61726-36-1Relevant articles and documents
Bis(phosphino)borates: A new family of monoanionic chelating phosphine ligands
Thomas, J. Christopher,Peters, Jonas C.
, p. 5055 - 5073 (2008/10/08)
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.
Reduction of Halosilanes by Organotin Hydrides
Wilt, James W.,Belmonte, Frank G.,Zieske, Paul A.
, p. 5665 - 5675 (2007/10/02)
A study of the reduction of halosilanes with organotin hydrides is described.The free radical chain mechanism indicated by the results obtained parallels that known for the comparable reduction of haloalkanes, but the reactivity of α-haloalkanes is considerable enhanced.Mechanistic studies suggest that the polar nature of the halogen abstraction step in the radical chain sequence, which places incremental negative charge adjacent to silicon, is the principal reason for this enhanced reactivity.Structure-reactivity studies indicat the gem-dimethylsilyl function to be an electronic transmitter.The ρ values for reduction of aryldimethyl(chloromethyl)silanes and substituted benzyl chlorides by tri-n-butyltin hydride are essentially identical (+0.45).Reduction of (chloromethyl)trimethylsiulane with aryldimethyltin hydrides, conversely, yielded a ρ value of -1.61.The reduction produced racemic product from an optically active α-chlorosilane, the synthesis of which appears to the first reported.Other syntheses of variuos halosilanes of interest are also described.The title reduction is specific for carbon-halogen bonds.Silicon-halogen bonds are not affected, a distinction that should make the reduction synthetically useful.Because the increased reactivity of α-halosilanes in the reduction has thus been ascribed to a kinetic polar effect in a critical step of the mechanism, no compelling argument for special thermodynamic stability in α-silyl radicals themselves can be made.
