pt1-P1 90.6 (4)8 À ion can be detected at d = À7.55 ppm, probably owing to unresolved coupling to the platinum and phosphorus nuclei.…”

“…[8] While complexes with significant Pt À B multiple-bond character have so far remained unknown, the chemistry of platinum-boron compounds is otherwise very well-established. In particular, platinum boryl complexes of the type [L x Pt À BR 2 ] are numerous and thoroughly investigated, [9] mostly owing to their importance as key intermediates for the metal-mediated diboration of organic substrates.[10] Moreover, Pt and to a somewhat lesser extent Pd have proven to form transition-metal complexes with boron-centered ligands in far more unusual coordination modes, including metal base-stabilized boryl [11] and borylene species [3c, 12] or heterodinuclear borylene complexes.[13] Herein we report on the first platinum borylene species with a two-coordinate boron center and pronounced PtÀB-multiple-bond character.Recently, we described the formation of trans-[(Cy 3 P) 2 Pt(Br){B(Fc)Br}] (Fc = ferrocenyl) upon oxidative addition of [FcBBr 2 ] to [Pt(PCy 3 ) 2 ], [14] and its conversion to the unprecedented T-shaped three-coordinate platinum boryl complex trans-[(Cy 3 P) 2 Pt{B(Fc)Br}][BAr F 4 ] (3), which was obtained by selective bromide abstraction from the Pt center. Subsequently, 3 was converted to 1 by addition of 4-methylpyridine to the boron atom with concomitant formal migration of bromide from the B to Pt atom.…”

Aufbau einer B‐C‐Doppelbindung in der Koordinationssphäre des Platins: ein Alkylidenborylligand, der isoelektronisch zu neutralen Aminoborylenen ist

“…[11] Vor kurzem konnten wir eine Reihe von Platin-Iminoborylkomplexen trans-[(R 3 P) 2 BrPt(BNR 1 )] (E: R= Cy, R 1 = SiMe 3 ; F: R = Cy, R 1 = iBu; G: R = iPr, R 1 = SiMe 3 ) erhalten [12] und anschließend auch den ersten Oxoborylkomplex trans-[(Cy 3 P) 2 BrPt(B O)] (H). [13] [16] und verwandten Borylkomplexen gleichen. [15,17] …”

Experimental and DFT studies on poly[octa-μ3-acesulfamato-O,O:N,O′;O′,N:O,O-tetraaquatetrabarium(II)] complex

“…Based on facile oxidative addition of B-Br and B-I bonds to Pt(0) centres [6], we became interested in the reactivity of diboranes(4) Br 2 B 2 R 2 (R = NMe 2 , Mes) towards low-valent phosphine platinum complexes. We have now successfully accomplished the synthesis of two different types of diboranyl (4) 2 Pt(Br){B(Mes)B(Mes)Br}], which features a dative bond from the platinum to the second boron atom, resulting in a distorted square-pyramidal geometry of the platinum centre [7].…”