aluminum phosphide

[stratosphere]

apparently AlP is available in gas cartriges and tablets (although i believe the tablets are sold only to licensed pest controllers) used for pestacide applications.

this would be useful for prepping such things as PCl3,PBr3 (presumably by reaction with Cl2,Br2) with a perhaps useful byproduct of anhyd. AlCl3 or AlBr3.
i presume it would react with alkyl halides to produce the trialkyl-phosphine and AlX3.
i would also pressume it could somehow be used as a reducing agent.

[Rhodium]

AlP sounds very inert to me, it is isoelectronic with the LED semiconductor GaAs (gallium arsenide) and the "synthetic diamond" BN (boron nitride)

[terbium]

from the Merck Index:

Monograph number: 372
Title: Aluminum Phosphide. 
CAS Registry number: [20859-73-8]
Trade names(s): Celphos (Excel); Phostoxin (Degesch); Quickphos (United Phosphorus). 
Molecular formula: AlP
Molecular weight: 57.96
Composition: Al 46.56%, P 53.44%. 
Literature references: Prepd from red phosphorus and aluminum powder:  White, Bushey, J. Am. Chem. Soc. 66, 1666 (1944); Inorg. Syn. 4, 23 (1953); Montignie, Bull. Soc. Chim. France 1946, 276; from Al and Zn2P3:  Wang et al., J. Inorg. Nucl. Chem. 25, 326 (1963).  Use as insecticidal fumigant:  W. Freyberg, W. Haupt, U.S. pat. 2,117,158 (1938 to Freyberg).
Properties: Dark gray or dark yellow crystals.  Cubic zinc blende structure. Must be protected from moist air since it reacts readily to produce phosphine which is highly toxic.  d415  2.85 (Montignie); d 2.40 (Wang et al.).  Does not melt or decompose thermally at temps up to 1000 deg.  Treatment with water and acid produces phosphine in quantitative yields.
Density: 2.85; 2.40

USE:  Source of phosphine; in semiconductor research; as fumigant.

[stratosphere]

id assume the P in AlP would function as an nucleophile/lewis base.
obviously P is more electronegative then Al, and this would be consistant whith its reaction with water/acid to produce H3P.
i can only conjecture about its reaction with Br2, perhaps attaching Br to a more electronegative species like HOBr would be more sure to produce PBr3, although there would be a high risk of also producing H3P.
Br2 does have quite a propensity to react with bases so perhaps the (Br-)(Br+)-->Br- + BrP reaction would work.