Chemische Berichte p. 183 - 194 (1997)
Update date:2022-08-03
Topics:
Gauss, Christine
Veghini, Dario
Berke, Heinz
The reaction of a mixture of Fe(CO)2(PEt3)2N2 (la) and [Fe(Fe(CO)2(PEt3)2N2 (lb) with acetylene leads to three complexes: Fe(CO)2(PEt3)2N2(π:-HC=CH) (2a), Fe(CO)2(PEt3)2N2-(H)(CsCH) (2b), and Fe(CO)2(PEt3)2N2=C=CH2 (2c). Upon chromatography on silylated silica gel the mixture of 2a-c is completely transformed into 2c. The analogous reaction of la, b or of Fe(CO)2[P(O/Pr)3]2N2 (Id) with HC=CSiMe3 affords the primary oxidative addition products Fe(CO)2L2(H)(CsCSiMe3) [L = PEt3, 3a; L = P(OiPr)3, 3c]. The presence of a small amount of Al2O3 in hexane irreversibly converts 3 a and 3c into the vinylidene compounds Fe(CO)2L2=C=C(H)SiMe3[L = PEt3, 4a; L = P(OiPr)3, 4c]. The Chromatographie work-up of 4 c additionally leads to the hydrolysis product Fe(CO)2[P(O/Pr3)2]2=C=CH2 (2d). The reaction of the phosphite-substituted derivative Fe(CO)2[P-(OMe)3]2I- (le) with silylacetylene allows detection of the acetylene species Fe(CO)2(PEt3)2N2(HC=CSiMe 3) (3b), as well as the acetylido hydrido derivative Fe(CO)2[P-(OMe)3]2(H)(CsCSiMe3) (4b). In a slow subsequent process, or with promotion by Al2O3 in hexane, the vinylidene compound Fe(CO)2(PEt3)2N2=C=C(H)SiMe 3 is formed. 3b or 4b are hydrolyzed to Fe(CO)2(PEt3)2N2=C=CH2 (5c) in the presence of SiO2. The reaction of disilylacetylene with la-d results in the formation of disilylvinylidene complexes Fe-(CO)2L2=C=C(SiMe3)2 (L = PMe3, 7 a; L = PEt3, 7b; L = PiPr3, 7c). An intermediate acetylene derivative could be isolated for L = PEt3 (6 a) and spectroscopically detected for L = P(OMe)3 (6b), but could not be traced for L = P(OiPr)3. Further studies were devoted to the reactions of silyl diynes (Me3SiCsCR, R = C=CSiMe3, p-C6H4-C=CSiMe3) with la-c. In all cases the acetylene compounds Fe(CO)2L2(Me3-SiCsCR) [L = PEt3, R = CsCSiMe3, 8a; R = p-C6H4-CsCSiMe3, 9a; L = P(OMe)3, R = CSiMe3, 8b; R = p-C6H4-CsCSiMe3, 9b] were isolated, but only for 8b was an equilibrium process observed to form the corresponding vinylidene derivative Fe(CO)2[P(OMe)3]2=C=C(SiMe 3)C-C-SiMe3 (14b). lOb hydrolyzes upon chromatography on silica gel to give Fe(CO)2[P(OMe)3]2=C=CH-CsCSiMe3 (lib): Finally, the reaction of p-diethynylbenzene with la-c was explored. The acetylido hydrido species Fe(CO)2L2(H)C=C-p-C6H4-CsCH was isolated in the case of L = PEt3 (12a) and spectroscopically detected for L = P(OMe)3 (12b). 12b and 12 a transform spontaneously and in the presence of Al2O3 in hexane, respectively, to the vinylidene complexes Fe(CO)2L2=C=C(H)R [R = C6H4-C=CH, L = PEt3, 13 a; L = P(OMe)3, 13b]. 6a, 7a, and 8a have been characterized by single-crystal X-ray diffraction studies. VCH Verlaegsgesellschaft mbH,.
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