Novel basic ligands for the homogeneous catalytic carbonylation of methanol

Anion effects on the hydrolysis of the (.mu.-oxo)bis(pentaamminechromium(III)) ion in basic solution

“…The acid rhodo bromide salt [(NH3)5Cr(OH)Cr(NH3)5]Br5-2H20 was prepared through the aerobic oxidation of chromous bromide in concentrated aqueous ammonia, followed by acidification of the product mixture with HBr.10 A 1 M chromous bromide stock solution was prepared by the addition of Aldrich Gold Label chromium chunks to anaerobic (N2-purged) 2 M HBr. The crude acid rhodo product was recrystallized twice by dissolving in cold, 1 mM HBr and slowly adding cold, 1 M HBr. Anal.…”

“…Preparation of Complex 2. To a solution of trani-Cl2Ru(P'"0)2 (1) (330 mg, 0.5 mmol) and 1 equiv of Ph2PCH2CH2OCH3 in a hydrogensaturated mixture of 20 mL of methanol and 50 mL of benzene was added NaBH4 in small portions at 20 °C, until the initial red solution had turned to light yellow. The solvents were removed in vacuo at ambient temperature, leaving a yellow residue.…”

“…Although the electronic structures of the (p-oxo)bis(pentaamminechromium(III)) ion and related linear, oxo-bridged dimers have been probed extensively through spectroscopic and magnetic measurements,1-3 the reaction chemistry of rhodo and erythro chromium dimer species is not well understood. In particular, the thermodynamic and mechanistic basis for the most characteristic reaction of the basic rhodo dimer, hydrolysis to the hydroxo erythro ion (eq 1) in alkaline media, is not fully revealed in the [(NH3)5Cr]204+ + H20 -(NH3)5Cr(OH)Cr(NH3)4(OH)4+ + NH3 (1) several mechanistic studies of this process reported to date. [4][5][6] Having established the stoichiometry of reaction 1, Wilmarth and co-workers1 234 suggested that negative charge buildup on chromium owing to prr(0)-dir(Cr) bonding is responsible for the weakening of a Cr-N bond and ultimately displacement of NH3.…”