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Syntheses of Halogenated Ethenyl Isocyanide Chromium Complexes as Organometallic Precursor Molecules for Ethenyl and Ethynyl Isocyanides
Author(s) -
BalboBlock Marco,
Bartel Christoph,
Lentz Dieter,
Preugschat Dagmar
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010216)7:4<881::aid-chem881>3.0.co;2-2
Subject(s) - chemistry , isocyanide , medicinal chemistry , nucleophile , phosphorane , triple bond , trimethylsilyl , substituent , diethyl ether , stereochemistry , double bond , organic chemistry , catalysis
The radical alkylation of tetraethylammonium pentacarbonyl(cyano)chromate 1 yielded the halogenated ethyl isocyanide complexes [(CO) 5 Cr(CN−CClX−CClYF)] 3 ( a , X=Cl, Y=F; b , X=F, Y=F and c , X=Y=Cl). Dehalogenation of 3 using zinc in diethyl ether gave [(CO) 5 Cr(CN−CX=CFY)] 4 . The compounds 4 a, b reacted with various nucleophiles exclusively at the difluoromethylene group. The unstable phosphorane 5 , which is formed on reaction of 4 b with trimethylphosphane, decomposed thermally and on hydrolysis yielding pentacarbonyl(1,2‐difluoroethenyl isocyanide)chromium ( 6 ). The cyano substituent can be introduced in the β position of the isocyanide function by reaction of 4 a , b with potassium cyanide, leading to the formation of [(CO) 5 Cr(CN−CX=CF−CN)] ( 7 ). Reactions of 4 a, b with organolithium or organomagnesium compounds yielded [(CO) 5 Cr(CN−CX=CF−R)] ( 8 ) and [(CO) 5 Cr(CN−CF=CF−C≡C−CF=CF−NC)Cr(CO) 5 ] ( 10 ). The trimethylsilyl group in 8 a , b , d could be removed by a solution of potassium carbonate in methanol leading to [(CO) 5 Cr(CN−CX=CF−C n −H)] ( 11 ) ( n =2, 4). Octacarbonyldicobalt reacted with 8 e under coordination of the C−C triple bond to the hexacarbonyldicobalt fragment, resulting in the cluster compound 12 . The crystal and molecular structure of 8 i, 11 a , b , and 12 were elucidated by X‐ray crystallography. The alkenyl and alkynyl isocyanides CN−CCl=CF 2 ( 13 a ), CN−CF=CF 2 ( 13 b ), CN−CCl=CClF ( 13 c ), CN−CF=CFH ( 14 ), CN−CC−H ( 15 ), CN−CC−CN ( 16 ), and CN−CCl=CF−CN ( 17 ) were obtained by flash vacuum pyrolysis of 4 a, 4 b, 4 c, 6 , and 7 a , respectively.