In contrast to previous observations on phloem-limited geminiviruses supported in movement andaccumulation by RNA viruses such as cucumo- and tobamoviruses, tissue infiltration by Abutilon mosaic virus (AbMV) was enhanced by neither Tobacco mosaic virus nor Tomato mosaic virus (ToMV) in two different hosts, Nicotiana benthamiana and tomato. Both tobamoviruses exerted a negative effect on the DNA virus, resulting in a decrease in AbMV accumulation and significantly reduced infectivity in N. benthamiana. Despite these unexpected molecular observations, a striking synergistic enhancement in pathogenicity occurred with respectto stunting and necrosis. In situ hybridization revealed that this was not due to any alteration of tissue infiltration by AbMV, which also remained limited to the phloem in the mixed infections. Transgenically expressed ToMV 30K movement protein was not able to induce phloemescape of AbMV in tomato plants and did not lead to any obvious change in begomovirus symptomatology.

Different Nicotiana benthamiana lines stably transformed with Abutilon mosaic virus (AbMV) dimeric DNA B were capable of systemically spreading complete bipartite AbMV genomes, following agroinoculation of DNA A alone. Constitutively expressed viral movement protein (BC1) did not induce any persistent disease phenotype, but plants developed transient morphological abnormalities such as radially symmetric leaves after kanamycin withdrawal. Systemic AbMV infection produced symptoms and virus titers indistinguishable from those in non-transgenic plants. In systemically invaded leaves, the begomovirus remained phloem-limited, whereas the plants' susceptibility to mechanical transmission of AbMV was enhanced by a factor of three to five, as compared to non-transgenic controls. Hence, DNA B-encoded movement functions can complement local movement to the phloem after mechanical transmission, but fail to support viral invasion of non-phloem cells in systemically infected organs, indicating that the phloem restriction of AbMV does not result predominantly from a lack of transport competence in mesophyll tissues.

Co-2(CO)(8) reacts with bis(diphenylphosphanyl)amine, HN(PPh2)(2) (Hdppa, 1), in two steps to afford the known compound [Co(CO)(Hdppa-kappa(2)P)(2)][Co(CO)(4)]. 2THF (6a . 2THF). The intermediate [Co(CO)(2)(Hdppa-kappa(2)P).(Hdppa-kappa(2)P)][Co(CO)(4)]. dioxane . n-pentane (5 . dioxane . n-pentane) was isolated for the first time and was characterized by X-ray analysis. The cation 5(+) exhibits a slightly distorted trigonal-bipyramidal geometry. Detailed P-31-NMR investigations (solid-state CP/MAS NMR, TOSS, P-31-COSY, P-31-EXSY) showed that the additional tautomer [Co(CO)(2)(Hdppa-kappa(2)P) (Ph2P-N=P(H)Ph-2-kappa P)(+) (5'(+)) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state only tetragonal pyramidal species of 5 are found in solution. At -90 degrees C there is slow exchange between the three diastereomeric species 5a(+)-5c(+). Compound 5 forms [Co(CO).(Hdppa-kappa(2)P)(2)]BPh4. THF (6b . THF) in THF with NaBPh4 under GO-Elimination. A X-ray diffraction investigation shows that the cation 6(+) consists of a slightly distorted trigonal-bipyramidal co-ordination polyeder. However, a distorted tetragonal-pyramidal structure has been found for the cation 7(+) of the related compound [Co(CO)(dppm)(2)][Co(CO)(4)]. 2 THF (7 . 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph2PCH2PPh2). A comparison with the known [8] trigonal-bipyramidal stereoisomer, ascertained for 7(+) of the solvent-free 7, is described. In solutions of 6a . 2 THF and 7 . 2 THF C-13{H-1}- and P-31{H-1}-NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cation and cobalt(-I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism by forming binuclear substitution products such as the isolated Co-2(CO)(2).(mu-CO)(2)(mu-dppm)(2). 0.8 (3) over bar THF (8 . 0.8 (3) over bar THF), which was characterized by spectroscopy and X-ray analysis. For the dissolved [Co(CO)(2)CH3C(CH2PPh2)(3)][Co(CO)(4)]. 0.8 (3) over bar n-pentane (9a . 0.8 (3) over bar n-pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9a . 0.8 (3) over bar n-pentane with NaBPh4 yields [Co(CO)(2)CH3C(CH2PPh2)(3)]BPh4 (9b) which has been characterized by single-crystal X-ray analysis. The cation shows a small distorted tetragonal-pyramidal structure.

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Treatment of [Fe-2(CO)(9)] with bis(diphenylphosphino)amine, Ph(2)P-NH-PPh(2), dppa (1) in THF yields [(OC)(4)Fe(mu-dppa)Fe(CO)(4)] (5) and [Fe-2(CO)(6)(mu-CO)(mu-dppa)] . THF (6 . THF). Further reaction of 6 . THF with dppa gives [Fe-2(CO)(4)(mu-CO)(mu-dppa)(2)] . 2 THF (9 . 2 THF) by CO-substitution, whereas P(n-Bu)Ph(2), PPh(3) and PMe(3) add themselves to 6 . THF by forming the linear complexes [(OC)(4)Fe(mu-dppa)Fe(CO)(3)P(n-Bu)Ph(2)] (7a), [(OC)(4)Fe(mu-dppa)Fe(CO)(3)PPh(3)] (7b) and [(OC)(4)Fe(mu-dppa)Fe(CO)(3)PMe(3)] (7c). The reaction of 6 . THF with HPPh(2) or ClPPh(2) results in carbonyl loss and oxidative addition of the phosphorus-hydride, respectively the phosphorus-chloride, to the diiron centre yielding the iron(I) compounds [Fe-2(H)(mu-PPh(2))(CO)(5)(mu-dppa)] . THF (15 . THF) or [Fe-2(mu-Cl)(mu-PPh(2))(CO)(4)(mu-dppa)] . THF (16 . THF). Electrophilic attack of NOBF4 leads to cleavage of the diiron complex 6 . THF into [Fe(CO)(2)(NO)dppa]BF4 (17) and [Fe(CO)(5)] without oxidation of the iron centres. In the solid state, compound 17 forms linear as well as symmetrical bifurcated H-bonds to the BF4- anions. Furthermore, the NH group of 6 . THF can be deprotonated by n-BuLi. Treatment of 6 in its lithiated form with ClPPh(2) yields [Fe-2(mu-PPh(2))(mu-Ph(2)P-N-PPh(2))(CO)(6)] (10) by simultaneous CO loss. The structures of 5, 6 . THF, 7b, 9 . 2 THF, 10, 15 . CHCl3 and 17 were determined by X-ray crystallography. As the X-ray crystallographic studies show, the PNP backbone of the coordinated ligand 1 is conformatively highly flexible. All the compounds were also characterized by H-1 NMR, C-13{H-1} NMR, P-31{H-1} NMR, mass, and IR spectroscopy.

Co-2(mu-CO)(2)(CO)(4)(mu-Ph(2)P-NH-PPh(2)-P,P') . 1/2 C6H5CH3 (4 . 1/2 C6H5CH3) reacts with 2-butine-1,4-diol, HOCH2-C=C-CH2OH (5), to the dark-red tetrahedrane complex Co-2(CO)(4)(mu-eta(2)-eta(2)-HOCH2-C=C-CH2OH-C-2,C-3) . (mu-Ph(2)P-NH-PPh(2)-P,P') . THF (6 . THF). With t-butyl-phosphaacetylene, tBu-C=P (7), 4 . THF forms Co-2(CO)(4) . (mu-eta(2),eta(2))-tBu-C=P)(mu-Ph(2)P-NH-PPh(2)-P,P') (8), which also belongs to the tetrahydrane type. The compounds were characterized by their mass, IR, P-31{H-1} NMR, C-13{H-1} NMR, and H-1 NMR spectra. Crystals suitable for X-ray structure analyses have been obtained for 8 from dioxane. The dark red blocks crystallize in the monoclinic P2(1)/c space group with the lattice constants a = 1404,1(5), b = 1330,0(7), c = 2578,8(10) pm; beta = 90,82(3)degrees.

Reaction of Co2(CO)6(μ-η2,η2-HOCH2-CCCH2OH-C,C′) (5) with Ph2PNHPPh2 [bis(diphenylphosphino)amine, dppa, (2), P = C6H5] in toluene at 60°C gives [Co+1(CO)2{Ph2PNP(O)Ph⊖2 − P}(Ph2PNHPPh2)] (6), in which the ligand dppa was partially oxidized and deprotonated. Recrystallization of 6 from DMSO/methanol/n-hexane yields 6 · 2 CH3OH. The structure of 6 · 2CH3OH was determined by X-ray crystallography. The starting material 5 and 6 · 2 CH3OH were also characterized by 1H NMR, 13C{1H} NMR, 31P{1H} NMR and IR spectroscopy.

Reaction of Co-2(Co)(6)(mu-eta(2),eta(2)-HOCH2-C=C-CH2OH-C,C') (5) with Ph(2)P-NH-PPh(2)[bis(diphenylphosphino)amine, dppa, (2), Ph=C6H5] in toluene at 60 degrees C gives [Co+1(CO)(2){Ph(2)P - N - P(O)Ph(2)(c)ircle minus)-P)(Ph(2)P-NH-PPh(2))] (6), in which the ligand dppa was partially oxidized and deprotonated. Recrystallisation of 6 from DMSO/methanol/n-hexane yields 6 . 2 CH3OH. The structure of 6 . 2CH(3)OH was determined by X-ray crystallography. The starting material 5 and 6 . 2CH(3)OH were also characterized by H-1 NMR, C-13{1H} NMR, P-31{H-1} NMR and IR spectroscopy.

[Co2(mu-CO)2(CO)4(mu-dppa)] [5; dppa = (Ph2P)2NH] reacts with dppa (1) in toluene at 85-degrees-C within 15 minutes primary to give [Co2(CO)4(mu-dppa)2] (6). After about one hour a reductive P-N bond cleavage of the coordinated dppa in 6 takes place, accompanied by hydrogen transfer, yielding [(Co1+)2(mu-CO)(CO)4(dppa-)2] (7), the paramagnetic dinuclear complex [(Co1/2+)2(mu-PPh2-)(CO)2(mu-dppa)2] (8), and [(Co1+)2(mu-CO)(CO)3(mu-PPh2-)(mu-dppa-)PPh2NH2] (9). The three new compounds 7-9 have been characterized by X-ray analyses, H-1, C-13{H-1}-NMR, IR, ESR spectroscopy, and magnetic measurements.

The yield of the earlier published Co-2(mu-CO)(2)(CO)(4)(mu-dppa).1/2 C6H6(4.1/2 C6H6)[dppa = bis(diphenylphosphino)amin (1)] could now be increased from 30% to 80%. In the polar solvent tetrahydrofuran (THF) Co,(CO), and dppa react to the ionic complex [Co(CO)(dppa)(2)][Co(CO)(4)].2 THF(5a.2 THF). Metatheses of 5a.2 THF with NaBPh(4) in ethanol led to the formation of [Co(CO)(dppa)(2)]BPh(4) (5b). Under UV irradiation 4.1/2 C6H6 and dppa gives the CO-bridging-free Co-2(CO)(4)(mu-dppa)(2) (7a). The course of the reaction was studied by infrared spectroscopy. After adding n-hexane to the THF solution of 7a the CC-bridged isomer Co-2(mu-CO)(2)(CO)(2)(mu-dppa)(2) (7b) precipitates. The structure of 7b was determined by X-ray crystallography. Co-2(+1)(mu-CO)(CO)(4)(mu-PPh(2) - N - PPh(2)(theta))(mu-PPh(2)(theta)) (9) was prepared from 4.1/2 C6H6, n-butyllithium and CIPPh(2) in benzene. Suitable crystals for X-ray structural studies were obtained from a CH2Cl2/n-hexane mixture. The X-ray investigation showed that the Co-Co bond bridging anions[Ph(2)P - N - PPh(2)](theta) and PPh(2)(theta) are in trans position to each other in 9.CH2Cl2. With the cobalt atoms they form five and three membered rings in the same plane. All compounds were characterized by H-1 NMRI C-13{H-1}NMR, P-31{H-1} NMR and IR spectroscopy.