Dilution principle in two dimensions: One building block yields three forms of aggregation on variation of the surface concentration of the molecular precursor (see picture; ML=monolayer coverage). Upon annealing at 300 °C, highly robust 2D aggregates are obtained on metal surfaces which lend themselves to the construction of hierarchic systems of higher complexity.

A comprehensive investigation into the cooperative reactivity of two chemically complementary metal-complex fragments in early-late heterodinuclear complexes has been carried out. Reaction of the partially fluorinated tripodal amidozirconium complexes [HC-(SiMe2NR)3Zr(mu-Cl)2Li(OEt2)2] (R = 2-FC6H4: 2a, 2,3,4-F3C6H4: 2b) with K[CpM(CO)2] (M=Fe, Ru) afforded the stable metal-metal bonded heterodinuclear complexes [HC[SiMe2NR]3-Zr-MCp(CO)2] (3-6). Reaction of the dinuclear complexes with methyl isonitrile as well as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Two of these complexes, [HC[SiMe2N(2-FC6-H4)]3Zr(S2C)Fe(CO)2Cp] (9a) and [HC-[SiMe2N(2-FC2H4)]3Zr-(SCNPh)Fe(CO)2-Cp] (12), have been structurally characterized by a single crystal X-ray structure analysis, proving the structural situation of the inserted substrate as a bridging ligand between the early and late transition metal centre. The reactivity towards organic carbonyl derivatives proved to be varied. Reaction of the heterobimetallic complexes with benzyl and ethylbenzoate led to the cleavage of the ester generating the respective alkoxozirconium complexes [HC[SiMe2N(2-FC6H4)]3ZrOR] (R = Ph-CH2: 13a, Et: 13b) along with [CpFe-[C(O)Ph](CO)2], whereas the analogous reaction with ethyl formate gave 13b along with [CpFeH(CO)2]; this latter complex results from the instability of the formyliron species initially formed. Aryl aldehydes were found to react with the Zr-M complexes according to a Cannizzaro disproportionation pattern yielding the aroyliron and ruthenium complexes along with the respective benzoxyzirconium species. The transfer of the aldehyde hydrogen atom in the course of the reaction was established in a deuteriation experiment. [HC[SiMe2-N(2-FC6H4)]3Zr-M(CO)2Cp] reacted with lactones to give the ring-opened species containing an alkoxozirconium and an acyliron or acylruthenium fragment; the latter binds to the early transition metal centre through the acyl oxygen atom, as evidenced from the unusuallly low-field shifted 13C NMR resonances of the RC(O)M units. Ketones containing a-CH units react with the Zr-Fe complexes cooperatively to yield the aldol coupling products coordinated to the zirconium complex fragment along with the hydridoiron compound [CpFeH(CO)2], whereas 1,2-diphenylcyclopropenone underwent an oxygen transfer from the keto group to a CO ligand to give a linking CO2 unit and a cyclopropenylidene ligand coordinated to the iron fragment in [HC-[Si(CH3)2N(2,3,4-F3C6H2)]3Zr(mu-O2C)-Fe(CO)[C3Ph2)Cp] (19). The atom transfer was established by 17O and 13C labelling studies. Similar oxygen-transfer processes were observed in the reactions with pyridine N-oxide, dimethylsulfoxide and methylphenylsulfoxide.

Reaction of the bis(2‐pyridylimino)isoindole derivatives (10‐Me)‐BPI (1a), (11‐Me)‐BPI (1b), (11‐Br)‐BPI (1c), (4‐Me)‐BPI (1d) and 4‐Me‐10‐tBuBPI (1e) with [PdCl2(PhCN)2] and triethylamine in benzene gave the square‐planar palladium(II) complexes [PdCl{(10‐Me)‐BPI}] (2a), [PdCl{(11‐Me)‐BPI}] (2b), [PdCl{(11‐Br)‐BPI}] (2c), [PdCl(4‐MeBPI)] (2d) and [PdCl(4‐Me‐10‐tBuBPI)] (2e), respectively. Extraction of the crude product 2b with aqueous sodium carbonate solution led to the formation of the dinuclear carbonato‐bridged complex [{(11‐Me‐BPI)Pd}2(μ‐CO3)] (3) which was characterized by an X‐ray structure analysis. Reaction of 11‐Br‐BPI (1c) with a large excess (6 equiv.) of the acetylenes Me3SiCCH, Ph3SiCCH and PhCCH under Sonogashira conditions gave the alkynylated derivatives 11‐(Me3SiCC)‐BPI (4a), 11‐(Ph3SiCC)‐BPI (4b) and 11‐(PhCC)‐BPI (4c), which were metallated with bis(benzonitrile)dichloropalladium(II) to yield the PdII complexes [PdCl{11‐(Me3SiCC)‐BPI}] (5a), [PdCl{11‐(Ph3SiCC)‐BPI}] (5b) and [PdCl{11‐(PhCC)‐BPI}] (5c), respectively. The activity of 2b in the catalytic hydrogenation of C=C double bonds was tested for the reaction with styrene, 1‐octene and cyclohexene. The stability of the palladium complex, the reproducibility of the reaction kinetics, the different behaviour towards the three olefins chosen as substrates, as well as the possibility of isolating the non‐decomposed catalyst after several catalytic runs, provides circumstantial evidence for molecular catalysis with the BPI‐palladium complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The "bottom-up" construction of functional structures relies on the sophisticated interplay between individual structural units. [1][2][3] In most cases, the assembly of these building blocks is based on noncovalent interactions that shape extended supramolecular entities in variable dimensions. [4][5][6] Herein, well-ordered molecular patterns on surfaces are created from highly mobile precursor molecules which are transformed subsequent to their deposition and form autocomplementary species in the process. The end groups of the mobile precursors are activated by a thermally induced surfaceassisted reaction to enable intermolecular hydrogen-bonding interactions which then lead to the formation of highly ordered structures. We demonstrate control over the 2D pattern of the assembly and over the dimensionality of the aggregate by variation of the surface concentration of the precursor prior to its transformation. Furthermore, we show that the combination of resonance-assisted hydrogen-bonding [7] and the interaction of the rectangular-shaped molecules with the metal surface leads to highly robust supramolecular networks which may serve as templates for the incorporation or trapping of guest molecules.

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