Avelina Arnanz

Synthesis and electrochemical study of cobalt carbonyl complexes of trimethylsilyl-substituted 1,3,5-triethynylbenzene

Treatment of 1,3,5-tris(trimethylsilylethynyl)benzene or 1,3,5-triethynylbenzene with Co 2 (CO) 8 or Co 2 (CO) 6 (dppm) produced the formation of substituted ethynylcobalt complexes with one, two or three Co 2 (CO) 6 or Co 2 (CO) 4 (dppm) units, [{X 3 (Co 2 (CO) 6 )C 2 } n (XCC) m (1,3,5-C 6 H 3 )] (X=H or SiMe 3 ) ( n =1, 2 or 3; m =3− n ) and [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 } n (SiMe 3 CC) m (1,3,5-C 6 H 3 )] ( n =1 or 2; m =3− n ), in a high yield. Desilylation of the non-metallated alkynes in [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 }(SiMe 3 CC) 2 (1,3,5-C 6 H 3 )] occurred on treatment with KOH. Electrochemical results provide evidence for communication between the C 2 Co 2 centres. Crystals of [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 } 2 (SiMe 3 CC)(1,3,5-C 6 H 3 )] suitable for single-crystal X-ray diffraction were grown and the molecular structure of this compound is discussed.

SYNTHESIS AND CHARACTERIZATION OF NEW TRANSITION METAL DIYNYL COMPLEXES

The reaction of (η 5 -C 5 H 5 )Mo(CO)(dppe)Cl with LiCCCCSiMe 3 yielded (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCSiMe 3 ( 1b ) and, as a by-product (η 5 -C 5 H 5 )Mo(CO)(dppe)Br ( 1a ). Treatment of 1b with 0.2 equivalents of tetrabutylammonium fluoride or (η 5 -C 5 H 5 )Mo(CO)(dppe)Cl with HCCCCH gave the terminal butadiyne complex (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCH ( 2 ). Complex 2 was deprotonated with sec -BuLi or lithium diisopropylamide, and the resulting anion (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCLi ( 3 ) was trapped with Me 3 SiCl to regenerate 1b . The synthesis of Co 2 (CO) 4 L 2 (μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) (L 2 =dppa 4 , 2PPh 2 Me 5 ) compounds can be achieved by two methods: from Co 2 (CO) 6 (μ-dppa) by reaction with Me 3 SiCCCCSiMe 3 in 1:1 ratio to yield 4 , or from Co 2 (CO) 6 (μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) by reaction with dppa (1:1 ratio) and PPh 2 Me (1:2 ratio) to yield 4 and 5 , respectively. When the Co 2 (CO) 4 (μ-dppa)(μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) complex was treated with more Co 2 (CO) 6 (μ-dppa) the green di-substituted complex [Co 2 (CO) 4 (μ-dppa)] 2 (μ-η 2 :μ-η 2 -Me 3 SiC 2 C 2 SiMe 3 ) ( 6 ) was obtained. Desilylation of 4 with Bu 4 NF gave Co 2 (CO) 4 (μ-dppa)(μ-η 2 -Me 3 SiC 2 CCH) ( 7 ). All compounds synthesized have been characterized by analytical and spectroscopic data (IR, 1 H-, 31 P-, 13 C-NMR, MS). In addition, compounds 1a and 4 were characterized by X-ray structure analysis.

Comparative reactivity study of cyclopentadienyl and fulvalene molybdenum complexes

The reactions of cis-1,1%-[h 5 :h 5 -(C5H3CO2Me)2]Mo2(CO)6 (1), in the presence of 1 equiv. of Me3NO, and [(h 5 C5H4CO2Me)Mo(CO)3]2 (2) with dppe produce CO labilization and formation of the dinuclear zwitterions trans-1,1%-[h 5 :h 5 (C5H3CO2Me)2]Mo2(CO)5(dppe) (3) and disproportionation species [(h 5 -C5H4CO2Me)Mo(CO)2(dppe)] [(h 5 -C5H4CO2Me)Mo(CO)3] (4), respectively. Using the same method, the reactions of trans-1,1%-[h 5 :h 5 -(C5H3CO2Me)2]Mo2(CO)6I2 and (h 5 C5H4CO2Me)Mo(CO)3I with PPh3 in the presence of 1 and 2 equiv. of Me3NO yield trans-1,1%-[h 5 :h 5 -(C5H3CO2Me)2]Mo2(CO)4(PPh3)2I2 (5) and (h 5 -C5H4CO2Me)Mo(CO)2(PPh3)I (6). The reactions of the several anionic carbonyl species {trans1,1%-[h 5 :h 5 -(C5H3CO2Me)2]Mo2(CO)6} 2 ,[ ( h 5 :h 5 -C10H8)W2(CO)6] 2 and [(h 5 -C5H4CO2Me)Mo(CO)3] with S2Ph2 give rise to the thiolate‐fulvalene complexes cis-1,1%-[h 5 :h 5 -(C5H3CO2Me)2]Mo2(CO)4(m-SPh)2 (7) and (h 5 :h 5 -C10H8)W2(CO)6(SPh)2 (8) and the thiolate-bridged dimer [(h 5 -C5H4CO2Me)Mo(CO)(m-SPh)]2 (9). Treatment of 6 with 1 equiv. of HCCCCH and with (h 5 -C5H5)Mo(CO)(dppe)(CCCCH), in the presence of CuI at room temperature, afford the cyclopentadiene complexes (h 5 -C5H4CO2Me)Mo(CO)2(PPh3)(CCCCH) (10 )a nd ( h 5 -C5H4CO2Me)(PPh3)(CO)2Mo(CCCC)Mo(CO)(dppe)(h 5 -C5H5) (11), respectively. The reaction of (h 5 -C5H5)Mo(CO)(dppe)(CCCCH) with Co2(CO)8 yields [Co2{m-HC2CC[Mo(CO)(dppe)(h 5 -C5H5)]}(CO)6 ]( 12). All the new compounds have been characterized by analytical and spectroscopic methods.