Rhodium(I) complexes of α-keto-stabilised 1,2-bis(diphenylphosphino)alkane mono ylides
Rhodium(I) complexes of the hybrid ylide-phosphine ligands, Ph2P(CH2)nPPh2(CHC(O)C6H5) (n = 1: dppm-yl, or 2: dppe-yl) have been synthesised from [Rh(μ-C1)(COD)]2 (COD = 1,5-cyclooctadiene) and characterized by NMR spectroscopic and X-ray structural methods. The dppe-yl behaves as an ambidentate ligand; it functions as a monodentate P-donor ligand with a dangling ylidic carbon in the neutral chloro complex, [(COD)Rh(Cl)(dppe-yl)] (1), whereas replacement of the chloride by a non-coordinating counter anion results in the formation of the complexes, [(COD)Rh(L-L’)]+ (L-L’ = dppe-yl (2) or dppm-yl (3)) respectively in which the ligands are bonded to the metal via the phosphorus and the ylidic carbon atoms. The 1,5-cyclooctadiene (COD), present in the Rh(I) precursor, remains intact in the products. The structures of1,2 and3 have been confirmed by X-ray crystallography.
Synthesis, structure, and reactivity of ylide rhodium(I) and rhodium (III) complexes
Abstract The olefin(ylide) rhodium(I) complexes [(L)( i Pr 3 PCH 2 )Rh(Cl] 2 ( 3 : L = C 8 H 14 ; 4 : L = C 2 H 4 ) have been prepared from [(L) 2 RhCl] 2 ( 1 , 2 ) and CH 2 P i Pr 3 in almost quantitative yield. Upon treatment of 3 and 4 with LiC 5 H 5 , the half-sandwich type compounds [C 5 H 5 Rh(CH 2 P i Pr 3 )(L)] ( 5, 6 ) are obtained. Compound 5 (L = C 8 H 14 ) reacts with carbon monoxide to give [C 5 H 5 Rh(CH 2 P i Pr 3 )(CO)] ( 7 ) and with iodine to give [C 5 H 5 Rh(CH 2 P i Pr 3 )I 2 ] ( 8 ). Displacement of the olefin ligand also occurs upon treatment of 5 with CH 3 I, CH 2 I 2 and CH 2 ClI, leading to the formation of [C 5 H 5 RhCH 2 X(CH 2 P i Pr 3 )I] 9 : X = H; 10 : X = I; 11 : X = Cl). The bis(ylide) rhodium(III) complexes [C 5 H 5 Rh(CH 2 PR 3 )(CH 2 P i Pr 3 )I]I ( 12 – 14 ), [C 5 H 5 Rh(CH 2 P i Pr 3 )(CH 2 AsPh 3 )I]I ( 5 ) and [C 5 H 5 Rh(CH 2 P i Pr 3 )(CH 2 NEt 3 )I]I ( 16 ) are obtained by nucleophilic substitution from 10 upon treatment with Pr 3 , AsPh 3 and NEt 3 , respectively. Reaction of 7 with CH 3 I or CD 3 I give a mixture of 8 and [C 5 H 5 RhCX 3 (CH 2 P i Pr 3 )(CO)I ( 17a : X = H; 17b : X = D). I contrast, treatment of 7 with dimethylsulfate gives only [C 5 H 5 RhCH 3 (CH 2 P i Pr 3 )-(CO)]SO 4 Me ( 17c ). The X-ray crystal structure of 17c has been determined. Compound 17c reacts with P i Pr 3 to give the acetyl(ylide) rhodium(III) complex [C 5 H 5 RhCOCH 3 (CH 2 P i Pr 3 (P i Pr 3 )]SO 4 Me ( 18 ).
Dating of Historical Manuscripts Using Spectrometric Methods: A Mini-Review
An overview is provided of spectrometric methods useful for age estimation of historical manuscripts (medieval ones in particular), in order to confirm their authenticity. Individual methods (infrared and Raman spectroscopy, mass spectrometry, atomic emission spectroscopy, X-ray spectroscopy, and electron scanning microscopy) are discussed and examples of their application described. The following general strategy can be recommended for dating and/or authenticating of historical manuscripts. First of all, the pigment analysis should be carried out using Raman spectroscopy (distinguishing the period and modern pigments), followed by PIXE ink analysis (solving the question of ink homogeneity). Finally, the radiocarbon dating of the writing support, potentially supplemented by the ink dating using scanning Auger microscopy should be performed.