Reactivity of R<sub>2</sub>AlH (R = Me, Bu<sup>i</sup>) and Me<sub>3</sub>M (M = Al, Ga, In) toward the Silylphosphines P(SiMe<sub>3</sub>)<sub>3</sub> and HP(SiMe<sub>3</sub>)<sub>2</sub>

The reactivities of Me<sub>2</sub>AlH with P(SiMe<sub>3</sub>)<sub>3</sub> and of Me<sub>3</sub>M (M = Al, Ga, In) and Bu<sup>i</sup><sub>2</sub>AlH with P(SiMe<sub>3</sub>)<sub>3</sub> and HP(SiMe<sub>3</sub>)<sub>2</sub> were monitored with multinuclear NMR to determine the trend for adduct formation and establish the role that the Me and Bu<sup>i</sup> moieties and M play in influencing the nature of the possible 1,2-elimination product. 1:1 adducts were obtained in the Me<sub>3</sub>M/P(SiMe<sub>3</sub>)<sub>3</sub> systems with no tendency toward room-temperature, 1,2-elimination reactivity. Thermolysis at 100 °C gave the following order of reactivity for SiMe<sub>4</sub> elimination:  Me<sub>3</sub>In·P(SiMe<sub>3</sub>)<sub>3</sub> > Me<sub>3</sub>Ga·P(SiMe<sub>3</sub>)<sub>3</sub> >> Me<sub>3</sub>Al·P(SiMe<sub>3</sub>)<sub>3</sub>. With the Me<sub>3</sub>M/HP(SiMe<sub>3</sub>)<sub>2</sub> systems, only Me<sub>3</sub>Al gave an isolable adduct, which eliminated CH<sub>4</sub> upon heating to form [Me<sub>2</sub>AlP(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>. Although NMR spectral data indicated adduct formation in the Me<sub>3</sub>Ga and Me<sub>3</sub>In systems, these underwent CH<sub>4</sub> elimination to yield the respective [Me<sub>2</sub>MP(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> species. The variable-temperature, multinuclear NMR study of the Me<sub>2</sub>AlH/P(SiMe<sub>3</sub>)<sub>3</sub> system indicated adduct formation at −90 °C and subsequent conversion to cyclic oligomeric [Me<sub>2</sub>AlP(SiMe<sub>3</sub>)<sub>2</sub>]<i><sub>n</sub></i>[Me<sub>2</sub>AlH]<i><sub>m</sub></i> species at −80 °C that ultimately produced [Me<sub>2</sub>AlP(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>. The reactivity of Bu<sup>i</sup><sub>2</sub>AlH toward P(SiMe<sub>3</sub>)<sub>3</sub> and HP(SiMe<sub>3</sub>)<sub>2</sub> is much slower then that of Me<sub>2</sub>AlH. In the Bu<sup>i</sup><sub>2</sub>AlH/HP(SiMe<sub>3</sub>)<sub>2</sub> system, H<sub>2</sub> elimination is favored and [Bu<sup>i</sup><sub>2</sub>AlP(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> and Bu<sup>i</sup><sub>2</sub>AlP(SiMe<sub>2</sub>)<sub>2</sub>·Bu<sup>i</sup><sub>2</sub>AlP(H)SiMe<sub>3</sub> are formed. An X-ray structure analysis of [Bu<sup>i</sup><sub>2</sub>AlP(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> establishes the planarity of the (AlP)<sub>2</sub> core.