Manganese germylene complexes: reactivity with dihydrogen, isonitriles, and dinitrogen.

The manganese germylene-hydride complexes [(dmpe)MnH(GeR)] (1a: R = Ph, 1b: R = Et) reacted with H (approx. 1.5 atm) to afford the 'germyl dihdyride' species [(dmpe)MnH(GeHR)] (2a: R = Ph, 2b: R = Et) as an equilibrium mixture with the starting material (1a-b). In solution, 2a-b exist as a mixture of isomers where the major isomer (71-84%) is a hydrogermane hydride complex -[(dmpe)MnH(HGeHR)] (transHGe-2a-b). The minor isomer of 2a-b is tentatively assigned as the germyl dihydrogen complex -[(dmpe)Mn(GeHR)(H)] (cis-2a-b), possibly in rapid equilibrium with a small amount of the germanate complex [(dmpe)Mn(HGeHR)] (central-2a-b). DFT calculations were employed to gain insight into the nature of bonding in the isomers of 2a-b, and an X-ray crystal structure was obtained for -[(dmpe)MnH(HGeHEt)] (transHGe-2b) which co-crystallized with 1b. Reactions of 1a-b with D suggest a pathway that proceeds conversion of 1a-b to a 5-coordinate germyl intermediate [(dmpe)Mn(GeHR)] (A) prior to reaction with H/D. Providing support for this pathway, intermediate A (R = Ph) was trapped reactions of 1a with isonitriles, affording the manganese(I) germyl isonitrile complexes [(dmpe)Mn(GeHPh)(CNR)] (3a: R = Bu, 3b: R = -xylyl, and 3c: R = Bu). These complexes formed as a mixture of and isomers, and X-ray quality crystals were obtained for cis-3a, cis-3b and trans-3c. Complexes 1a-b also reacted slowly with dinitrogen at room temperature to afford germyl dinitrogen complexes [(dmpe)Mn(GeHR)(N)] (5a: R = Ph, 5b: R = Et). Compounds 5a-b were initially formed as isomers, but the isomer is the thermodynamic product in each case, and the and isomers were crystallographically characterized for both 5a and 5b. X-ray crystallography, IR spectroscopy, and DFT calculations were employed to compare metal-dinitrogen bonding in the and isomers of 5a-b. The silyl dinitrogen derivative [(dmpe)Mn(SiHPh)(N)] (6) was also generated as a mixture of the and isomers, and the isomer was structurally characterized. The isomers of 5b and 6 show Mn-P coupling in the P{H} and Mn{H} NMR spectra, affording 1 : 1 : 1 : 1 : 1 : 1 sextets and 1 : 4 : 6 : 4 : 1 quintets, respectively.