title: Borylene-based direct functionalization of organic substrates: synthesis, characterization, and photophysical properties of novel pi-conjugated borirenes.
abstract: Room temperature photolysis of aminoborylene complexes, [(CO)(5)M=B=N(SiMe(3))(2)] (1: M = Cr, 2: Mo) in the presence of a series of alkynes and diynes, 1,2-bis(4-methoxyphenyl)ethyne, 1,2-bis(4-(trifluoromethyl)phenyl)ethyne, 1,4-diphenylbuta-1,3-diyne, 1,4-bis(4-methoxyphenyl)buta-1,3-diyne, 1,4-bis(trimethylsilylethynyl)benzene and 2,5-bis(4-N,N-dimethylaminophenylethynyl)thiophene led to the isolation of novel mono and bis-bis-(trimethylsilyl)aminoborirenes in high yields, that is [(RC=CR)(mu-BN(SiMe(3))(2)], (3: R = C(6)H(4)-4-OMe and 4: R = C(6)H(4)-4-CF(3)); [{(mu-BN(SiMe(3))(2)(RC=C-)}(2)], (5: R = C(6)H(5) and 6: R = C(6)H(4)-4-OMe); [1,4-bis-{(mu-BN(SiMe(3))(2)(SiMe(3)C=C)}benzene], 7 and [2,5-bis-{(mu-BN(SiMe(3))(2) ((C(6)H(4)NMe(2))C=C)}-thiophene], 8. All borirenes were isolated as light yellow, air and moisture sensitive solids. The new borirenes have been characterized in solution by (1)H, (11)B, (13)C NMR spectroscopy and elemental analysis and the structural types were unequivocally established by crystallographic analysis of compounds 6 and 7. DFT calculations were performed to evaluate the extent of pi-conjugation between the electrons of the carbon backbone and the empty p(z) orbital of the boron atom, and TD-DFT calculations were carried out to examine the nature of the electronic transitions.
authors.affiliation: Institut für Anorganische Chemie, Bayerische Julius-Maximilians-Universität Würzburg Am Hubland, 97 074 Würzburg, Germany. H.Braunschweig@mail.uni-wuerzburg.de
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.forename: Thomas
authors.initials: T
authors.lastname: Herbst
authors.forename: Daniela
authors.initials: D
authors.lastname: Rais
authors.forename: Sundargopal
authors.initials: S
authors.lastname: Ghosh
authors.forename: Thomas
authors.initials: T
authors.lastname: Kupfer
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Radacki
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Crawford
authors.forename: Richard M
authors.initials: RM
authors.lastname: Ward
authors.forename: Todd B
authors.initials: TB
authors.lastname: Marder
authors.forename: Israel
authors.initials: I
authors.lastname: Fernández
authors.forename: Gernot
authors.initials: G
authors.lastname: Frenking