- Aryl Insertion vs Aryl-Aryl Coupling in C,C-Chelated Organoborates: The "missing Link" of Tetraarylborate Photochemistry
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The photoreactivity of 9-borafluorene-based, C,C-chelated organoborates was investigated. Unlike the related tetraarylborates, the charge-transfer transitions imparted by the biphenyl chelate lead to selective insertion of one aryl substituent into the endocyclic B-C bond of the 9-borafluorene moiety, resulting in the formation of boratanorcaradienes. This photoreaction likely proceeds according to a Zimmerman rearrangement, which is analogous to one of the initially proposed mechanisms for tetraarylborates and provides additional insight into these long-debated photochemical reactions.
- Radtke, Julian,Mellerup, Soren K.,Bolte, Michael,Lerner, Hans-Wolfram,Wang, Suning,Wagner, Matthias
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- Bis(phosphino)borates: A new family of monoanionic chelating phosphine ligands
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The reaction of dimethyldiaryltin reagents Me2SnR2 (R = Ph (1), p-MePh (2), m,m-Me2Ph (3), p-tBuPh (4), p-MeOPh (5), p-CF3Ph (6)) with BCl3 provided a high-yielding, simple preparative route to the corresponding diarylchloroboranes R2BCl (R = Ph (10), p-MePh (11), m,m-Me2Ph (12), p-tBuPh (13), p-MeOPh (14), p-CF3Ph (15)). In some cases, the desired diarylchloroborane was not formed from an appropriate tin reagent Me 2SnR2 (R = o-MeOPh (7), o,o-(MeO)2Ph (8), o-CF3Ph (9)). The reaction of lithiated methyldiaryl- or methyldialkylphosphines with diarylchloroboranes or dialkylchloroboranes is discussed. Specifically, several new monoanionic bis(phosphino)borates are detailed: [Ph2B(CH2PPh2)2] (25); [(p-MePh)2B(CH2PPh2)2] (26); [(p-tBuPh)2B(CH2PPh2)2] (27); [(p-MeOPh)2B-(CH2PPh2)2] (28) ; [(p-CF3Ph)2B(CH2PPh2) 2] (29); [Cy2B(CH2PPh2) 2] (30); [Ph2B(CH2P{p-tBuPh} 2)2] (31);[(p-MeOPh)2B-(CH2P{p- tBuPh}2)2] (32); [Ph2B(CH 2P{p-CF3Ph}2)2] (33); [Ph 2B(CH2P(BH3)(Me)2)2] (34); [Ph2B(CH2P(S)(Me)2)2] (35); [Ph2B(CH2P1Pr2)2] (36); [Ph2B(CH2PtBu2)2] (37); [(m,m-Me2Ph)2B(CH2PtBu 2)2] (38). The chelation of diarylphosphine derivatives 25-33 and 36 to platinum was examined by generation of a series of platinum dimethyl complexes. The electronic effects of substituted bis(phosphino)borates on the carbonyl stretching frequency of neutral platinum alkyl carbonyl complexes were studied by infrared spectroscopy. Substituents remote from the metal center (i.e. on boron) have minimal effect on the electronic nature of the metal center, whereas substitution close to the metal center (on phosphorus) has a greater effect on the electronic nature of the metal center.
- Thomas, J. Christopher,Peters, Jonas C.
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p. 5055 - 5073
(2008/10/08)
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