Addition of Nitrogen-Containing Heteroallenes to Iron(II)-Hydrides

Abstract

The reactions between cis-Fe(dmpe) 2 H 2 (dmpe ) Me 2 PCH 2 CH 2 PMe 2 ) (1) or cis-Fe(PP 3 )H 2 (PP 3 ) P(CH 2 CH 2 PMe 2 ) 3 ) (2) and phenyl isothiocyanate (PhNCS), ethyl isothiocyanate (EtNCS), and phenyl isocyanate (PhNCO) were investigated. PhNCS reacts with 1 to form a variety of insertion products at low temperature, and the thermodynamic product hydridoiron N-phenylthioformimidate trans-Fe(dmpe) 2 (SCHNPh)H (3a) at 300 K. Addition of an excess of PhNCS to 1 produces the bis(insertion) product trans-Fe(dmpe) 2 (SCHNPh) 2 (3c). EtNCS inserts into the iron-hydride bond of 1 to form a mixture of trans-Fe(dmpe) 2 -(SCHNEt)H (4a, thermodynamic product) and cis-Fe(dmpe) 2 (SCHNEt)H (4b, kinetic product). Addition of an excess of EtNCS does not result in a second insertion but rather attack at the thioformimidato ligand to form trans-Fe(dmpe) 2 (SCHN + (Et)C(S)N -Et)H (4c). PhNCO reacts rapidly with 1 to form trans-Fe(dmpe) 2 (OCHNPh)H (5a) and higher oligomeric products. The addition of PhNCS, EtNCS, and PhNCO to 2 permits the formation of thermally stable, geometrically constrained cis products cis-Fe(PP 3 )(SCHNPh)H (6a), cis-Fe(PP 3 )(SCHNEt)H (7a), and cis-Fe(PP 3 )(OCHNPh)H (8a) in clean reactions. The hydridoiron N-phenylthioformimidate 6a reacts with a second equivalent of PhNCS to form cis-Fe(PP 3 )-(SCHNPh) 2 (6c), but oligomerization of EtNCS or PhNCO does not occur. All complexes have been characterized by multinuclear NMR andIR spectroscopy and mass spectrometry (electrospray), with elemental analysis or high resolution mass spectrometry confirming the structures of thermally stable complexes where possible. Complexes 3c and 4c were characterized by single-crystal X-ray crystallography.

Reactivity of ortho‐Substituted Aryl–Palladium Complexes towards Carbodiimides, Isothiocyanates, Nitriles, and Cyanamides

“…Isothiocyanates insert into MÀO (M= Re, [44,45] Ni, [46] Cu, [47] Zn [48] ), MÀN (M= Mg, [34] Yb, [39] Ln, [38,49] Re, [50] Fe, [51] Ni, [46] Pd, [52] ), MÀH (M= Zr, [53] Nb, Ta, [54] Ru, Os, Ir, [55] Rh [56] ), M À S (M= Nd [57] ), and M À C (M= Mg, [34,58] Al, [59] Zr, [60] Nb, Ta, [61] Re, [62] Fe, [63] Co, [64] Ni, [65] Pd [10] ) bonds in the same way as carbodiimides. We have recently reported the first example of insertion of an isothiocyanate into a Pd À C bond followed by formation of PdS.…”

A quantitative measure of the ionicity of selected iron hydride species by examination of the deuterium quadrupole coupling constant (DQCC)

“…While the distribution of ionicity values was fairly nar- row, the trends in T 1min and DQCC values are informative. The most ionic iron hydride examined was cis-Fe(dmpe) 2 (SC(@NMe)D)D (4-d 2 ), although insertion into its Fe-D/H bond has not yet been observed [26]. On the other hand, trans-Fe(dmpe) 2 (SC(@NMe)D)D (5-d 2 ), less ionic than its isomer 4-d 2 , cis-Fe(dmpe) 2 (SC(@NMe)D)D, was sufficiently nucleophilic to undergo reaction with a second equiv of Me-N@C@S to give 6-d 2 , trans-Fe(dmpe) 2 (SC(@N + (Me)C(@S)N À Me)D)D. The less ionic complexes, cis-Fe(dmpe) 2 D 2 (1-d 2 ), cis-Fe(PP 3 )D 2 (2-d 2 ) and trans-Fe(dmpe) 2 (OC@OD)D (3-d 2 ) are the only species within the series to undergo clean insertion reactions; the tolyl-derivative, 7, gave several such insertion products.…”

Iron Dihydride Complexes: Synthesis, Reactivity, and Catalytic Applications

“…The reaction of (P C2 P Me 3 )FeH 2 with CS 2 gave intractable products, but with a careful control of the amount and the temperature, the mono‐insertion product (P C2 P Me 3 )FeH(SCSH) could be formed quantitatively. EtNCS and PhNCO were shown to insert once regardless of the amount used . In contrast, the mono‐insertion product generated from PhNCS reacted with the isothiocyanate further to yield two complexes with one of them being assigned as a double‐insertion product.…”

“…Isothiocyanates and isocyanates could insert either the C=S/C=O or the C=N bond into a transition metal hydride. Phenyl isothiocyanate (PhNCS) started to react with cis ‐(dmpe) 2 FeH 2 when the temperature was raised above −13 °C, resulting in five different products . The reaction performed at 27 °C generated the thermodynamic product trans ‐(dmpe) 2 FeH(SCHNPh), or trans ‐(dmpe) 2 Fe(SCHNPh) 2 when more PhNCS was added (Figure ).…”

“…The reaction performed at 27 °C generated the thermodynamic product trans ‐(dmpe) 2 FeH(SCHNPh), or trans ‐(dmpe) 2 Fe(SCHNPh) 2 when more PhNCS was added (Figure ). The 1 : 1 reaction between alkyl isothiocyanate RNCS (R=Me, Et) and cis ‐(dmpe) 2 FeH 2 gave cis ‐(dmpe) 2 FeH(SCHNR) as the kinetic product, which gradually isomerized to the more stable trans isomer ,. Interestingly, adding the second equivalent of RNCS did not form the expected bis‐insertion product, but instead produced an iron hydride complex ligated by the dimerized isothiocyanate.…”