Insertion of CO2, CS2, and COS into iron(II)-hydride bonds

The reactions between cis-Fe(dmpe)(2)H-2 (dmpe = Me2PCH2CH2PMe2) (1) or cis -Fe(PP3)H-2 (PP3 = P(CH2CH2PMe2)(3)) (2) and carbon dioxide (CO2), carbon d isulfide (CS2), and carbonyl sulfide (COS) are investigated. At 300 K, addi tions of CO2 (1 atm), CS2 (2 equiv), and COS (I atm) to 1 result in the for mation of a stable transformato hydride, trans-Fe(dmpe)(2)(OCHO)H (3a), a t rans-dithioformato hydride, trans-Fe(dmpe)(2)(SCHS)H (Ja), and a trans-thio formato hydride, trans-Fe(dmpe)(2)(SCHO)H (5a), respectively. When CSI and COS are added to cis-Fe(dmpe)(2)H-2 at 195 K, a cis-dithioformato hydride, 4b, and a cis-thioformato hydride, 5b, respectively, are observed as the in itially formed products, but there is no evidence of the corresponding cis- formato hydride upon addition of CO2 to cis-Fe(dmpe)(2)H-2 Additions of exc ess CO2, CS2, and COS to 1 at lower temperatures (195-240 K) result in the formation of a trans-bis(formate), trans-Fe(dmpe)(2)(OCHO)(2) (3b), a trans -bis(dithioformate), trans-Fe(dmpe)(2)(SCHS)(2) ( 4c), and a cis-bis(thiofo rmate), cis-Fe(dmpe)(2)(SCHO)(2) (5c), respectively. trans-Fe(dmpe)(2)(SCHO )(2) (5d) is prepared by the addition of excess COS at 300 K. Additions of CO2 (1 atm). CS2 (0.75 equiv), and COS (I atm) to 2 at 300 K result in the formation of a thermally stable, geometrically constrained cis-formato hydr ide, cis-Fe(PP3)(OCHO)H (6a), a cis-dithioformato hydride, cis-Fe(PP3)(SCHS )H (7a), and a cis-thioformato hydride, cis-Fe(PP3)(SCHO)H (8a), respective ly. Additions of excess CO2 and COS to 2 yield a cis-bis(formate), cis-Fe(P P3(OCHO)(2) (6b), and a thermally stable cis-bis(thioformate), cis-Fe(PP3)( SCHO)(2) (8b), respectively. All complexes an characterized by multinuclear NMR spectroscopy, with IR spectroscopy and elemental analyses confirming s tructures of thermally stable complexes where possible. Complexes 3b and 5a are also characterized by X-ray crystallography.