P2S2-Bridged binuclear metal carbonyls from dimerization of coordinated thiophosphoryl groups: a theoretical study

Theoretical studies indicate the complexes M(CO)_n(PS) with bent 1-e/2-e donor PS groups to be unstable for giving the stable M(CO)_n−1(PS) with linear 3-e donor PS groups. In addition, only Mn₂(CO)₈(P₂S₂) is energetically viable from the Mn(CO)₄(PS).

Structural Trends in Monoboronyl Compounds: Analysis of the Interaction of Second-Row Elements with BO

A theoretical study of the monoboronyl compounds of second-row elements, [XBO] (X = Na, Si, P, S, Cl), has been carried out. It is observed that the preference for the XBO arrangement is higher when moving to the right of the period. In the case of sodium monoboronyl three minima were characterized, all lying rather close in energy: linear NaBO, linear NaOB, and an L-shaped structure. Linear NaBO and the L-shaped structure are nearly isoenergetic, whereas linear NaOB is located 2.11 kcal/mol above linear NaBO. The barrier for the conversion of the L-shaped structure into linear NaBO is about 5.1 kcal/mol, suggesting that both species could be potential targets for experimental detection. For silicon monoboronyl, two minima, linear SiBO and linear SiOB, are found, the latter lying about 13 kcal/mol above SiBO. The barrier for the isomerization of SiOB into SiBO is estimated to be 11.4 kcal/mol. For phosphorus, sulfur, and chlorine monoboronyls the linear XBO isomer is clearly the most stable one, and the barriers for the conversion into XOB species are relatively high, suggesting that quite likely the linear XBO isomer should be the main experimental target. All studied monoboronyls are relatively stable, with dissociation energies increasing from left to right of the second-row (69.8 kcal/mol for NaBO and 118.98 kcal/mol for ClBO). An analysis of the bonding for second-row monoboronyls has been carried out, emphasizing the different characteristics of the X-B and X-O bonds along the second row.

Donor-Stabilized 1,3-Disila-2,4-diazacyclobutadiene with a Nonbonded Si⋅⋅⋅Si Distance Compressed to a Si=Si Double Bond Length

A donor-stabilized 1,3-disila-2,4-diazacyclobutadiene presents an exceptionally short nonbonded Si⋅⋅⋅Si distance (2.23 Å), which is as short as that of Si=Si bonds (2.15-2.23 Å). Theoretical investigations indicate that there is no bond between the two silicon atoms, and that the unusual geometry can be related to a significant coulomb repulsion between the two ring nitrogen atoms. This chemical pressure phenomenon could provide an alternative and superior way of squeezing out van der Waals space in highly strained structures, as compared to the classical physical methods.