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Protonation of the co-ordinatively unsaturated species [Ru2(µsb-CO)2(CO)2(µ-etipdp)2][sb = semi-bridging, etipdp =(PriO)2PNEtP(OPri)2] by acids of non-co-ordinating conjugate bases, e.g. HBF4·OEt2, produced [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]+ which, as established X-ray crystallographically for the PF6– salt, contains both a bridging carbonyl and a bridging hydride ligand. This cationic species is very susceptible to attack by both neutral and anionic nucleophiles affording a range of product types. For instance, its reactions with anions X– which are capable of functioning as monodentate bridging ligands and which preferentially adopt the closed bridging co-ordination mode, e.g. halide and hydrogensulfide ions, afforded products of the type [Ru2(µ-X)H(µsb-CO)(CO)2(µ-etipdp)2](X = Cl, Br, I, SH, etc.), resulting from the substitution of a carbonyl group by the nucleophile. On the other hand, anionic nucleophiles such as H– and CN– gave addition products of the type [Ru2HX(CO)4(µ-etipdp)2](X = H, CN, etc.) in which the hydride and the X– ligand occupy equatorial sites trans disposed with respect to each other, as established in a separate study for [Ru2H2(CO)4(µ-etipdp)2]. Carbon monoxide also afforded a simple addition product, viz.[Ru2H(CO)5(µ-etipdp)2]+, but the majority of the other neutral nucleophiles studied, particularly the unsaturated systems, yielded products resulting from formal insertion of the nucleophile into the Ru–H bond. Thus sulfur produced [Ru2(µ-SH)(CO)4(µ-etipdp)2]+, while unsaturated nucleophiles of general formula X′Y′, e.g. PhCN and RCCH (R = H, Ph, etc.), gave products of the type [Ru2{µ-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2{µ-NC(H)Ph}(CO)4(µ-etipdp)2]+ or of the type [Ru2{µ-η2-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2(µ-η1 : η2-CHCHR)(CO)4(µ-etipdp)2]+. Heterocumulenes X″Y″Z″ such as CS2 and PhNCS behaved similarly affording products of general formula [Ru2{µ-η2-X″Y″(H)Z″}(CO)4(µ-etipdp)2]+ containing five-membered RuX″Y″Z″Ru rings. The co-ordinatively saturated pentacarbonyl [Ru2H(CO)5(µ-etipdp)2]PF6 gave products similar to those afforded by [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6 on reaction with systems of the type X′Y′ and X″Y″Z″ except that, for terminal alkynes such as PhCCH, alkenylcarbonyl-bridged products, e.g.[Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6, are produced. The crystal structures of the following compounds were determined : [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6, [Ru2(µ-I)H(µsb-CO)(CO)2(µ-etipdp)2], [Ru2{µ-N(CHPh)}(CO)4(µ-etipdp)2]PF6, [Ru2(µ-η1 : η2-CHCH2)(CO)4(µ-etipdp)2]PF6, [Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6 and [Ru2{µ-η2-SC(H)NPh}(CO)4(µ-etipdp)2]PF6.

Treatment of the formally unsaturated species [Ru2(µsb-CO)2(CO)2(µ-etipdp)2][sb = semi-bridging, etipdp =(PriO)2PNEtP(OPri)2] with silver(I) salts such as AgSbF6 or AgBF4 in MeCN or PhCN led directly to the formation of the disolvated species [Ru2(CO)4(RCN)2(µ-etipdp)2]X2(R = Me or Ph; X = SbF6 or BF4), with no intermediates being detected. In contrast, as established spectroscopically, oxidation of this complex with silver(I) salts in very weakly co-ordinating solvents such as acetone or methanol afforded silver adducts of the parent species. Also, reaction with the electron acceptor tcnq (7,7,8,8-tetracyano-p-quinodimethane) in tetrahydrofuran (thf) gave the electron-transfer salt [Ru2(η1-tcnq)(CO)4(thf)(µ-etipdp)2][tcnq], while with p-chloranil(tetrachloro-1,4-benzoquinone) produced [Ru2(µ-Cl)(CO)4(µ-etipdp)2][p-OC6Cl4O]2 as a consequence of the benzoquinone functioning as a chlorinating agent as well as an electron acceptor. Cyclic voltammograms of [Ru2(µsb-CO)2(CO)2(µ-etipdp)2] and [Ru2(CO)4(RCN)2(µ-etipdp)2][SbF6]2(R = Me or Ph) have been measured in both aceto- and benzo-nitrile and are readily interpreted in terms of the redox process [Ru2(µsb-CO)2(CO)2(µ-etipdp)2]+ 2RCN [graphic omitted] [Ru2(CO)4(RCN)2(µ-etipdp)2]2+. The structure of the acetonitrile species [Ru2(CO)4(MeCN)2(µ-etipdp)2][BF4]2·CH2Cl2 has been determined X-ray crystallographically.

Thermolysis of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2], [Ru2H2(CO)4{µ-(RO)2PN(Et)P(OR)2}2] or [Ru2{µ-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) under appropriate reaction conditions affords the formally unsaturated species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2], which have been established by X-ray crystallography for both R = Me and R = Pri to contain two complementary semi-bridging carbonyl groups as well as two terminal carbonyls. These compounds are highly labile and react under mild conditions with a range of small molecule nucleophiles and electrophiles including carbon monoxide, isonitriles, nitrosyl ions, alkynes, sulfur, hydrogen sulfide, dioxygen, sulfur dioxide, tin(II) chloride, dihydrogen, protons, halogens and carbon tetrachloride. The compound [Ru2H2(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2], the product of the reaction involving dihydrogen and the tetraisopropoxy-diphosphazane derivative and in which, as determined by X-ray crystallography, the hydrogens are situated equatorially and trans to each other on different ruthenium atoms, is also highly reactive, typically reductively eliminating dihydrogen in its reactions with nucleophiles including alkynes.

The growth and growth dynamics of juvenile Atlantic salmon (Salmo salar) exposed from mid-August to mid-December to either a normal light:dark cycle (LDN) or a constant 16-h light:8-h dark (LD 16:8) photoperiod were compared. Exposure to the LD 16:8 resulted in 38.1% of the fish entering the upper modal group (UMG) of the length–frequency distribution, while only 15.4% entered the UMG under LDN. The length at which fish entered the UMG (critical fork length) did not differ between photoperiods. Fish in the small (5.8–6.7 cm) and middle (6.8–7.7 cm) size-ranges under LD 16:8 had greater growth rates than fish in the same size-ranges under LDN. Fish in the large (8.3–9.2 cm) size-range showed no significant variation in growth rates between photoperiods. At the end of the experiment, mean thyroxine (T4) levels were significantly (P 3) levels and the T3/T4 ratio were elevated under LD 16:8.

Treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with o-chloranil leads to electron transfer and the fission of one of the diphosphazane ligands to form [Ru2{µ-(RO)2PN(Et)C(O)}{(RO)2POC6Cl4O}(CO)4{µ-(RO)2PN(Et)P(OR)2}], characterized by X-ray crystallography for R = Me, and found to contain a chelating (MeO)2POC6Cl4O group and a novel bridging ligand derived by the coupling of a (RO)2PN(Et) fragment to a co-ordinated carbonyl group; in contrast, reaction with p-chloranil gives the radical anion salt [Ru2Cl(CO)5{µ-(RO)2PN(Et)P(OR)2}2][p-OC6Cl4O] resulting from the p-chloranil functioning as a chlorinating agent as well as an electron acceptor.