36. Trimethylgallium. Part III. Reaction with diphenylphosphine and -arsine

Transition-metal complexes of organoaluminum phosphides. Synthesis, characterization, and crystal and molecular structure of Cr(CO)5(PPh2Al)(CH2SiMe3)2.NMe3

“…The (OC) 5 Cr-P portion of the structure has approximate C4v symmetry, and the (OC) 5 Cr-PPh 2 system lends itself to comparison with parameters obtained for (OC) 5 Cr(PPh 3 ). 15 The equatorial Cr-CO linkages in the The geometry about the tetrahedrally-coordinated phosphorus atom is decidedly irregular: the Cr-P-Al angle is increased to 124.64(4)0, the two Cr-P-C angles are inequlvalent [Cr-P-C(21) a115.00(11)0 and Cr-P-C(1l) *105.99(11)0], the Al-P-C angles are close to equivalent CAl-P-C(11) =104.00(11)0 and A1-P-C(21) = 103.40 (11) The aluminum-alkyl distances (Al:CH 2 SiI~e 3 ) are A1-C(la) -1.963 (4) There was no apparent change in the phenyl region of the spectrum to suggest that the phosphorous was complexing the chromium.…”

“…However, all known compounds of the type R 2 A1PR 2 exist as dimers or trimers 2 ' 3 with coordinatively saturated aluminum and phosphorus atoms. Consequently, a method had to be found to provide an aluminum-phosphorus species which could react as a Lewis base with Cr(CO) 5 . For comparison, the boron compound , PPh 2 B(NMe 2 ) 2 , used to prepare the complex with the Cr-P-B bond sequence, is a monomer and has a basic phosphorus atom.…”

“…However, there is only one previous example of a well-defined compound in which the phosphido group bridges a transition metal and a main-group element moiety. The novel compound Cr(CO) 5 PPh B(NMe m e t a a n aO m a i nh 2 S ( e 2 ) 2 was prepared from Cr(CO) 5 (THF) and PPh 2 B(NMe 2 ) 2 . Since there are no examples of fully characterized compounds in which the phosphido group bridged a transition metal and a main-group organometallic moiety, the goal of our research was the synthesis of a complex with the formula…”

“…A likely path for this reac on involves the initial cleavage of the long P-Al bond. In attempts to find ht~er preparative reactions to compounds with a Cr-P-Al bond sequence, the related reactions of Cr(CO) 5 1 (L =CO, CH CN, TFIF) with R 2 AlPPh 2 (R -Me, Et) were studied but the desired compounds were not formed. Available data suggest that the labile ligand on chromium was attacked by the alLwiinum-phosphorus reagent.…”

Preparation and Properties of Diethyl(diphenylphosphinyl)aluminium

“…Under no conditions could a stable con~plex be isolated. In contrast, Coates and Grahain (17) reported that A I I~~A I -P ( P~)~ \vould coinplex with trimethylarnine (stable to 65') but there was no indication of the stoichioinetry of the product. We did find, however, that acridine would cleave the dimeric forin of I and form a stable conlplex with the monomeric form.…”