Background: The plant phyllosphere is a well-studied habitat characterized by low nutrient availability and high community dynamics. In contrast, plant trichomes, known for their production of a large number of metabolites, are a yet unexplored habitat for microbes. We analyzed the phyllosphere as well as trichomes of two tomato genotypes (Solanum lycopersicum LA4024, S. habrochaites LA1777) by targeting bacterial 16S rRNA gene fragments. Results: Leaves, leaves without trichomes, and trichomes alone harbored similar abundances of bacteria (108–109 16S rRNA gene copy numbers per gram of sample). In contrast, bacterial diversity was found significantly increased in trichome samples (Shannon index: 4.4 vs. 2.5). Moreover, the community composition was significantly different when assessed with beta diversity analysis and corresponding statistical tests. At the bacterial class level, Alphaproteobacteria (23.6%) were significantly increased, whereas Bacilli (8.6%) were decreased in trichomes. The bacterial family Sphingomonadacea (8.4%) was identified as the most prominent, trichome-specific feature; Burkholderiaceae and Actinobacteriaceae showed similar patterns. Moreover, Sphingomonas was identified as a central element in the core microbiome of trichome samples, while distinct low-abundant bacterial families including Hymenobacteraceae and Alicyclobacillaceae were exclusively found in trichome samples. Niche preferences were statistically significant for both genotypes and genotype-specific enrichments were further observed. Conclusion: Our results provide first evidence of a highly specific trichome microbiome in tomato and show the importance of micro-niches for the structure of bacterial communities on leaves. These findings provide further clues for breeding, plant pathology and protection as well as so far unexplored natural pathogen defense strategies.

Reactions of the bis(benzylamine)platinum(II) complex [Pt(COMe)2(NH2Bn)2] (2; Bn = benzyl) with (2-py)3COR (2-py = 2-pyridyl), (2-py)2PhCOR, and (2-py)2(m-Tol)COR (m-Tol = 3-methylphenyl) afforded the neutral diacetylplatinum(II) complexes [Pt(COMe)2{(2-py)3COR}] (R = H (3a), Me (3b), Et (3c), Bn (3d)), [Pt(COMe)2{(2-py)2PhCOR}] (R = H (4a), Me (4b)), and [Pt(COMe)2{(2-py)2(m-Tol)COR}] (R = H (5a) Me (5b)), respectively, having, due to a κ2 coordination of the ligands, a 2-pyridyl (3), a phenyl (4), or a m-tolyl (5) ring as the pendant group. The identities of all complexes were unambiguously proved by high-resolution mass spectrometric investigations and by NMR (1H, 13C, 195Pt) and IR spectroscopy as well as by single-crystal X-ray diffraction analyses (3a–d). In methanol solution, complexes 3b–d and 5b show a dynamic behavior. The thermodynamic parameters of these dynamics have been determined by variable-temperature 1H NMR measurements (Eyring plots). Furthermore, extensive DFT calculations will be presented, which indicate that the dynamics are caused by the interplay of hindered and respectively unhindered rotations of the substituent R and/or the pendant group.

The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) reacted with 2-pyridyl-functionalized monoximes and with dioximes in the presence of NaOMe to yield oxime–diacetyl platinum(II) complexes [Pt(COMe)2(2-pyCR═NOH)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(HON═CR–CR═NOH)] (R/R = Me/Me, 5a; Ph/Ph, 5b; (CH2)4, 5c; NH2/NH2, 5d), respectively. The strong intramolecular O–H···O hydrogen bonds in these complexes give rise to an activation of the acetyl ligands for Schiff-base type reactions, thus forming with primary amines iminoacetyl platinum complexes [Pt(COMe)(CMe═NHR′)(2-pyCR═NO)] (R/R′ = H/Bn, 6a; Me/Bn, 6b; Ph/Bn, 6c; H/CH2CH2Ph, 6d; H/CH2CH═CH2, 6e; Bn = benzyl) and [{Pt(CMe═NHR′)2(ON═CR–CR═NO)}2] (R/R = Me/Me, 7a–d; Ph/Ph, 8a–d; (CH2)4, 9a; R′ = Bn, a; CH2CH2Ph, b; CH2CH═CH2, c; CH2CH2OH, d). The intramolecular N–H···O hydrogen bonds in type 6–9 complexes make clear that protonated iminoacetyl ligands (i.e., aminocarbene ligands) and deprotoanted oxime ligands are present. These complexes could also be obtained in reactions of [Pt(COMe)2(NH2R′)2] (3) with pyridyl-functionalized monoximes and with dioximes where type 4/5 complexes were found to be intermediates. In solution, the bis(iminoacetyl) complexes 7–9 were found to be present as dimers (as also 8a in the solid state) with smaller amounts of monomers. The importance of hydrogen bonds for activation of acetyl ligands was further evidenced by synthesis of complexes [Pt(COMe)2(2-pyCH═NOMe)] (10) and [Pt(COMe)2(HON═CMe–CMe═NOMe)] (11) bearing O-methylated oxime ligands and their reactivty toward amines. The hydrogen-bond activated acetyl and iminoacetyl ligands in type 5, 7, and 8 complexes were found to undergo in CD3OD solutions facile H/D exchange reactions resulting in complexes bearing C(CD3)═O/C(CD3)═NDR′ ligands. The constitution of all complexes was unambiguously confirmed analytically, spectroscopically and in part by single-crystal X-ray diffraction analyses. Structural and NMR parameters as well as DFT calculations gave evidence for relatively strong intramolecular hydrogen bonds.

The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) reacted with 2-pyridyl-functionalized monoximes and with dioximes in the presence of NaOMe to yield oxime–diacetyl platinum(II) complexes [Pt(COMe)2(2-pyCR═NOH)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(HON═CR–CR═NOH)] (R/R = Me/Me, 5a; Ph/Ph, 5b; (CH2)4, 5c; NH2/NH2, 5d), respectively. The strong intramolecular O–H···O hydrogen bonds in these complexes give rise to an activation of the acetyl ligands for Schiff-base type reactions, thus forming with primary amines iminoacetyl platinum complexes [Pt(COMe)(CMe═NHR′)(2-pyCR═NO)] (R/R′ = H/Bn, 6a; Me/Bn, 6b; Ph/Bn, 6c; H/CH2CH2Ph, 6d; H/CH2CH═CH2, 6e; Bn = benzyl) and [{Pt(CMe═NHR′)2(ON═CR–CR═NO)}2] (R/R = Me/Me, 7a–d; Ph/Ph, 8a–d; (CH2)4, 9a; R′ = Bn, a; CH2CH2Ph, b; CH2CH═CH2, c; CH2CH2OH, d). The intramolecular N–H···O hydrogen bonds in type 6–9 complexes make clear that protonated iminoacetyl ligands (i.e., aminocarbene ligands) and deprotoanted oxime ligands are present. These complexes could also be obtained in reactions of [Pt(COMe)2(NH2R′)2] (3) with pyridyl-functionalized monoximes and with dioximes where type 4/5 complexes were found to be intermediates. In solution, the bis(iminoacetyl) complexes 7–9 were found to be present as dimers (as also 8a in the solid state) with smaller amounts of monomers. The importance of hydrogen bonds for activation of acetyl ligands was further evidenced by synthesis of complexes [Pt(COMe)2(2-pyCH═NOMe)] (10) and [Pt(COMe)2(HON═CMe–CMe═NOMe)] (11) bearing O-methylated oxime ligands and their reactivty toward amines. The hydrogen-bond activated acetyl and iminoacetyl ligands in type 5, 7, and 8 complexes were found to undergo in CD3OD solutions facile H/D exchange reactions resulting in complexes bearing C(CD3)═O/C(CD3)═NDR′ ligands. The constitution of all complexes was unambiguously confirmed analytically, spectroscopically and in part by single-crystal X-ray diffraction analyses. Structural and NMR parameters as well as DFT calculations gave evidence for relatively strong intramolecular hydrogen bonds.

Reactions of the bis(benzylamine)platinum(II) complex [Pt(COMe)2(NH2Bn)2] (2; Bn = benzyl) with (2-py)3COR (2-py = 2-pyridyl), (2-py)2PhCOR, and (2-py)2(m-Tol)COR (m-Tol = 3-methylphenyl) afforded the neutral diacetylplatinum(II) complexes [Pt(COMe)2{(2-py)3COR}] (R = H (3a), Me (3b), Et (3c), Bn (3d)), [Pt(COMe)2{(2-py)2PhCOR}] (R = H (4a), Me (4b)), and [Pt(COMe)2{(2-py)2(m-Tol)COR}] (R = H (5a) Me (5b)), respectively, having, due to a κ2 coordination of the ligands, a 2-pyridyl (3), a phenyl (4), or a m-tolyl (5) ring as the pendant group. The identities of all complexes were unambiguously proved by high-resolution mass spectrometric investigations and by NMR (1H, 13C, 195Pt) and IR spectroscopy as well as by single-crystal X-ray diffraction analyses (3a–d). In methanol solution, complexes 3b–d and 5b show a dynamic behavior. The thermodynamic parameters of these dynamics have been determined by variable-temperature 1H NMR measurements (Eyring plots). Furthermore, extensive DFT calculations will be presented, which indicate that the dynamics are caused by the interplay of hindered and respectively unhindered rotations of the substituent R and/or the pendant group.

Reactions of the dinuclear platina-β-diketone [Pt2{(COR)2H}2(μ-Cl)2] (1) with K[(pz)3BH] and K[(3,5-Me2pz)3BH] (pz = pyrazolyl; 3,5-Me2pz = 3,5-dimethylpyrazolyl) afforded neutral diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3BH}] (4a) and [Pt(COMe)2H{(3,5-Me2pz)3BH}] (4b), bearing κ3-bonded tris(pyrazolyl)borate (scorpionate) ligands. These complexes were found to decompose in chloroform solution under formation of the respective chlorido complexes [Pt(COMe)2Cl{(pz)3BH}] (5a) and [Pt(COMe)2Cl{(3,5-Me2pz)3BH}] (5b) as the initial step. Diacetylplatinum(II) complexes with κ2-coordinated scorpionate ligands (K[Pt(COMe)2{(pz)3BH}], 6a; K[Pt(COMe)2{(3,5-Me2pz)3BH}], 6b; K[Pt(COMe)2{(pz)4B}], 7; K[{Pt(COMe)2}2{(pz)4B}], 8) were obtained in ligand exchange reactions of [Pt(COMe)2(NH2Bn)2] (3; Bn = benzyl) with the respective potassium (pyrazolyl)borates. The deprotonation of the hydrido complexes 4 with potassium methoxide led also to the formation of 6. Diacetylplatinum(II) complexes 6a and 7 were found to react in oxidative addition reactions with alkyl halides to yield diacetylplatinum(IV) complexes of the type [Pt(COMe)2R{(pz)3BH)}] (R = Me, 9a; Et, 9b; Bn, 9c) and [Pt(COMe)2R{(pz)4B}] (R = Me, 10a; Et, 10b; Bn, 10c), respectively, with κ3-bonded scorpionate ligands. The identities of all platinum complexes were unambiguously proved by microanalyses or by high-resolution mass spectrometric investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopies, and by single-crystal X-ray diffraction analyses (4a, 5a, 7·(18C6), 9c; 18C6 = 18-crown-6). The reactivity of the complexes is discussed in terms of hemilability of the scorpionate ligands.

Reactions of the dinuclear platina-β-diketone [Pt2{(COR)2H}2(μ-Cl)2] (1) with K[(pz)3BH] and K[(3,5-Me2pz)3BH] (pz = pyrazolyl; 3,5-Me2pz = 3,5-dimethylpyrazolyl) afforded neutral diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3BH}] (4a) and [Pt(COMe)2H{(3,5-Me2pz)3BH}] (4b), bearing κ3-bonded tris(pyrazolyl)borate (scorpionate) ligands. These complexes were found to decompose in chloroform solution under formation of the respective chlorido complexes [Pt(COMe)2Cl{(pz)3BH}] (5a) and [Pt(COMe)2Cl{(3,5-Me2pz)3BH}] (5b) as the initial step. Diacetylplatinum(II) complexes with κ2-coordinated scorpionate ligands (K[Pt(COMe)2{(pz)3BH}], 6a; K[Pt(COMe)2{(3,5-Me2pz)3BH}], 6b; K[Pt(COMe)2{(pz)4B}], 7; K[{Pt(COMe)2}2{(pz)4B}], 8) were obtained in ligand exchange reactions of [Pt(COMe)2(NH2Bn)2] (3; Bn = benzyl) with the respective potassium (pyrazolyl)borates. The deprotonation of the hydrido complexes 4 with potassium methoxide led also to the formation of 6. Diacetylplatinum(II) complexes 6a and 7 were found to react in oxidative addition reactions with alkyl halides to yield diacetylplatinum(IV) complexes of the type [Pt(COMe)2R{(pz)3BH)}] (R = Me, 9a; Et, 9b; Bn, 9c) and [Pt(COMe)2R{(pz)4B}] (R = Me, 10a; Et, 10b; Bn, 10c), respectively, with κ3-bonded scorpionate ligands. The identities of all platinum complexes were unambiguously proved by microanalyses or by high-resolution mass spectrometric investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopies, and by single-crystal X-ray diffraction analyses (4a, 5a, 7·(18C6), 9c; 18C6 = 18-crown-6). The reactivity of the complexes is discussed in terms of hemilability of the scorpionate ligands.

Reactions of the dinuclear platina-β-diketone [Pt2{(COR)2H}2(μ-Cl)2] (1) with K[(pz)3BH] and K[(3,5-Me2pz)3BH] (pz = pyrazolyl; 3,5-Me2pz = 3,5-dimethylpyrazolyl) afforded neutral diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2H{(pz)3BH}] (4a) and [Pt(COMe)2H{(3,5-Me2pz)3BH}] (4b), bearing κ3-bonded tris(pyrazolyl)borate (scorpionate) ligands. These complexes were found to decompose in chloroform solution under formation of the respective chlorido complexes [Pt(COMe)2Cl{(pz)3BH}] (5a) and [Pt(COMe)2Cl{(3,5-Me2pz)3BH}] (5b) as the initial step. Diacetylplatinum(II) complexes with κ2-coordinated scorpionate ligands (K[Pt(COMe)2{(pz)3BH}], 6a; K[Pt(COMe)2{(3,5-Me2pz)3BH}], 6b; K[Pt(COMe)2{(pz)4B}], 7; K[{Pt(COMe)2}2{(pz)4B}], 8) were obtained in ligand exchange reactions of [Pt(COMe)2(NH2Bn)2] (3; Bn = benzyl) with the respective potassium (pyrazolyl)borates. The deprotonation of the hydrido complexes 4 with potassium methoxide led also to the formation of 6. Diacetylplatinum(II) complexes 6a and 7 were found to react in oxidative addition reactions with alkyl halides to yield diacetylplatinum(IV) complexes of the type [Pt(COMe)2R{(pz)3BH)}] (R = Me, 9a; Et, 9b; Bn, 9c) and [Pt(COMe)2R{(pz)4B}] (R = Me, 10a; Et, 10b; Bn, 10c), respectively, with κ3-bonded scorpionate ligands. The identities of all platinum complexes were unambiguously proved by microanalyses or by high-resolution mass spectrometric investigations, by NMR (1H, 13C, 195Pt) and IR spectroscopies, and by single-crystal X-ray diffraction analyses (4a, 5a, 7·(18C6), 9c; 18C6 = 18-crown-6). The reactivity of the complexes is discussed in terms of hemilability of the scorpionate ligands.

Reactions of dinuclear μ-chlorido rhodium(I) complexes [(RhL2)2(μ-Cl)2] (L2 = cycloocta-1,5-diene, cod, 3; L2 = P∧P: Ph2PCH2PPh2, dppm, 4a; Ph2P(CH2)2PPh2, dppe, 4b; Ph2P(CH2)3PPh2, dppp, 4c; Me2P(CH2)2PMe2, dmpe, 4d) with γ-phosphino-functionalized propyl phenyl sulfides PhSCH2CH2CH2PR2 (R = Ph, 1; Cy, 2) afforded mononuclear rhodium(I) complexes of the type [RhCl(R2PCH2CH2CH2SPh-κP)L2] ] (R = Ph/L2 = P∧P, 5a−c; R = Ph/L2 = cod, 6; R = Cy/L2 = P∧P, 7a−d; R = Cy/L2 = cod, 8). Single-crystal X-ray diffraction analysis of 7b·C6H6 exhibited the expected square-planar coordination of the rhodium atom having coordinated dppe-κ2P,P′, Cy2PCH2CH2CH2SPh-κP, and a chlorido ligand. Deprotonation of complexes 5b/c, 6, 7b/c, and 8 with lithium diisopropyl amide (LDA) yielded, with a selective deprotonation of the CH2 group next to the sulfur atom (α-CH2 group), complexes of the type [Rh{CH(SPh)CH2CH2PR2-κC,κP}L2] (13b/c, 14, 15b/c, 16), thus being organorhodium intramolecular coordination compounds. Unexpectedly, reactions of the dppm complexes 5a and 7a with LDA led to deprotonation of the CH2 group of the dppm ligand, resulting in formation of mononuclear rhodium complexes with a bis(diphenylphosphino)methanide-κ2P,P′ ligand and a R2P∧SPh-κP,κS ligand, as well (17, 18). Single-crystal X-ray diffraction analysis of [Rh(dppm−H-κ2P,P′)(Cy2PCH2CH2CH2SPh-κP,κS)]·THF (18·THF) shows the rhodium atom located in the center of a distorted square-planar environment having bound the P∧S-κP,κS ligand and the anionic dppm−H-κ2P,P′ ligand with a very small P2−Rh−P3 angle (68.8(2)°) reflecting the small bite of that ligand. Addition of Tl[PF6] to complexes 5−8 afforded cationic rhodium(I) complexes of the type [Rh(R2PCH2CH2CH2SPh-κP,κS)L2][PF6] (9−12) bearing bidentately coordinated neutral co-ligands (P∧P: 9, 11; cod, 10, 12) and κP,κS-coordinated γ-phosphino-functionalized propyl phenyl sulfide ligands, as well. Single-crystal X-ray diffraction analysis of 10 reveals that the rhodium atom adopts a slightly distorted square-planar conformation. Complexes 9a−c and 11a−d were found to react with carbon monoxide, yielding cationic rhodium carbonyl complexes [Rh(CO)(R2PCH2CH2CH2SPh-κP,κS)(P∧P-κ2P,P′)]+ (19, 20), being in a dynamic equilibrium between two diastereomers each at room temperature, which was additionally verified by DFT calculations.

Reactions of dinuclear μ-chlorido rhodium(I) complexes [(RhL2)2(μ-Cl)2] (L2 = cycloocta-1,5-diene, cod, 3; L2 = P∧P: Ph2PCH2PPh2, dppm, 4a; Ph2P(CH2)2PPh2, dppe, 4b; Ph2P(CH2)3PPh2, dppp, 4c; Me2P(CH2)2PMe2, dmpe, 4d) with γ-phosphino-functionalized propyl phenyl sulfides PhSCH2CH2CH2PR2 (R = Ph, 1; Cy, 2) afforded mononuclear rhodium(I) complexes of the type [RhCl(R2PCH2CH2CH2SPh-κP)L2] ] (R = Ph/L2 = P∧P, 5a−c; R = Ph/L2 = cod, 6; R = Cy/L2 = P∧P, 7a−d; R = Cy/L2 = cod, 8). Single-crystal X-ray diffraction analysis of 7b·C6H6 exhibited the expected square-planar coordination of the rhodium atom having coordinated dppe-κ2P,P′, Cy2PCH2CH2CH2SPh-κP, and a chlorido ligand. Deprotonation of complexes 5b/c, 6, 7b/c, and 8 with lithium diisopropyl amide (LDA) yielded, with a selective deprotonation of the CH2 group next to the sulfur atom (α-CH2 group), complexes of the type [Rh{CH(SPh)CH2CH2PR2-κC,κP}L2] (13b/c, 14, 15b/c, 16), thus being organorhodium intramolecular coordination compounds. Unexpectedly, reactions of the dppm complexes 5a and 7a with LDA led to deprotonation of the CH2 group of the dppm ligand, resulting in formation of mononuclear rhodium complexes with a bis(diphenylphosphino)methanide-κ2P,P′ ligand and a R2P∧SPh-κP,κS ligand, as well (17, 18). Single-crystal X-ray diffraction analysis of [Rh(dppm−H-κ2P,P′)(Cy2PCH2CH2CH2SPh-κP,κS)]·THF (18·THF) shows the rhodium atom located in the center of a distorted square-planar environment having bound the P∧S-κP,κS ligand and the anionic dppm−H-κ2P,P′ ligand with a very small P2−Rh−P3 angle (68.8(2)°) reflecting the small bite of that ligand. Addition of Tl[PF6] to complexes 5−8 afforded cationic rhodium(I) complexes of the type [Rh(R2PCH2CH2CH2SPh-κP,κS)L2][PF6] (9−12) bearing bidentately coordinated neutral co-ligands (P∧P: 9, 11; cod, 10, 12) and κP,κS-coordinated γ-phosphino-functionalized propyl phenyl sulfide ligands, as well. Single-crystal X-ray diffraction analysis of 10 reveals that the rhodium atom adopts a slightly distorted square-planar conformation. Complexes 9a−c and 11a−d were found to react with carbon monoxide, yielding cationic rhodium carbonyl complexes [Rh(CO)(R2PCH2CH2CH2SPh-κP,κS)(P∧P-κ2P,P′)]+ (19, 20), being in a dynamic equilibrium between two diastereomers each at room temperature, which was additionally verified by DFT calculations.