Borkomplexe von Malonsäureamiden und Malonsäureamidinen

Abstract

Boron Complexes of Malonamides and MalonamidinesN,N,N',N'-Tetrarnethylmalonamide (4) reacts with triethyloxonium tetrafluoroborate in boiling tetrachloroethane or with diethyl ether -boron trifluoride at room temperature to form the tetrafluoroborate 6 a which was deprotonated with triethylamine to give 4,6-bis(dimethylamino)-2,2-difluoro-3-oxa-l-oxonia-2-borata-4,6-cyclohexadiene (7). With 4 and boron trichloride in CCI, the neutral complex 9 is obtained, in CH2C12 the chelate complex 10. Similar to diethyl ether -boron trifluoride (2-aminoethoxy)diphenylborane (12) and triethylborane (15) condense with 4 to yield the salts 13 and 17, respectively, and the neutral complexes 14 and 16, respectively. N,N,N",N"- Die Bildung von Koordinationsverbindungen des Bors rnit &Diketonen wurde 1905 erstmals von Dilthey und Mitarb. ') beobachtet. Sie erhielten aus Bortrichlorid und Acetylaceton den Borchelat-Komplex 1. Anders als Bortrichlorid verhalt sich Bortrifluorid, das rnit Acetylaceton den Borkomplex 2 liefert*). In der Folgezeit sind zahlreiche weitere Borkomplexe von fi-Diketonen, Acetessigsaurederivaten3-5 ) , P-Ketoiminen 6 -7 ) , N-Acylamiden ' ), N-Acylamidinen" und Biguanidinen") erhalten worden. Allen gemeinsam ist vierbindiges Bor rnit einer formalen negativen Ladung und ein Koordinationspartner der allgemeinen Struktur 3 aus 5 Atomen und 6 n-Elektronen mit einer formalen positiven Ladung. Einen Uberblick uber diese Verbindungstypen gibt Mikhailoti ' I ) .berichten, da13 sie rnit Malonsaureestern keine Borkomplexe erhalten haitten. Auch andere Malonsaurederivate sind unseres Wissens bisher noch nicht rnit Erfolg auf diesem Gebiet eingesetzt worden.

Structural studies of organoboron compounds. XXXIV. 4-(N-Methoxymethylimino)-2,2-diphenyl-1,3-dioxa-2-borata-1,2,3,4-tetrahydronaphthalene and 4-diethylimino-2,2-diphenyl-1,3-dioxa-2-borata-1,2,3,4-tetrahydronaphthalene

“…The C(3&C(4) and C ( 5 ) 2 ( 6 ) bonds (1.369-1.378 A) are shorter than the C(2&C(3), C ( 2 ) 2 ( 7 ) , and C(6)< (7) The contribution of the resonance structures (c) to the overall structures of 4 and 9 could also explain the results of the variable temperature 'H nmr spectra of 9 which show a lower barrier to rotation about the amide C-N bond than observed for other boron-chelated N,N-dialkylamide functions (7)(8)(9)(10)(11)(12). A similar lowering of the rotational barrier about the amide C-N bond has been reported for both N,N-dimethyl- (24) and N,Ndiethylsalicylamide (25).…”

“…There are some examples in the literature of boron chelates with N,N-dialkylarnide groups displaying two different N-alkyl signals in their 'H nrnr spectra. This has been associated with the barrier to rotation about the amide C-N bond and therefore complexation through the amide oxygen atom (7)(8)(9)(10). The signal separation appears at room temperature and has even been observed at temperatures ranging from 50 to 120°C (9).…”