The aprotic and protic bi- and multidentate iminophosphines 2-Ph
2PC
6H
4N=CR
1R
2 (R
1=H, R
2=Ph=
2a; R
1=Me R
2=Ph=
2b; R
1=H, R
2=2-thienyl=
2c; R
1=H, R
2=C
6H
4-2-PPh
2=
2d; R
1=H, R
2=C
6H
4-2-OH=
2e, R
1=H, R
2=C
6H
4-2-OH-3-Bu
t=
2f; R
1=H, R
2=CH
2C(O)Me=
2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine
2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph
2PC
6H
4N(H)CH
2C
6H
4-2-PPh
2 (
2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1
H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give
N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(
o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph
2PC
6H
4N=C(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph
2PC
6H
4N=C(H)Ph}ClX] and the imino-diphosphine 2-Ph
2PC
6H
4N=C(H)C
6H
4-PPh
2 reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph
2PC
6H
4N=C(H)C
6H
4---PPh
2}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph
2PC
6H
4N=C(Me)CH
2C(O)Me reacts with [Ni(PPh
3)
2Cl
2] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph
2PC
6H
4N=C(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines
2a–
h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd
2(OAc)
6] giving consistently higher conversions than those formed from [Pd
2(dba)
3] and [PdCl
2(MeCN)
2]. Catalysts formed from neutral bi- and terdentate iminophosphines
2a–
d gave significantly higher conversions than those formed from their monobasic counterparts
2e–
f. Notably, under our conditions the conversions obtained with
2a–
c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-
tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]
2 and
2a–
h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines
2e–
f giving the highest conversions.
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