Visible-Light Photoisomerization and Photoaquation oftrans-[Ru(1,3,5-triaza-7-phosphaadamantane)₄Cl₂] in Organic Solvent and Water

Abstract

The interaction of the PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) ruthenium complex trans-[RuCl(2)(PTA)(4)] (trans-1) with visible light in chloroform and in water has been studied at room temperature. The complex trans-1 isomerizes to the cis isomer in CHCl(3) with radiation of lambda > 416 nm (Phi(434 nm) (CHCl(3)) = 0.13 +/- 0.01). The isomerization reaction is reversible as cis-1 is transformed into trans-1 with lambda = 367 nm (Phi(367 nm) (CHCl(3)) = 0.25 +/- 0.02). Irradiation at lambda > 416 nm of a solution of trans-1 in water leads to the cis-isomer complex and to the aqua complex (OC-6-32)-[RuCl(H(2)O)(PTA)(4)]Cl (2Cl) by a photoisomerization and photoaquation reaction (Phi(434 nm) (D(2)O) = 0.27 +/- 0.02). The mole ratio of cis-1 to 2Cl is not dependent on the pH but on the concentration of the products in solution. Isomerization in water is not reversible even if only cis-1 is present in solution. Synthesis and characterization of (OC-6-32)-[RuCl(H(2)O)(PTA)(4)](CF(3)SO(3)) (2CF(3)SO(3)) are also presented.

Neutral 1,3,5‐Triaza‐7‐phosphaadamantane‐Ruthenium(II) Complexes as Precursors for the Preparation of Highly Water‐Soluble Derivatives

“…We also reinvestigated the behavior of the two isomers in aqueous solution. In agreement with published data, 2 equilibrates rapidly with the monoaqua species cis ‐[RuCl(OH 2 )(PTA) 4 ] + ( 2 aq ), which was isolated as a PF 6 – salt by following another synthetic route (see below). The 31 P NMR resonances of the mixture of 2 and 2 aq were readily distinguished in a P–P COSY spectrum (Figure S7).…”

“…On the basis of the spectrum of 1 (Table ) and literature data, the most shielded triplet was assigned to the pair of mutually trans PTA ligands. The previously unreported 1 H NMR spectrum of 2 in CDCl 3 (contrary to previous reports, 2 is considerably less soluble than 1 in this solvent) is more complex and consists of two relatively broad singlets (12 H each) at δ = 4.04 and 4.47 ppm and a multiplet (24 H) centered at δ = 4.48 ppm (Supporting Information, Figure S4). The singlets (or better, unresolved multiplets) belong to the NC H 2 P groups of the two pairs of equivalent PTA ligands: in the H–H COSY spectrum, they are both coupled to the multiplet (generated by the NC H 2 N groups), whereas in the heteronuclear single quantum coherence (HSQC) spectrum (Figure S5) they have distinct cross‐peaks with carbon atoms that resonate in the N C H 2 P region (Table ).…”

“…In short, 1 is the kinetic product of the synthetic procedure from hydrated RuCl 3 and it isomerizes to the thermodynamically stable cis isomer 2 in aqueous solution. Later, Romerosa and co‐workers established that light can play an important role in the interconversion of the two isomers …”

“…In our hands, the best synthetic procedure for the preparation of 2 was the irradiation of an aqueous solution of 1 with blue light ( λ = 470 nm) for 1 h . The evaporation of the solvent afforded pure 2 quantitatively (according to NMR spectroscopy analysis).…”

The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble Ru(II)–phosphane complexes and in the catalysis of redox isomerization of allylic alcohols in aqueous–organic biphasic systems

“…The same signal was observed when 1 was dehalogenated in reaction with AgNO3, followed by addition of 4 equivalents of pta. [34] It is also worth mentioning, that in contrast to the reaction of [Ru(H2O)6] 2+ and pta, formation of mono-or tris-phosphane complexes was not observed.…”