Synthesis, Molecular Structure, and Reactivity of Rhodium(I) Complexes with Diazoalkanes and Related Substrates as Ligands

Abstract

A series of (diazoalkane)rhodium(I) compounds of the general composition trans-[RhCl(N2CRR‘)(PiPr3)2] with R = R‘ = Ph, p-C6H4Me, p-C6H4Cl and R = Ph, R‘ = p-C6H4Me, o-C6H4Me, CH3, CH2Ph, CF3 has been prepared from the dimer [RhCl(PiPr3)2]2 (1) and the diazoalkane. This preparative route has also been extended to complexes in which the N2C unit(s) of 1,4-C6H4{C(Ph)N2}2, 9-diazofluorene, 9,10-anthraquinone-9-diazide, and 3-methyl-1,4-naphthoquinone-1-diazide is (are) linked to a 14-electron [RhCl(PiPr3)2] fragment. While C(CO2Et)2N2 behaves as expected and affords upon treatment with 1 the complex trans-[RhCl{N2C(CO2Et)2}(PiPr3)2), CH(CO2Et)N2 reacts with the same starting material to give the dinitrogen derivative trans-[RhCl(N2)(PiPr3)2] (12). The reactions of trans-[RhCl(C2H4)(PiPr3)2] (2) with both N2CC4Cl4 and N2CC4Ph4 afford trans-[RhCl(N2CC4X4)(PiPr3)2] (X = Cl, Ph), and the same type of ligand exchange takes place by treatment of trans-[RhCl(C2H4)(SbiPr3)2] with N2CC4Cl4. The reactions of trans-[RhCl(N2CRR‘)(PiPr3)2] (3−7, where R and R‘ are aryl) with excess ethene give, instead of a disubstituted cyclopropane, exclusively the trisubstituted olefin CH3CHCRR‘. The reaction of 1 with PhC(R)NNH2 (R = Ph, Me) proceeds mainly by orthometalation to yield the six-coordinate rhodium(III) complexes [Rh(H)Cl{κ2-C,N-C6H4C(NNH2)R}(PiPr3)2]; of these, that with R = Ph reacts with Al2O3 to give trans-[RhCl(N2CPh2)(PiPr3)2] and 12. The alkynylrhodium(I) derivatives trans-[Rh(C⋮CX)(C2H4)(PiPr3)2] (X = H, tBu) behave similarly to 2 and afford upon treatment with Ph2CN2 and C12H8CN2 the corresponding diazoalkane compounds trans-[Rh(C⋮CX)(N2CRR‘)(PiPr3)2] by ligand exchange. The reaction of 2 with the diazo ketones RC(O)C(Ph)N2 (R = Ph, Me) leads to complexes of the general composition [RhCl{N2C(Ph)C(O)Ph}(PiPr3)2], in which the diazo ketone is probably coordinated in a chelating fashion to the metal center. The keto ester derivative (CH3)2CHCH2CH2C(O)C(CO2Me)N2 reacts with 2 to give a mixture of two isomers, one of which could be separated by fractional crystallization. The supposed chelating bonding mode of the diazo ligand in this compound via the terminal nitrogen and the keto oxygen could be confirmed by an X-ray crystal structure analysis.

Formation of Osmium Alkylidene, Alkylidyne, and Dinitrogen Complexes from Reactions of OsCl2(PPh3)3 with Diazoalkanes

“…Complex 10 represents a rare example of a metallacycle derived from diazocabonyl compounds. The only precedents that we are aware of are complexes of the general composition [RhCl­{κ 2 - N,O -N 2 C­(R 1 )­C­(O)­R 2 }­(P i Pr 3 ) 2 ] (R 1 = Ph, R 2 = Me, Ph; R 1 = COOMe, R 2 = (CH 2 ) 2 CH­(CH 3 ) 2 ; R 1 = H, R 2 = CH 2 Ph), which were reported by Werner and his co-workers and produced by reacting trans -[RhCl­(C 2 H 4 )­(P i Pr 3 ) 2 ] with diazo ketones N 2 C­(R 1 )­C­(O)­R 2 . It is noted that it is more common for diazocarbonyl compounds N 2 C­(R)­C­(O)­R′ to form η 1 -( N ) or η 2 -( NN ) complexes. , …”

“…The only precedents that we are aware of are complexes of the general composition Ph), which were reported by Werner and his co-workers and produced by reacting trans-[RhCl(C 2 H 4 )(P i Pr 3 ) 2 ] with diazo ketones N 2 C(R 1 )C(O)R 2 . 32 It is noted that it is more common for diazocarbonyl compounds N 2 C(R)C(O)R′ to form η 1 -(N) or η 2 -(NN) complexes. 33,34 The formation of the η 1 -(C)-diazoalkane intermediate is critical for the generation of a metal alkylidene complex.…”

Reactions of Iron(II) Complexes Supported by Tripodal Amido-Phosphine-Amido Ligands with Diazo Compounds

“…The The solid-state structure of 4, determined by X-ray crystallography, revealed that the diazo ligand is coordinating to the iron center via its terminal nitrogen atom and carbonyl oxygen atom, forming a planar six-membered chelating ring (Figure 6). Thus, complex 4 is among the rare examples of metal complexes featuring chelating diazo-ketone/ester ligands after [RhCl(PPr [15] and [(Bu [29] The distances of Fe1-N3 and Density functional theory (DFT) calculations have been used to further probe the electronic structure of 4. The calculation study at the B3LYP/TZVP/SVP level of theory indicates that the complex has an S＝1 ground spin-state that lies lower in energy than the S＝0 and S＝2 spin states by 70.27 and 57.23 kJ/mol, respectively.…”

“…[6][7][8][9][10] Consequently, there are great interests on the sythesis, structural feature, and reactivity of transition-metal diazoalkane complexes. The known transition-metal diazoalkane complexes are dominated by the complexes of cobalt, nickel, and ruthenium, [11][12][13][14][15][16] whereas the diazoalkane complexes of iron are scarce, which form a sharp contrast to the soaring research interest on iron-catalyzed carbenetransfter reactions. [17] The limited examples of iron diazoalkane complexes include the bis(imino)pyridine complex [(PDI)Fe(η 1 -N 2 CH-SiMe 3 )] (A in Chart 1), [18] the tris(pyrrolido)ethane iron complex [(tpe)Fe(η 1 -N 2 CPh 2 )][Li(THF) 4 ] (tpe＝tris(5-mesitylpyrrolyl)ethane, B), [19] the β-diketiminate iron complex [L Bu-t Fe(η 1 -N 2 CPh 2 )] (L Bu-t ＝ [(DippNCBu t ) 2 CH] -, C) [20] , the cyclopentadienyliron complexes [(η 5 -C 5 H 5 ) Fe(η 1 -N 2 C-Ar 1 Ar 2 )(P-P)]BPh 4 (P-P＝1,2-bis(diphenylphosphine)ethane, 1,3-bis(diphenylphosphine)propane; Ar 1 ＝ Ar 2 ＝ Ph; Ar 1 ＝Ph, Ar 2 ＝p-tolyl; Ar 1 Ar 2 ＝C 12 H 8 , D), [21] as well as the side-on type diazo complexes [(PDI)Fe(η 2 -N,N-N 2 C-Ph 2 )] (E) [22] and [L Bu-t Fe(η 2 -N,N-N 2 CPh 2 )K(OEt 2 )] 2 (F) [20] .…”

Hydridothiazole Rhodium Complexes as a Result of C-H Bond Activation in Iminothiazoles Chelating Ligands

“…Benzylic imines (Ph-CH = NR) are the most studied ligands in the cyclometallation of transition metals [5,6]. It has been reported that intramolecular C-H activation examples of rhodium with Ndonar ligands and C-X (X: halogen) activation with imines [2][3][4][7][8][9]. The first report of ortho-metallation of imines at rhodium via C-H activation has appeared only recently [2][3][4]10].…”