Stefan Gebert

Cyclopentadienyl) metal cluster complexes of the group 9 transition metals

Abstract Cluster complexes with metal frameworks built from [(C5R5)(d9-M)] units are reviewed (d9−M = Co, Rh, Ir). The range of additional ligands which may be attached to the [(C5R5)M]n cores includes main group atoms such as H, O, S and Se, small inorganic molecules such as CO, CS, NO and NH as well as organic compounds such as isocyanides, alkynes, alkylidynes, arenes and others. Syntheses, structures and reactivities of the known cluster complexes of this type are discussed. Special emphasis is given to the relationship of structure and chemical properties to the valence electron count in systems of similar composition.

Tetracobalt Complexes with Co3 Face-Capping Cycloheptatrienyl and Cyclooctatetraene Ligands

The novel tetracobalt cluster complexes1 and 2, which contain facial CnHn ligands, have been synthesized and their crystal structures determined. The apical C8H8 ligand can be selectively substituted by a number of other ligands. In the solid state, the hydrogen atoms of the cycloheptatrienyl and cyclooctatetraene ligands take part in intra- and intermolecular hydrogen-bonding interactions of the C−H⋅⋅⋅O type.

Transformation of cyclohexadiene on an Fe3P frame: cluster complexes with hexadiene, cyclohexadiene and arene ligands

Abstract UV photolysis of the phosphinidine-bridged cluster complex [Fe 3 (CO) 9 (H) 2 (P t Bu)] ( 9 ) in the presence of 1,3-cyclohexadiene gives the complex [Fe 3 (CO) 8 (η 4 -1,3-cyclohexadiene)(μ 3 -P t Bu)] ( 13 ) in 20% yield. As a side-reaction, hydrogenolysis of cyclohexadiene occurs to give the complexes [Fe 3 (CO) 8 (2-5-η-2,4-hexadiene)(μ 3 -P t Bu)] ( 14 ) and [Fe 3 (CO) 8 (1-4-η-1,3-hexadiene)(μ 3 -P t Bu)] ( 15 ) in about 5% yield each. The crystal and molecular structures of 13 , 14 and 15 were determined. The (cyclo)hexadiene ligands are bonded to the Fe 3 P clusters in the apical coordination mode; of the carbonyl ligands two are semi-bridging. The composition [Fe 3 (μ 2 -H)(CO) 7 (μ-1-3-η:4,5-hexadienyl)(μ 3 -P t Bu)] ( 16 ) is tentatively assigned to a fourth product (2% yield), based on IR and NMR spectroscopic data. On heating to 80°C, a mixture of the complexes 14 and 15 is quantitatively converted into 16 . Complex 13 is also formed in lower yield (15%) from [Fe 3 (CO) 10 (P t Bu)] ( 10 ) and 1,3-cyclohexadiene in a thermal reaction. UV irradiation of complex 13 in benzene solution gives [Fe 3 (CO) 7 (η-C 6 H 6 )(μ 3 -P t Bu)] ( 18a ) in low yield. In toluene, a 3:7 mixture of 18a and [Fe 3 (CO) 7 (η-C 6 H 5 Me)(μ 3 -P t Bu)] ( 18b ) is obtained, proving the dehydrogenation of the cyclohexadiene ligand in 13 to give an η 6 -benzene. The apical (η 6 -) coordination of the toluene ligand in 18b is confirmed by a crystal structure analysis, which also shows the presence of a face-capping carbonyl ligand.

Facial coordination of cyclooctatetraene to a Co2Ni triangle in a heterometallic trinuclear cluster complex

Reaction of [(η-C 5 H 5 )NiCo 3 (CO) 9 ] ( 5 ) with 1,3,5,7-cyclooctatetraene or 1,4-(SiMe 3 ) 2 C 8 H 6 , respectively, yields the complexes [Co 2 Ni(CO) 6 (μ 3 -η 8 -C 8 H 6 R 2 )] (R=H, SiMe 3 ) ( 7a , b ). Dramatic modifications of the tetrametallic cluster core and the ligand sphere of 5 to give the trinuclear complex 7 are driven by the preference of the cyclopolyenes for facial (μ 3 -η 8 ) coordination. The title complexes are the first examples of facial cyclooctatetraene coordination to a heterometallic (Co 2 Ni) triangle.

Dynamics and molecular aggregation in crystalline [{M(C5H5)}3(µ3-η2 : η2 : η2-C6H5R)][M = Co, R = CH(Ph)Me, CH2CH2Ph or CHCHMe; M = Rh, R = H] clusters

The intermolecular aggregation in crystalline arene clusters of the type [{M(C5H5)}3(µ3-η2 : η2 : η2-C6H5R)][M = Co, R = CH(Ph)Me, CH2CH2Ph or CHCHMe; M = Rh, R = H] has been investigated by atom–atom packing potential-energy calculations and computer graphics. The ease of reorientation of the arene fragments and of the cyclopentadienyl ligands in the solid state has been investigated by calculating intramolecular and intermolecular potential-energy barriers. It has been shown that, except for the benzene ligand in [{Rh(C5H5)}3(µ3-η2 : η2 : η2-C6H6)], the facial arenes cannot undergo reorientation in the solid state, whereas the reorientational motion of the cyclopentadienyl ligands is under intramolecular control.

Synthesis and X-ray structure of a cluster complex with facial coordination of cyclooctatetraene to a Co2Ni triangle

The reaction between [(η-C5H5)NiCo3(CO)9] and cyclooctatetraene yields [Co2Ni(CO)6(µ3-η2:η3:η3-C8H8)] with a cyclooctatetraene ligand in the facial coordination mode to a heterometallic Co2Ni triangle.

C–H · · · OHydrogen bonding in crystalline complexes carrying methylidyne(µ3-CH) and methylene (µ-CH2) ligands: adatabase study

The relationship between the molecular and crystal structures of organometallic complexes carrying methylidyne (µ 3 -CH) and methylene (µ-CH 2 ) ligands has been investigated on data retrieved from the Cambridge Structural Database. It has been shown that µ 3 -CH and µ-CH 2 groups participate in intermolecular hydrogen-bonding networks of the C–H · · · O type involving, in most cases, the oxygen atoms of CO ligands as acceptors. The order of decreasing acidity, judged on purely geometrical grounds from the average length of the hydrogen-bonding interactions, is roughly µ 3 -CH > µ-CH 2 . These ligands establish C–H · · · O interactions which are comparable in length to those established by hydrogen atoms bound to sp- and to sp 2 -hybridized carbon atoms consistent with experimental and theoretical evidence.