Synthesis and insertion behavior of carbonylhydridonitrosyltris(trimethylphosphine)tungsten(0)

Two routes for the synthesis of mer-W(CO)(H)(NO)(PMe3)(3) (4) are described , starting from mer-W(Cl)(CO)(NO)(PMe3)(3) (1) or the borohydride complex m er-W(eta (1)-BH4)(CO)(NO)(PMe3)(3) (3). The propensity of 4 to undergo inse rtion reactions has been investigated. 4 reacts with benzaldehyde, propiona ldehyde, pivalaldehyde, benzophenone, acetophenone, and acetone to afford t he corresponding alkoxide complexes mer-W(CO)(NO)(PMe3)(3)(OCHR 'R ") (R ' = H, R " = Ph (5a); R ' = H, R " = CH2CH2CH3 (5b); R ' = H, R " = CH2C(CH3) 3 (5C); RI = Ph, R " = Ph (5d); R ' = CH3, R " = Ph (5e); R ' = CH3, R " = CH3 (5f)). Insertion of CO2 yields the formato-O complex mer-W(CO)(NO)(OCHO )(PMe3)(3) (6). Reaction of 4 with CO leads to immediate loss of PMe3 and f ormation of trans, trans-W(CO)(2)(H)(NO)(PMe3)(2). In a reversible way Fe(C O)(5) and Re-2(CO)(10) insert into the W-H bond of 4, affording the isolabl e mu -formyl complex mer-W(CO)(NO)(PMe3)(3)[(mu -OCH)Fe(CO)(4)] (7a) and me r-W(CO)(NO)(PMe3)B [(mu -OCH)Re-2(COM (7b) as an equilibrium constituent. F or both reactions equilibrium constants have been derived from VT-NMR measu rements and DeltaH values were calculated (-46 kJ/mol for 7a and -26 kJmmol for 7b). An accompanying DFT analysis of the W-H bond demonstrated that a higher number of phosphine ligands in a W(CO)(4-n)(H)(NO)(PMe3)(n) series i ncreases the hydridic character of the Il ligand and induces a stronger bon d polarization. The relative DeltaH values for the insertions of the metal carbonyls with n = 3 could be reproduced. The calculations also suggest tha t the main difference in the reactivity of Fe(CO)(5) and Re-2(CO)(10) is no t primarily an electronic effect but, rather, is due to steric influence. C ompounds 3, 4, 6, and 7a were structurally characterized by X-ray diffracti on studies.