Synthesis of a Zwitterionic P-Coordinated Complex with Bis(diphenylphosphino)acetylene

Bis(acetylacetonato)ruthenium(ii) complexes containing alkynyldiphenylphosphines. Formation and redox behaviour of [Ru(acac)2(Ph2PCCR)2] (R = H, Me, Ph) complexes and the binuclear complex cis-[{Ru(acac)2}2(µ-Ph2PCCPPh2)}2]

Two equivalents of Ph(2)PC triple bond CR (R=H, Me, Ph) react with thf solutions of cis-[Ru(acac)(2)(eta(2)-alkene)(2)] (acac=acetylacetonato; alkene=C(2)H(4), 1; C(8)H(14), 2) at room temperature to yield the orange, air-stable compounds trans-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=H, trans-3; Me=trans-4; Ph, trans-5) in isolated yields of 60-98%. In refluxing chlorobenzene, trans-4 and trans-5 are converted into the yellow, air-stable compounds cis-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=Me, cis-4; Ph, cis-5), isolated in yields of ca. 65%. From the reaction of two equivalents of Ph(2)PC triple bond CPPh(2) with a thf solution of 2 an almost insoluble orange solid is formed, which is believed to be trans-[Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))](n) (trans-6). In refluxing chlorobenzene, the latter forms the air-stable, yellow, binuclear compound cis-[{Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))}(2)] (cis-6). Electrochemical studies indicate that cis-4 and cis-5 are harder to oxidise by ca. 300 mV than the corresponding trans-isomers and harder to oxidise by 80-120 mV than cis-[Ru(acac)(2)L(2)] (L=PPh(3), PPh(2)Me). Electrochemical studies of cis-6 show two reversible Ru(II/III) oxidation processes separated by 300 mV, the estimated comproportionation constant (K(c)) for the equilibrium cis-6(2+) + cis6 <=> 2(cis-6(+)) being ca. 10(5). However, UV-Vis spectra of cis-6(+) and cis-6(2+), generated electrochemically at -50 degrees C, indicate that cis-6(+) is a Robin-Day Class II mixed-valence system. Addition of one equivalent of AgPF(6) to trans-3 and trans-4 forms the green air-stable complexes trans-3 x PF(6) and trans-4 x PF(6), respectively, almost quantitatively. The structures of trans-4, cis-4, trans-4 x PF(6) and cis-6 have been confirmed by X-ray crystallography.

Syntheses, Structures, and Redox Properties of Dimeric Triruthenium Clusters Bridged by Bis(diphenylphosphino)acetylene and -ethylene

Reactions of oxo-centered triruthenium acetate complexes [Ru3O(OAc)6(py)2(CH3OH)](PF6) (py = pyridine, OAc = CH3COO-) (1) with nearly equimolar amounts of dppa [bis(diphenylphosphino)acetylene] or dppen [trans-1,2-bis(diphenylphosphino)ethylene] gave [Ru3O(OAc)6(py)2(L)](PF6) (L = dppa, 2; dppen, 3). With 2.4 equiv of 1, the reactions provided diphosphine-linked triruthenium dimers, [[Ru3O(OAc)6(py)2]2(L)](PF6)2 (L = dppa, 4; L = dppen, 5), respectively. Similarly, the reactions of [Ru3O(OAc)6(L')2(MeOH)]+ [L' = dmap (4-(dimethylamino)pyridine), 1a; L' = abco (1-azabicyclo[2.2.2]octane), 1b] with dppen gave dppen-linked dimers, [[Ru3O(OAc)6(dmap)2]2(dppen)](SbF6)2 (6) and [[Ru3O(OAc)6(abco)2]2(dppen)](BF4)2 (7), respectively. The chemical reduction of 2, 4, and 5 by hydrazine afforded one- or two-electron-reduced, neutral products, Ru3O(OAc)6(py)2(dppa) (2a), [Ru3O(OAc)6(py)2]2(dppa) (4a), and [Ru3O(OAc)6(py)2]2(dppen) (5a), respectively. The complexes were characterized by elemental analyses, ES-MS, UV-vis, IR, and 31P NMR spectroscopies, and cyclic and differential-pulse voltammetries. The molecular structures of compounds 2, 4, 5, 5a, 6, and 7 were determined by single-crystal X-ray diffraction. In 0.1 M (Bu4N)PF6-acetone, the monomers and dimers of triruthenium clusters show reversible and multistep redox responses. The two triruthenium cluster centers in dimers undergo stepwise reductions and oxidations due to the identical redox processes of the individual Ru3O cluster cores, suggesting the presence of electronic communications between them through the conjugated diphosphine spacer. The redox wave splitting mediated by dppa containing an ethynyl group (C triple bond C) is found to be more extensive than that by dppen containing an ethenyl (C=C) one. It appears that the redox wave splitting is enhanced by the introduction of electron-donating substituents on the auxiliary pyridine rings.

The synthesis and structural characterization of linear and macrocyclic bis(dinitrosyliron) complexes supported by bis(phosphine) bridging ligands

Reactions involving Fe(NO)2(CO)2 and the bis(phosphine) ligands bis(diphenylphosphino)methane (DPPM), bis(diphenylphosphino)acetylene (DPPA), 1,6-bis(diphenylphosphino)hexane (DPPH), and 1,4-bis(diphenyl phosphino)benzene (DPPB) have been examined. From these reactions, the mononuclear complex, Fe(κ1-DPPM)(NO)2(CO) 3, linear dinuclear species of the type Fe2(µ-L)(NO)4(CO)2 (L = Ph2PCH2PPh2 4, Ph2PC[Formula: see text]CPPh2 5, Ph2PCH2(CH3)4CH2PPh2 6, and Ph2P(p-C6H4)PPh2 7), and macrocyclic dinuclear species of the type Fe2(µ-L)2(NO)4 (L = Ph2PCH2PPh2 8 and Ph2PC[Formula: see text]CPPh2 9) were isolated and spectroscopically characterized. For 4, 5, 8, and 9, the solid-state molecular structures of the products were determined by use of single-crystal X-ray diffraction techniques. Key words: dinitrosyliron, iron nitrosyls, dinuclear macrocycles, bis(phosphine) complexes.