Matthias Lutz

Cooperative reactivity of early-late heterodinuclear transition metal complexes with polar organic substrates

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.

Metal–Metal Bonds between Group 12 Metals and Tin: Structural Characterization of the Complete Series of Sn-M-Sn (M=Zn, Cd, Hg) Heterodimetallic Complexes

Reaction of the lithium triamidostannate [MeSi[SiMe(2)N(p-Tol)](3)SnLi(OEt(2))] (1) with 0.5 molar equivalents of MCl(2) (M=Zn, Cd, Hg) in toluene afforded the corresponding heterodimetallic complexes [MeSi[SiMe(2)N(p-Tol)](3)Sn](2)M [M=Hg (2), Cd (3), and Zn (4)]. The molecular structures of the mercury and cadmium complexes were determined by X-ray diffraction and found to adopt a linear Sn-M-Sn metal-metal bonded array (d(Sn-Hg) 2.6495(2), d(Sn-Cd) 2.6758(1) A), these being the first Hg-Sn and Cd-Sn bonds to be characterized by X-ray diffraction. That the Hg-Sn bonds are shorter than the Cd-Sn bonds in the isomorphous complexes is attributed to relativistic effects in the mercury system. In contrast, the structure of the Zn analogue is unsymmetrical with one stannate unit being Sn-Zn bonded (d(Sn(1)-Zn) 2.5782(4) A), while the Zn(II) atom bridges two amido functions of the second stannate cage, thus representing a second isomeric form of these complexes. The different degree of metal-metal bond polarity is reflected in the (119)Sn NMR chemical shifts of the three complexes. Variable-temperature NMR studies and a series of (1)H ROESY experiments of the cadmium complex 3 in solution revealed a dynamic exchange between the two isomers.

A Tripodal Triaminostannate as a Metal Nucleophile: Synthesis of Transition Metal−Tin Heterodimetallic Complexes

The coordination capability of the previously reported triamidostannate [MeSi{SiMe2N(4-CH3C6H4)}3SnLi(OEt2)] (1) as a precursor for transition metal−tin heterodimetallic complexes is presented. Whereas reaction with CH3I, Me3SiCl, or Me3SnCl yielded the derivatives [MeSi{SiMe2N(4-CH3C6H4)}3Sn−R] (R = Me, 2; Me3Si, 3; Me3Sn, 4), demonstrating the nucleophilic properties of the stannate(II), its complexation to transition metal centres was achieved by halide substitution with [CuCl(PPh3)]4, [CpM(CO)2X] (M = Fe, X = Cl; M = Ru, X = Br), [CpM(CO)3Cl] (M = Mo, W) and trans(Cl)-[RuCl2(bpy)(CO)2] to give [MeSi{SiMe2N(4-CH3C6H4)}3Sn−Cu(PPh3)] (5), [MeSi{SiMe2N(4-CH3C6H4)}3Sn− M(CO)2Cp (M = Fe: 6; Ru: 7)], [MeSi{SiMe2N(4-CH3C6H4)}3Sn−M(CO)2Cp] (M = Mo: 8; W: 9) and [(MeSi{SiMe2N(4-CH3C6H4)}3Sn)2Ru(bpy)(CO)2] (10), of which 6, 9 and 10 were characterized by X-ray diffraction.

Lithium cation solvation in the ligand periphery of an ortho-fluorophenyl substituted tripodal triaminostannate

Abstract The trilithium triamide [HC{SiMe2NLi(2-FC6H4)}3] (2) was obtained by treatment of HC{SiMe2NH(2-FC6H4)}3 (1) with 3 M equivalents of n-butyllithium in n-pentane. Upon reaction of 2 with 1 M equivalent of SnCl2 in toluene at elevated temperature, the amidostannate [HC{SiMe2N(2-FC6H4)}3 SnLi] (3) was formed for which an X-ray diffraction study established the intramolecular coordination of the lithium cation by two of the peripheral ortho-fluoro groups. The mean LiF bond distances found in 3 are 1.986(8) and 1.982(9) A for the two independent molecules in the asymmetric unit. This exposed position of the lithium, bonded to two amido N atoms and the two fluorine atoms, leads to a very close contact with the adjacent methyl-group [d(Li1C3)=2.545 and 2.516 A for the two independent molecules in the unit cell] which effectively occupies a vacant coordination site of the lithium centre. This disposition of the alkyl group at close proximity of the Li centre is probably due to the unusual cation coordination geometry (distorted square-planar instead of tetrahedral) imposed by the rigid caged structure of the triamidoatannate(II).