Addition of nitrogen-containing heteroallenes to iron(II)-hydrides

The reactions between cis-Fe(dmpe)(2)H-2 (dmpe = Me2PCH2CH2PMe2) (1) or cis -Fe(PP3)H-2 (PP3 = P(CH2CH2PMe2)(3)) (2) and phenyl isothiocyanate (PhNCS), ethyl isothiocyanate (EtNCS), and phenyl isocyanate (PhNCO) were investiga ted. PhNCS reacts with 1 to form a variety of insertion products at low tem perature, and the thermodynamic product hydridoiron N-phenylthioformimidate trans-Fe(dmpe)(2)(SCHNPh)H (3a) at 300 K. Addition of an excess of PhNCS t o 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 t rans-Fe(dmpe)(2)(SCHN+(Et)C(S)N-Et)H (4c). PhNCO reacts rapidly with 1 to f orm trans-Fe(dmpe)(2)(OCHNPh)H (5a) and higher oligomeric products. The add ition of PhNCS, EtNCS, and PhNCO to 2 permits the formation of thermally st able, geometrically constrained cis products cis-Fe(PP3)(SCHNPh)H (6a), cis Fe(PP3)(SCHNEt)H (7a), and cis-Fe(PP3)(OCHNPh)H (8a) in clean reactions. Th e hydridoiron N-phenylthioformimidate 6a reacts with a second equivalent of PhNCS to form cis-Fe(PP3)(SCHNPh)(2) (6c), but oligomerization of EtNCS or PhNCO does not occur. All complexes have been characterized by multinuclea r NMR andIR spectroscopy and mass spectrometry (electrospray), with element al analysis or high resolution mass spectrometry confirming the structures of thermally stable complexes where possible. Complexes 3c and 4c were char acterized by single-crystal X-ray crystallography.