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The kinetics of phosphine substitution in CpRu(PPh3)2X (X = Br, 1b, X = I, 1c, X = N3, 1d, and X = NCO, 1e) have been measured under pseudo-first order conditions in THF solution and compared with data for CpRu(PPh3)2X (1a). The relative rate of substitution is found to be 1a > 1d > 1b > 1e > 1c. Substitution rates decrease in the presence of added PPh3 and are independent of added X consistent with a dissociative process. Activation parameters for 1a–1c (ΔH† = 113–135 kJ mol−1, ΔS† = 21–102 J mol−1 K−1) and DFT calculations support a dissociative or dissociative interchange pathway even though negative activation entropies (ΔS† = −48 ± 16 to −105 ± 5 J mol−1 K−1) are observed for 1d–e. Differences in Ru–ligand bond angles in 1d–e point to different π-acceptor properties of the pseudohalide ligands, contributing to the faster rate of substitution for the azide complexes, 1d relative to the cyanate derivative 1e. Substitution is not observed when X = F, 1f, X = H, 1g, X = SnF3, 1h, or X = SnCl3, 1i. Compounds 1b–1e also react with chloroform to yield 1a. The rates of halide exchange are comparable to phosphine substitution for 1c and 1d. The latter reaction is inhibited by excess triphenylphosphine and is unaffected by both radical inhibitors and radical traps suggesting that a radical mechanism is unlikely.

The electrochemistry of ferrocene-substituted phosphines suggests electron loss from a largely ferrocene-based HOMO with significant phosphorus character rather than the exclusive oxidation of iron. In contrast, studies of the chemical oxidation of ferrocenylphosphines are limited. Reactions between FcPPh2 (1) and silver salts (AgCF3CO2, AgBF4, and AgOTf) lead to the silver-phosphine complexes [(FcPPh2)2Ag][CF3CO2] (11), [(FcPPh2)3Ag][BF4] (13), and [(FcPPh2)3Ag][OTf] (16), respectively, with no evidence for oxidation of FeII to FeIII. Compound 13 reacts with traces of water forming FcP(OBF3)Ph2 (15) which crystallizes in the P 1 ¯ space group with a = 10.326(4) A, b = 10.326(4) A, c = 17.445(6) A, α = 104.068(6)°, β = 99.970(7)°, and γ = 100.542(7)°. Reaction of 1 with excess AgOTf, however, yields a green, paramagnetic, FeIII complex: [(FcPPh2)Ag][OTf]2 (17) based on elemental analysis, ESR and Mossbauer spectroscopy. Reaction of 1 with bromine yields paramagnetic FcPPh2Br3 (10) by ESR spectroscopy. Reactions between ferrocenyl(phenyl)phosphines, FcnPPh3–n (1–3, Fc = C5H5FeC5H4, n = 1–3), and sulfur or selenium yield the corresponding ferrocenyl(phenyl)-phosphine chalcogenides, FcnP(E)Ph3–n (4–9, n = 1–3, E = S, Se). The crystal structures of (FcP(S)Ph2 (4) are reported; P21/c space group, a = 14.5187(16) A, b = 10.5915(12) A, c = 12.0004(13) A, α = 90°, β = 96.891(2)°, γ = 90°. Reaction of 4 with bromine is accompanied by the loss of sulfur also yields 10.

The kinetics of phosphine substitution in CpRu(PAr3)2Cl by PMePh2 under pseudo-first order conditions in CDCl3 have been measured for PAr3 = PPh3, 1a, PPh2(p-tol), 1b, P(p-tol)3, 1c, P(p-CH3OC6H4)3, 1d, and P(p-FC6H4)3), 1e. Activation parameters characteristic of a dissociative pathway (ΔH† = 110–124 ± 2 kJ mol−1, ΔS† = 16–44 ± 5–12 J mol−1 K−1) are observed for all five compounds. The rate of substitution in CpRu(PAr3)2Cl (1a) and CpRu[P(p-FC6H4)3]2Cl (1e) is independent of added chloride ion and decreases in the presence of excess PAr3, however, the rate of substitution in CpRu[P(p-CH3OC6H4)3]2Cl (1d) is first order in added chloride ion and is less dependent on added PAr3. A mechanism involving [CpRu(PAr3)2(PMePh2)]+[Cl]− intermediates contributes to the substitution in 1b–d.

We synthesized nanoscale TiO2-RuO2 alloys by atomic layer deposition (ALD) that possess a high work function and are highly conductive. As such, they function as good Schottky contacts to extract photogenerated holes from n-type silicon while simultaneously interfacing with water oxidation catalysts. The ratio of TiO2 to RuO2 can be precisely controlled by the number of ALD cycles for each precursor. Increasing the composition above 16% Ru sets the electronic conductivity and the metal work function. No significant Ohmic loss for hole transport is measured as film thickness increases from 3 to 45 nm for alloy compositions >= 16% Ru. Silicon photoanodes with a 2 nm SiO2 layer that are coated by these alloy Schottky contacts having compositions in the range of 13-46% Ru exhibit average photovoltages of 525 mV, with a maximum photovoltage of 570 mV achieved. Depositing TiO2-RuO2 alloys on nSi sets a high effective work function for the Schottky junction with the semiconductor substrate, thus generating a large photovoltage that is isolated from the properties of an overlying oxygen evolution catalyst or protection layer.

The kinetics of phosphine substitution in CpRu(PAr3)2Cl by PMePh2 under pseudo-first order conditions in CDCl3 have been measured for PAr3 = PPh3, 1a, PPh2(p-tol), 1b, P(p-tol)3, 1c, P(p-CH3OC6H4)3, 1d, and P(p-FC6H4)3), 1e. Activation parameters characteristic of a dissociative pathway (ΔH(†) = 110-124 ± 2 kJ mol(-1), ΔS(†) = 16-44 ± 5-12 J mol(-1) K(-1)) are observed for all five compounds. The rate of substitution in CpRu(PAr3)2Cl (1a) and CpRu[P(p-FC6H4)3]2Cl (1e) is independent of added chloride ion and decreases in the presence of excess PAr3, however, the rate of substitution in CpRu[P(p-CH3OC6H4)3]2Cl (1d) is first order in added chloride ion and is less dependent on added PAr3. A mechanism involving [CpRu(PAr3)2(PMePh2)](+)[Cl](-) intermediates contributes to the substitution in 1b-d.