Silicon-phosphorus multiple bonds

The investigated transients with double bonds to silicon exhibit short effective 1/e lifetimes ranging from a few ms (for H2Si=0) up to ca. 30 ms for 3a. In contrast to these silanes, the kinetic instability of multiply-bonded transient phosphines depends more strongly on the electronegativity of the element involved in the multiple bond to phosphorus. The observed 1/e lifetimes span a substantial range from 8 ms for highly reactive 14a up to stable derivatives with unprotected phosphorus-carbon multiple bonds. FVT coupled with FTIR spectroscopy has proved to be a competitive technique to study robustly bound transients with 1/e lifetimes as short as 8 ms. 

Driess, Matthias, Silicon-Phosphorus and Silicon-Arsenic Multiple Bonds. 39 193... 

Silicon-Phosphorus and Silicon-Arsenic Multiple Bonds... 

Classical shielding arguments indicate an electron-rich phosphorus atom, or equally, an increase in coordination number. The silicon atom seems also to be electron-rich, while the carbon has a chemical shift in the range expected for a multiply bonded species. The coupling constant data are difficult to rationalize, as it is not possible to predict the influence of orbital, spin-dipolar, Fermi contact, or higher-order quantum mechanical contributions to the magnitude of the coupling constants. However, classical interpretation of the NMR data indicates that the (phosphino)(silyl)carbenes have a P-C multiple bond character. 

For many years the occurrence of double and triple bonds such as discussed above for silicon and phosphorus was equally rare among other nonmetals, leading to the conclusion that only C=C, C =N, C 0. NsN. etc. were stable multiple bonds. This, of course, was taken as challenge and much svnthetic work was directed at the problem. None of the multiple bonds between heavier nonmetals is as strong as those between the 2p elements. Some typical estimates of the strength of the n bond (cf. to H,C CH3 as a "standard" from organic chemistry) arc (values in kJ mol-1). ... 

Element-element bonds, addition to G-G multiple bonds arsenic—selenium bonds, 10, 782 boron—boron bonds, 10, 727 boron—sulfur bonds, 10, 778 B-S and B-Ge bonds, 10, 758 chalcogen—chalcogen additions, 10, 752 germanium—germanium bonds, 10, 747 germanium-tin bonds, 10, 780 overview, 10, 725-787 phosphorus—phosphorus bonds, 10, 751 phosphorus—selenium bonds, 10, 782 phosphorus-sulfur bonds, 10, 781 Se-Si and Se-Ge bonds, 10, 779 silicon-germanium bonds, 10, 770 silicon-phosphorus bonds, 10, 780 silicon-silicon bonds, 10, 734 silicon-sulfur bonds, 10, 779 silicon-tin bonds, 10, 770 tin-boron bonds, 10, 767 tin-tin bonds, 10, 748... 

Homonuclear carbonyl dimers, palladium complexes, 8, 206 Homonuclear element-element bonds, addition to C-C multiple bonds boron-boron bonds, 10, 727 chalcogen-chalcogen additions, 10, 752 germanium-germanium bonds, 10, 747 phosphorus-phosphorus bonds, 10, 751 silicon—silicon bonds, 10, 734 tin—tin bonds, 10, 748... 

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