Synthesis of Ruthenium Boryl Analogues of the Shvo Metal−Ligand Bifunctional Catalyst

Abstract

Metal boryl complexes have received significant attention in the literature in recent years due to their role as key intermediates in a number of metal-catalyzed borylation reactions. The ligand scaffold is known to have a significant impact on the observed reactivity of these metal boryl complexes. A synthetic strategy to access ruthenium boryl analogues of the Shvo metal-ligand catalysts is described. Heating a precursor to Shvo's catalyst (1) with bis(catecholato)diboron at 50 °C provided ruthenium boryl complex 3 [2,5-Ph 2 -3,4-Tol 2 (η 5 -C 4 COBcat)Ru(CO) 2 Bcat] (Bcat = catecholatoboryl). Addition of bis(catecholato)diboron to complex 1 in the presence of a phenol results in ruthenium boryl complex5 [2,5-Ph 2 -3,4-Tol 2 (η 5 -C 4 COH)Ru(CO) 2 Bcat] at 22 °C in 30% isolated yield. A single crystal X-ray analysis of complex 5 confirmed the assigned structure. An improved synthesis of ruthenium boryl complex 5 was developed by the in situ formation of complex 3 [2,5-Ph 2 -3,4-Tol 2 (η 5 -C 4 COBcat)Ru(CO) 2 Bcat] followed by addition of the phenol, resulting in a 51% yield.

Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

“…The silica support, in the form of SBA-15 type MSN characterized by a hexagonal array (p6mm) of 9.7 nm diameter pores and a surface area of 385 m 2 /g, was produced by hydrolysis−condensation of tetramethylorthosilicate using the Pluronic P104 template, calcined at 550°C, washed with water, then heated at 550°C under vacuum, and subsequently stored in a glovebox away from ambient air and moisture. 44 The SiOH group surface concentration of 1.7 mmol/g was determined by measuring the concentration of toluene produced in a titration with Mg(CH 2 Ph) 2 (O 2 C 4 H 8 ) 2 53 and by spin counting of Q 3 -sites with 29 Si DPMAS NMR spectroscopy (1.6 mmol/g). Thusprepared MSN and Zr(NMe 2 ) 4 react in benzene at room temperature for 20 h producing Zr(NMe 2 ) n @MSN, a grafted material that we will contend is primarily monopodal tris(dimethylamido)zirconium, with smaller amounts of bipodal species bis(dimethylamido)zirconium and bis(dimethylamido) (dimethylamino)zirconium (eq 1).…”

“…26 Hydroboration of aldehydes and ketones is catalyzed by soluble titanium, 27 molybdenum, 28 as well as a few late metal catalysts. 29,30 Recently, divalent germanium and tin compounds were also shown to catalyze this reaction, and hydrides were postulated intermediates. 31 Group 4-catalyzed carbonyl hydrosilylations and hydrogenations are also known, 11,32−35 and although Schwartz's reagent catalyzes hydroboration of alkynes, 36 we are not aware of previous reports of zirconium-catalyzed hydroboration of carbonyls.…”

Preparation and characterisation of a Ni2+/Co2+-cyclam modified mesoporous cellular foam for the specific immobilisation of His6-alanine racemase

“…There are many types of ruthenium catalysts depending on the ligand attached to the metal; the most active one is the Shvo-type catalyst 133 . However, some disadvantages have been reported for the ruthenium catalyst, such as difficulty in its separation and reuse.…”

Alcohol Dehydrogenation with a Dual Site Ruthenium, Boron Catalyst Occurs at Ruthenium

“…By replacing the proton in the transition state with a Lewis acid, we propose to enable abstraction of hydrides from groups other than alcohols [28]. Our first plan to prepare a dual site ruthenium, boron hydride transfer catalyst was to functionalize Shvo's catalyst with a boronic ester as sketched in 4 (Scheme 1) [32]. Along these lines, Tim Clark has realized such a transition state with the Shvo scaffold in reduction chemistry, and has reported that 5 will catalyze aldehyde and aldimine hydroboration with a transition state such as 4 [33].…”