4-Coordinated, 14-electron ruthenium(ii) chalcogenolate complexes: synthesis, electronic structure and reactions with PhICl2 and organic azides.

The 4-coordinated RuII chalcogenolate complexes [Ru(STipp)2(PPh3)2] (Tipp = 2,4,6-triisopropylphenyl, 1) and [Ru(SeMes)2(PPh3)2] (Mes = 2,4,6-trimethylphenyl, 2) have been synthesized, and their reactions with PhICl2 and organic azides have been studied. Complex 2 synthesized from [RuII(PPh3)3Cl2] and NaSeMes displays a seesaw structure with P-Ru-P and Se-Ru-Se bond angles of 103.43(13) and 145.26(6)°, respectively. Natural bond order analyses revealed that in each of 1 and 2, there are two n →σ* (donor-acceptor) π interactions between the chalcogen lone pairs and the Ru-P antibonding molecular orbitals. The calculated second-order perturbation interaction energies of the two interactions for 1 (20.5 and 18.3 kcal mol-1) are stronger than those of 2 (13.6 and 11.0 kcal mol-1), suggesting the thiolate ligand (TippS-) is a stronger π-donor than the selenolate ligand (MesSe-) with respect to RuII. Chlorination of 1 with PhICl2 afforded the dichloride complex [Ru(STipp)2Cl2(PPh3)] (3), which was hydrolyzed to the hydroxo complex [Ru(STipp)2(OH)Cl(PPh3)] (4) after column chromatography on silica in air. Treatment of 4 with HCl and methyl triflate gave 3 and [Ru(STipp)2(OH)(OTf)(PPh3)] (OTf = triflate, 5), respectively. Reactions of 1 and 2 with p-tolyl azide (p-tolN3) afforded the tetrazene complexes [Ru{N4(p-tol)2}(ER)2(PPh3)] (ER = STipp (6), SeMes (7)), whereas that with tosyl azide (TsN3) gave the imido complexes [Ru(κ2-NTs)(STipp)2(PPh3)] (ER = STipp (8), SeMes (10)). The short Ru-Nimido distances in 8 [1.883(3) Å] and 10 [1.892(2) Å] are indicative of multiple bond character. Treatment of 8 with TsN3 afforded the tetrazene complex [Ru(N4Ts2)(STipp)2(PPh3)] (9), but no cycloaddition was found between 10 and TsN3. Nucleophilic attack of the imido ligand in 10 with methyl triflate yielded the amido complex [Ru(κ2-NMeTs)(SeMes)2(PPh3)](OTf) (11). The crystal structures of 2, 4, 6, and 8-11 have been determined.