Rhenium(I) Tricarbonyl Complexes with Poly(azolyl)borates Generated in Situ from an Organometallic Precursor Containing the B−H···Re Coordination Motif

Abstract

Complex fac-[Re(kappa(3)-H(mu-H)(2)B(tim(Me)))(CO)(3)] (1) reacts with protic azoles, like 2-mercapto-1-methylimidazole (tim(Me)H), 2-mercaptobenzothiazole (bztH), or pyrazoles (pz*H), to afford fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(2)(CO)(3)] (2), fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(bzt))(CO)(3)] (3), fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(pz))(CO)(3)] (4), fac-[Re(kappa(3)-HB(tim(Me))(pz)(2))(CO)(3)] (5), and fac-[Re(kappa(3)-H(mu-H)B(tim(Me))(3,5-Me(2)-4-EtOOCCH(2)pz))(CO)(3)] (6). Complexes 2-6 are stabilized by tridentate poly(azolyl)borates generated in situ, and their formation involves most probably a metal-assisted process which is considerably faster for the pyrazole derivatives. The characterization of the novel complexes, 3-6, has been done by common analytical techniques, including single crystal X-ray diffraction analysis. The solid state structures confirmed the presence of hybrid heteroscopionates, presenting (kappa(3)-H, S, S'), (kappa(3)-H, S, N), or (kappa(3)-S, N, N) binding motifs. Multinuclear ((1)H, (13)C, and (11)B) NMR studies have also shown that the coordination mode found in the solid state is retained in solution.

Design, Synthesis, and Chemistry of Bis(σ)borate and Agostic Complexes of Group 7 Metals

“…Overall, the coordination around the central metal atom in 5 and 6 can be described as a slightly distorted octahedron with an M‐H‐B angle of 127.57° ( 5 ) or 133.39° ( 6 ). Although the Re⋅⋅⋅H−B bond length in 5 (Re1−H17A=1.79(7) Å) is significantly shorter than in [Re(CO) 3 (μ‐H)HB( tim Me)(bt))] (1.90(4) Å) and [Re(CO) 3 (μ‐H)HB( tim Me)(pz)] ( tim Me=2‐mercapto‐1‐methylimidazolyl), bt=2‐mercaptobenzothiazolyl, and pz=pyrazolyl) (1.95(3) Å), the Re−S bond lengths in 5 (2.4475(17) and 2.4938(14) Å) are within the same range. Interestingly, the Mn−H bond length in 6 (1.65(3) Å) is comparable to that in 1 , 3 , and other related complexes, but shorter than in 4 .…”

“…Group 7m etal complexes that contain fac-M(CO) 3 moieties with [M]···HÀBa gostic interactions are of interest due to their bioactivity in radiopharmaceuticals. [24] The Na[(H 3 B)bbza] (bbza = bis(benzothiazol-2-yl)amine) ligand can react with ar ange of metals because it possessesb oth ah ard( nitrogen) and soft (sulfur) 1; Scheme1). [25] Complex 1 wasi solated by thin layer chromatographic (TLC) separation andc haracterizedb yI Ra nd NMR spectroscopy,m ass spectrometry,a nd single-crystal X-ray diffraction analysis.…”

“…[21, 22, 23a] This prompted us to assess the reactivityo fN a[(H 3 B)abz] [28] (abz = 2-aminobenzothiazolyl) in the presence of [Mn 2 (CO) 10 ]. Notably,t he composition of Na[(H 3 B)abz]a nd Na[(H 3 B)mbz] [24] differ only in terms of the exocyclic group present in the ligands (NH 2 or SH, respectively).A ss hown in Scheme 1, photolysis of either two or four equivalents of Na[(H 3 B)abz] with [Mn 2 (CO) 10 ]g ave the bis(s)bo- (17), Mn1ÀN20 2.0616(11), B11ÀH11B 1.226 (17), B11ÀH11C 1.241(18), B11ÀN12 1.502(2), N12ÀC19 1.3523 (17), N20ÀC19 1.3379 (17), N20ÀC211.3873 (17),N 22ÀC21 1.2967 (17), S1ÀC19 1.7454(14),S 2 ÀC21 1.7591(14);N12-B11-Mn1 108.49(10), C19-N20-C21 117.24 (11). rate [Mn(CO) 3 (m-H) 2 BH-(HN 2 CSC 6 H 4 )] (3)a nd the agostic complex [Mn(CO) 3 (m-H)BH(HN 2 CSC 6 H 4 ) 2 ]( 4), respectively. [25] The mass spectra of 3 and 4 show molecular ion peaks at m/z 302.9828 and 450.9908, respectively.T he 11 B{ 1 H} NMR spectrum of 3 features ad ownfield signal at d = 13.4 ppm, whereas 4 shows an upfield signal at d = À9.2 ppm.…”

Tricarbonylrhenium(I) Complexes with N‐Heterocyclic Thiones and Selenols

“…[19] Following in part the latter approach, we attempted reactions between [Re(CO) 5 Br] and HSpy or (Sepy) 2 in boiling THF with prolonged reaction times (Scheme 4). The more drastic conditions in the literature [19] and the use of [Re 2 (CO) 10 ] as starting material appeared to be inappropriate with regard to the widely unclear course of this reaction. When [Re(CO) 5 Br] was heated under reflux with 3 equiv.…”

“…[6][7][8] Recently, they have also been considered for potential radiopharmaceutical applications as tricarbonyl rhenium and technetium compounds. They have been included as coordination sites of pincer-type chelators [9,10] or used as components for so-called [2+1] complexes. [11] The structural chemistry of rhenium(I) tricarbonyl complexes with simple N-heterocyclic thiols mainly focuses to mercaptopyridine, mercaptoimidazol, mercaptopyrimidine or related ligands.…”