Simon Lotz

Synthesis, characterization and decomposition patterns for thienylene bridged dinuclear biscarbene complexes of manganese and chromium in refluxing carbon disulphide and acetone

Abstract The dinuclear complexes [ML3(CO)2{C(OEt)C4H2SC(OEt)}M(CO)2L3] (M=Cr, L=CO 1; M=Mn, L3=η5-C5H4R, R=H 2 and Me 3) were synthesized from dilithiated thiophene according to the Fischer-method. The highly reactive biscarbene complexes are unstable in acetone and react to afford [ML3(CO)2{C(OEt)C4H2SC(O)OEt] (M=Cr 4, M=Mn, R=H 5 and Me 6). When refluxed in carbon disulphide, 1 affords as the only isolable product 4, whereas 2 and 3, in addition to 5 and 6, reacts with CS2 to give the thiono ester compounds [Mn(η5-C5H4R)(CO)2{C(OEt)C4H2SC(S)OEt}] with R=H 7 and Me 8, respectively. Compound 1 crystallizes in the monoclinic space group C2/c with a=21.593(12), b=10.235(3), c=22.531(12) A, β=92.06(4)° and Z=8.

Synthesis and crystal structures of carbene complexes with conjugated thiophene units

Abstract Binuclear carbene complexes of chromium and tungsten containing a conjugated thiophene spacer, dithieno[3,2- b :2′,3′- d ]thienylene (TTT), were synthesized according to the Fischer method for the synthesis of carbene complexes. Biscarbene complexes of the type [(CO) 5 M{C(OEt)TTTC(OEt)}M(CO) 5 ] (M=Cr, 2 ; W, 5 ) were afforded together with the corresponding monocarbene complexes [M{C(OEt)TTTH}(CO) 5 ] (M=Cr, 1 ; W, 4 ) and decomposition products [M{C(OEt)TTTC(O)OEt}(CO) 5 ] (M=Cr, 3 ; W, 6 ), formed in the reaction of the biscarbene complexes with trace amounts of oxygen. X-ray crystallographic determinations were performed on compounds 1 , 2 and 6 to assess the influence of the different substituents in the C9 position of the TTT carbene complexes on the structural features of the condensed rings. The crystallographic data of these three complexes are reported in this paper.

Chromium and Tungsten Carbene Complexes of Thieno[3,2-b]thiophene

Dinuclear carbene complexes with 3,6-dimethylthieno[3,2-b]thienylene (T′T′) and thieno[3,2-b]thienylene (TT) spacers were prepared using the classical Fischer method. Their reactivity in solution towards oxygen, as well as their structural features were investigated. Chromium and tungsten carbene complexes were synthesized via dilithiation of the thienothiophene, followed by the addition of the appropriate metal carbonyl complex and subsequent alkylation with triethyloxonium tetrafluoroborate. Monocarbene [M{C(OEt)T′T′H}(CO)5], (M = Cr, 1; W, 4), biscarbene [(CO)5M{C(OEt)T′T′C(OEt)}M(CO)5], (M = Cr, 2; W, 5), and the products [M{C(OEt)T′T′C(O)OEt} (CO)5], (M = Cr, 3; W, 6), where a metal moiety of 2 and 5 has been replaced by an ester functionality, were isolated. The reaction product afforded in the reaction of Cr(CO)6 with lithiated thieno[3,2-b]thiophene, [Cr{C(OEt)TTC(O)Bu}(CO)5], 7, did not resemble any of the products isolated in the similar reaction of Cr(CO)6 with lithiated 3,6-dimethylthieno[3,2-b]thiophene.

Rhenium ethoxy- and hydroxycarbene complexes with thiophene substituents

Reaction of mono- and dilithiated thiophene (a), bithiophene (b) and 2,5-dibromothiophene (c) with [Re(2)(CO)(10)] afforded, after subsequent alkylation with triethyloxonium tetrafluoroborate, tetra- and binuclear Fischer carbene complexes, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)X}], n = 1, X = H (1a); n = 2, X = H (1b); n = 1, X = Br (1c); n = 1, X = C(OEt)Re(2)(CO)(9), (2a); n = 2, X = C(OEt)Re(2)(CO)(9) (2b), as major products. The dirhenium acylate intermediates from this reaction not only gave the expected novel ethoxycarbene complexes with alkylation but after rhenium-rhenium bond breaking afforded a number of minor products. The (1)H NMR spectrum of the crude reaction mixture revealed the formation of four metal hydride complexes and aldehydes. Protonation with HBF(4) instead of alkylation with Et(3)OBF(4) significantly increased the yields of the hydride complexes, which enabled the positive identification of three of these complexes. In addition to the known compounds [Re(CO)(5)H] and [Re(3)(CO)(14)H] (3), a unique complex displaying a hydroxycarbene fragment connected to an acyl fragment via an O-H···O hydrogen bond and a Re···H···Re bond linking the two Re centers, [(μ-H){Re(CO)(4)C(OH){C(4)H(2)S}(n)H}{Re(CO)(4)C(O){C(4)H(2)S}(n)H}], n = 1 (4a) or n = 2 (4b), were isolated. The formation of thiophene aldehydes, H{C(O)}(m){C(4)H(2)S}(n)C(O)H (m = 0 or 1 and n = 1 or 2), were observed and the novel monocarbene complexes with terminal aldehyde groups, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)C(O)H}], n = 1 (5a) and n = 2 (5b) could be isolated. A higher yield of 5b was obtained after stirring crystals of 2b in wet THF. The crystal structures of 1a, 2a, 4a and 5b are reported.

Thiophene decorated with Fischer carbene ligands

The activation of a section, or of all the carbons of thiophene by bromine in lithium-halogen exchange reactions, was implemented in a step-wise manner to facilitate the preparation of novel multiple Fischer carbene-bearing thiophene compounds.

Iron carbene complexes. Part 3. Aminolysis of di-iron alkoxycarbene complexes with ammonia and dimethylamine. X-Ray crystal structure of [Fe2(µ-SPh)2(CO)5{C(NMe2)Ph}]

Reaction of the mercapto-bridged di-iron carbene complexes [(OC)3Fe(µ-SPh)2Fe(CO)2{C(OEt)Ph}] and [(OC)3Fe{µ-S(CH2)3S}Fe(CO)2{C(OEt)Bu}] with ammonia and dimethylamine afforded the aminocarbene complexes, [(OC)3Fe(µ-SPh)2Fe(CO)2{C(NR4R5)Ph}](R4,R5= H or Me) and [(OC)3Fe{µ-S(CH2)3S}Fe(CO)2{C(NR4R5)Bu}](R4,R5= H or Me). Competitive to the aminolysis reaction is substitution of the carbene ligand by an amine. The structure of [(OC)3Fe(µ-SPh)2-Fe(CO)2{C(NMe2)Ph}] was confirmed by X-ray crystallography. The crystals are monoclinic, space group P21/n with a= 9.987(3), b= 18.955(5), c= 14.557(3)A, β= 107.74(2)°, and Z= 4. The carbene ligand is in the trans position to the iron–iron bond and the phenyl groups of the bridging sulphur atoms are in an anti orientation.

Synthesis and structure of 4,6-disubstituted dibenzothiophenes and their use in the preparation of binuclear platinum(II) complexes

The reaction of two equivalents of [Pt(PEt3)4] with 4,6-dibromodibenzothiophene (DBT-Br2) afforded trans,trans-[(μ-DBT-1κC4:2κC6){PtBr(PEt3)2}2] (5), a unique example of double oxidative addition of a heteroaromatic substrate to Pt(0). The related bimetallic Pt(II) complex, cis,cis-[(μ-DBT-1κC4:2κC6){Pt(η4-cod)Cl}2] (6), was isolated via a double transmetallation of 4,6-bis(trimethylstannyl)dibenzothiophene with [Pt(η4-cod)Cl2], where cod is 1,5-cyclooctadiene. The new complexes were characterised by spectroscopic techniques. The disubstituted dibenzothiophene compounds were prepared by dilithiation of dibenzothiophene, followed by quenching with chlorotrimethylsilane and chlorotrimethylstannane, to give 4,6-(SiMe3)2(SC12H6) (2) and 4,6-(SnMe3)2(SC12H6) (4), respectively. Treatment of 4,6-(SiMe3)2(SC12H6) with bromine produced 4,6-Br2(SC12H6) (3). The X-ray crystal structures of 2 and 3 were determined. An improved method of synthesis of 2,8-dibromodibenzothiophene (1) was also developed.

Trimethylstannane derivatives of cobalt(I); synthesis and NMR spectroscopy. The crystal structures of [Co(Me3Sn)(CO)3L] (L = PPh3, AsPh3)

Abstract The Na/Hg reductive cleavage of the cobaltcobalt bond in CO2(CO)6L2 (L = PPh3 P(OPh)3 AsPh3) and subsequent reaction with Me3SnCl, afforded the five coordinate complexes Co(Me3Sn)(CO)3L (L = PPh3, P(OPh)3, AsPh3). The intermediate sodium salts Na[CO(CO)3L] are unstable and were not isolated. The 31P, 119Sn, 13C and 1H NMR spectra were recorded and are discussed. Crystal structure analyses of [Co(Me3Sn) (CO)3L] (L = PPh3, AsPh3) revealed, in both cases, a trigonal bipyramidal geometry with the trimethyl tin and the triphenyl phosphine/arsine in the two axial positions.

Ferrocenyl ligands in mixed valence high-oxidation state rhenium complexes

Abstract The reactions of the ferrocenyl ligands dppf and dfed with [ReO(PPh 3 ) 2 Cl 3 ] afforded the complexes [ReO( dppf - P , P ′)Cl 3 ] ( 1 ), which has a cis – fac arrangement of ligands, and [ReO 2 ( dfed - N , N ′) 2 ] + ( 3 ) ( dppf =1,1′-bis(diphenylphosphino)ferrocene and dfed =bis( N , N ′-ferrocenylmethyl)ethylenediamine). In wet ether, 1 converts into [ReO( dppf - P , P ′)(OH)Cl 2 ] ( 2 ). Crystal structure determinations were performed on 1 and the tetraphenylborate salt of 3 . Compound 1 crystallizes in the orthorhombic system, space group P 2 1 2 1 2 1 with a =11.5364(2), b =15.8381(4) and c =17.5050(4) A and 3 crystallizes in the orthorhombic system, space group Aba 2 with a =15.3773(8), b =15.1344(7) and c =28.2817(14) A.

Di-tungsten Bis-carbene Complexes Linked by Condensed Heteroaromatic Spacers

The 2,7-dilithiated substrates of 3,6-dimethylthieno[3,2-b]thiophene, N,N′-dimethylpyrrolo[3,2- b]pyrrole and N-methylthieno[3,2-b]pyrrole were reacted with W(CO)6 to give, after subsequent alkylation with Et3OBF4, the ditungsten biscarbene complexes [(CO)5W{C(OEt)XXC(OEt)} W(CO)5] (XX = condensed heteroaromatic spacers). Sites of attack during the dilithiation of the condensed rings were studied and compared, and the yields of the desired ditungsten biscarbene complexes optimized by changing the reaction conditions according to the role of the heteroatoms in the rings. The crystallographic data of the three ditungsten biscarbene complexes are reported and their structural features compared. The methyl substituents on the condensed heteroaromatic rings play an important role in determining the molecular configurations.