Towards Understanding the Reactivity and Optical Properties of Organosilicon Sulfide Clusters.

We report the extension of the class of organotetrel sulfide clusters with further examples of the still rare silicon-based species, synthesized from RSiCl3 with R=phenyl (Ph, I), naphthyl (Np, II), and styryl (Sty, III) with Na2 S. Besides known [(PhSi)4 S6 ] (IV), new compounds [(NpSi)4 S6 ] (1) and [(StySi)4 S6 ] (2) were obtained, the first two of which underwent reactions with [AuCl(PPh3 )] to form ternary complexes. DFT studies of cluster dimers helped us understand the differences between the habit of {Si4 S6 }- and {Sn4 S6 }-based compounds. Crystalline 1 showed a pronounced nonlinear optical response, while for intrinsically amorphous 2, the chemical damage threshold seems to inhibit a corresponding observation. Calculations within the independent particle approximation served to rationalize and compare electronic and optical excitations of [(RSi)4 S6 ] clusters (R=Ph, Np). The calculations reproduced the measured data and allowed for the interpretation of the main spectroscopic features.

Variations in the Interplay of Intermetallic and Metal Chalcogenide Units in Organotin-Copper Selenide Clusters.

We report the formation and structures of two new organotin-copper selenide clusters that were obtained in a two-step procedure. First, [(R1Sn)4Se6] [R1 = CMe2CH2C(O)Me] is reacted with [Cu(PPh3)3Cl] and (SiMe3)2Se to form a bright-orange powder, the nature of which could not be identified in detail, yet a suspension of it in CH2Cl2 reacts with N2H4·H2O to afford single crystals of two cluster compounds, either [(Cu3Sn){(R2Sn)2Se4}2{(R2Sn2)Se3}] (1) or [(N2H4)(Cu4Sn){(R2Sn)2Se4}3] [2; R2 = CMe2CH2C(NNH2)Me]. Both are based on an intermetallic CuxSn cluster core (x = 3, 4), which is surrounded by organotin selenide units in different fashions. The results foster the assumption of a complex equilibrium to be present in according reaction mixtures.

Organotin Selenide Clusters and Hybrid Capsules.

Several compounds with unique structural motifs that have already been known from organotin sulfide chemistry, but remained unprecedented in organotin selenide chemistry so far, have been synthesized. The reaction of [(R1 Sn)4 Se6 ] (R1 =CMe2 CH2 C(O)Me) with N2 H4 ⋅H2 O/(SiMe3 )2 Se and PhN2 H3 /(SiMe3 )2 Se led to the formation of [{(R2 Sn)2 SnSe4 }2 (µ-Se)2 ] (1; R2 =CMe2 CH2 C(Me)NNH2 ) and [{(R3 Sn)2 SnSe4 }2 (µ-Se)2 ] (2; R3 =CMe2 CH2 C(Me)NNPhH)). The addition of ortho-phthalaldehyde to [(R2 Sn)4 Se6 ] yielded a cluster with intramolecular bridging of the organic groups, namely, [(R4 Sn2 )2 Se6 ] (3; R4 =(CMe2 CH2 C(Me)NNCH)2 C6 H4 ). The introduction of organic ligands with longer chains finally allowed the isolation of inorganic-organic capsules of the type [(µ-R)3 (Sn3 Se4 )2 ]X2 , with R=(CMe2 CH2 C(Me)NNHC(O))2 (CH2 )4 and X=[SnC3 ], Cl (4 a, b) or R=CMe2 CH2 C(Me)NNH)2 and X=[SnCl3 ] (5). The capsules enclose solvent molecules and/or anions as guests. All compounds were characterized by means of single-crystal X-ray diffraction studies, NMR spectroscopy, and mass spectrometry.

Metal-ligand cooperation in H2 activation with iron complexes bearing hemilabile bis(diphenylphosphino)amine ligands.

The octahedral transition-metal complex [(dppa)Fe(Ph2P-N-PPh2)2] (1) [dppa = bis(diphenylphosphino)amine] with homofunctional bidentate ligands is described. The ligand exhibits hemilability due to its small bite angle and the steric repulsion of the coordinated donor groups. As the {Ph2P-N-PPh2}(-) ligand can act as an internal base, heterolytic cleavage of dihydrogen by complex 1 leads to the formation of the hydride complex [(dppa)(Ph2P-N-PPh2)Fe(H)(κ(1)-Ph2P-NH-PPh2)2] (2), representing an example of cooperative bond activation with a homofunctional hemilabile ligand. This study demonstrates that hemilability of homofunctionalized ligands can be affected by careful adjustment of geometric parameters.

Formation of an iron phosphine-borane complex by formal insertion of BH3 into the Fe-P bond.

A unique hydrido phosphine-borane iron(II) complex [(dppa)(Ph2P-N-P(BH3)Ph2)Fe(H)] (1) was obtained by the reaction of iron(II) chloride and two equivalents of bis(diphenylphosphino)amine (dppa) with an excess of sodium borohydride in acetonitrile-ethanol mixtures. Detailed investigations of the reaction revealed that a mixture of cis- and trans-[(dppa)2Fe(NCMe)2]²âº is formed prior to the reduction by sodium borohydride. Depending on the solvent, different products were obtained by the reduction: in acetonitrile-ethanol mixtures the hydrido phosphine-borane complex 1 is formed by formal insertion of BH3, while the reduction in pure acetonitrile results in the formation of the cationic complex trans-[(dppa)2Fe(H)(NCMe)](BH4) (4). Complex 4 is remarkably stable in ethanol and does not undergo phosphine-borane formation, even in the presence of excess sodium borohydride. This observation suggests that the phosphine-borane complex is generated by the reaction with the first equivalent of sodium borohydride with the participation of ethanol, followed by deprotonation or dihydrogen elimination. Experiments with similar diphosphine ligands, such as bis(diphenylphosphino)methane, did not yield a phosphine-borane complex, indicating the crucial role of the amine group in the observed reactivity.