The addition of CH3CHO to a chloroform solution of H(μ-H)Os3(CO)10(NH3) affords the new H(μ-H)Os3(CO)10(HNCHCH3) derivative where the imine ligand occupies a terminal position. The stereochemistry of the adduct appears to be determined by the occurrence of an unconventional hydrogen-bond interaction involving the N−H moiety and the terminal hydride.

Unconventional hydrogen-bond interactions involving metal hydrides as proton acceptors from N−H bonds have been recently discovered in mononuclear organometallic systems. The work herein reported on H2Os3(CO)10L (L= NH2Et, NHEt2) suggests that this type of interaction may be even more important in cluster chemistry in directing the stereochemistry of the products as well as affecting the intramolecular ligand exchange processes.

The new water-soluble amphiphilic phosphines R-(C 6 H 4 )-(OCH 2 CH 2 ) n P(Ph)CH 2 CH 2 SO 3 -Na (R ) tert-octyl, n j ) 1.4, 5.1, 11.2; R ) n-nonyl, n j ) 1.6, 5.6, 11.4) and RP(Ph)CH 2 CH 2 SO 3 Na (R ) n-octyl, CH 3 (OCH 2 CH 2 ) 3 ) have been synthesized and characterized by NMR ( 1 H, 13 C, 31 P) and ES mass spectroscopy. The respective Pd(II) complexes were prepared by reaction with PdCl 2 (COD). Water solutions of ligands and Pd(II) complexes exhibit surfactant properties that have been studied by surface tension measurements. The critical micelle concentration (cmc) and the area occupied per molecule absorbed in the air/water interface were determined. These data show that the cmc's of ligands are significantly higher than those of their respective metal complexes. This finding can be understood by considering the metal complex as a pseudo gemini surfactant. The values of area occupied per molecule in the interface show that ligands with a middle polyether chain yielded the metal complexes with the highest metal concentration in the interface.

The presence of an intramolecular XH···HM interaction between the imine proton donor and the terminal hydride in H(μ-H)Os3(CO)10(HNCPh2) has been investigated by X-ray analysis, NMR and IR spectroscopy and theoretical calculations. The localization of the hydrogen atoms in the crystal structure yielded a H···H distance of 1.79(6) Å for this “unconventional” H···H interaction; theoretical calculations suggested an H···H distance of 1.89 Å in the solid state. A NMR determination of the interproton distance, obtained from the isolation of the selective H,H dipolar contribution to the hydride relaxation time, afforded a value of 2.00 ± 0.05 Å. The difference between NMR and solid state determinations may be explained on the basis of the occurrence, in solution, of a large amplitude oscillatory motion of the imine ligand along the N−Os coordination axis. Further evidence of the presence of the favorable N−H···H−M intramolecular hydrogen bond interaction has been obtained from the red shift of the ν(N−H) stretching in H(μ-H)Os3(CO)10(HNCPh2) with respect to that of the related Os3(CO)11(HNCPh2) compound. DFT(B3LYP) calculations gave results in agreement with the experimental findings and allowed further insight into the nature of the N−H···H−M dihydrogen bond, pinpointing the electrostatic nature of this interaction and the role of the high polarizability of the Os−H bond.