Half-SandwichB-Oxy Boratabenzene Ruthenium Complexes: Synthesis, Characterization, and Reactivity of (η⁶-C₅H₅BOR)RuCl(PPh₃)₂(R = Et, Me)

Abstract

The first examples of half-sandwich borata­benzene ruthenium complexes have been prepared and well-characterized. Treatment of RuCl2­(PPh3)3 with the anionic borata­benzene ligands C5H5­BORNa (R = Et, Me) produced the B-alkoxy complexes (η6-C5H5­BOR)­RuCl­((PPh3)2 (R = Et, 1a; Me, 1b), while the reaction of RuCl2­(PPh3)3 with the neutral bora­benzene–PPh3 adduct C5H5BPPh3 led to the formation of the dinuclear complex (μ2-η6,η6-C5H5­BOB­C5H5)­[RuCl­(PPh3)2]2 (2), with an oxo-bis­(borata­benzene) bridging ligand connected by the B–O–B linkage. The B-hydroxy complex (η6-C5H5­BOH)­RuCl­(PPh3)2 (3) was obtained from the nucleophilic substitution of complexes 1a, 1b, or 2 with water at the boron atoms, and the complexes 1a, 1b, 2, and 3 could interconvert through the nucleophilic substitution reactions. While the reaction of 1a with phenylacetylene did not successfully afford the vinylidene complex as expected, reactions of 1a with terminal ω-alkynols HCC­(CH2) n CH­(R)­OH (R = H, n = 1, 2; R = Me, n = 1) proceeded smoothly to provide the neutral oxacyclocarbene complexes (η6-C5H5­BOEt)­RuCl­(CCH2­CH2­CH2O)­(PPh3) (4), (η6-C5H5­BOEt)­RuCl­(CCH2­CH2­CH2­CH2O)­(PPh3) (5), and (η6-C5H5­BOEt)­RuCl­(CCH2­CH2­CH­(Me)­O)­(PPh3) (6) via intramolecular nucleophilic attack of the hydroxyl group to the corresponding vinylidene intermediates.

Efficient endo Cycloisomerization of Terminal Alkynols Catalyzed by a New Ruthenium Complex with 8‐(Diphenylphosphino)quinoline Ligand and Mechanistic Investigation

“…Consistent with the solid‐state structure, the 31 P{ 1 H} NMR spectrum (in CD 2 Cl 2 ) of 12 showed two doublet signals at δ =58.6 and 49.5 ppm ( J (PP)=31.3 Hz) for the two inequivalent phosphine groups. Owing to the chirality at the metal center, the two protons of each methylene group of the oxacyclocarbene ring (Ru=CC H 2 , Ru=COC H 2 , and Ru=COCH 2 C H 2 ) are diastereotopic, giving rise to a complicated 1 H NMR spectrum with three pairs of multiplet signals in the aliphatic region between δ =3.05 and 4.85 ppm, similar to that reported for other chiral ruthenium oxacyclocarbene complexes –. The 13 C{ 1 H} NMR spectrum displayed a Ru=C signal at δ =321.6 ppm ( 2 J (PC)=11.2 Hz), in agreement with those observed for other ruthenium oxacyclocarbene complexes .…”

Construction of Boron-Containing Aromatic Heterocycles

“…N-TBS-N′-allylethylenediamine 118 was synthesized by the treatment of N-allylethylenediamine (117) with nbutyllithium followed by reaction with TBSCl. Condensation of 118 with in situ generated allyldichloroborane (111) [1,5-a]pyridine is one of the isomers of 1,3,2-benzodiazaborole, and it can also be deemed an analogue of indolizine or isoindole. In 2001, the Weber group first reported its isolation (Scheme 39).…”

“…Half-sandwich boratabenzene ruthenium complexes were reported by the Wen group in 2015. 111 Treatment of boratabenzenes 219 with RuCl 2 (PPh 3 ) 3 produced the Balkoxy complexes 220 (Scheme 62). The reaction of 220 (R = Et) with terminal ω-alkynols 221 furnished rare examples of neutral monophosphine ruthenium oxacyclocarbene complexes 222, which was probably formed via the intermolecular nucleophilic attack at the neutral vinylidene intermediate facilitated by the more electrophilic ruthenium center.…”

“…The first example of a BN-fused indole was reported by the Liu group in 2010 70. Condensation reaction of N-t Bu-N′-allylethylenediamine 110 with in situ generated allyldichloroborane(111) afforded the cyclic compound 112 (Scheme 35). Subsequent ring-closing metathesis with Grubbs 1st generation catalyst A or Schrock's catalyst B gave the bicyclic molecule 113.…”