Reactivity of R2AlH (R = Me, Bui) and Me3M (M = Al, Ga, In) toward the Silylphosphines P(SiMe3)3 and HP(SiMe3)2

Cyclo-Dipnictadialanes

Using the AlI precursor Cp3t Al in conjunction with triphosphiranes (PAr)3 (Ar=Mes, Dip, Tip) we have succeeded in preparing Lewis base-free cyclic diphosphadialanes with both the Al and P atoms bearing three substituents. Using the sterically more demanding Dip and Tip substituents the first 1,2-diphospha-3,4-dialuminacyclobutanes were obtained, whereas with Mes substituents [Cp3t Al(μ-PMes)]2 is formed. This divergent reactivity was corroborated by DFT studies, which indicated the thermodynamic preference for the 1,2-diphospha-3,4-dialuminacyclobutane form for sterically more demanding groups on phosphorus. Using Cp*Al we could extend this concept to the corresponding cyclic diarsadialanes [Cp*Al(μ-AsAr)]2 (Ar=Dip, Tip) and additionally add the phosphorus variants [Cp*Al(μ-PAr)]2 (P=Mes, Dip, Tip). The reactivity of one variant [Cp3t Al(μ-PPh)]2 towards NHCs was tested and resulted in double NHC-stabilised [Cp3t (IiPr2 )Al(μ-PPh)]2 .

An NHC–phosphinidenyl as a synthon for new group 13/15 compounds

The deprotonated parent phosphinidene SIMesPK (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) was used as a synthon for new group 13/15 cycles and cage compounds such as [SIMesPGatBu₂]₂.

Cyclic NHC-stabilized silylphosphinoalanes and -gallanes

The reaction between prestabilized group 13 metal hydrides and primary silylphosphines lead to the formation of rare, butterfly-like folded, four membered rings including free lone pairs on the phosphorus atoms, wherein the Lewis base can readily be substituted by N-heterocyclic carbenes.

Practical routes to (SiH₃)₃P: applications in group IV semiconductor activation and in group III-V molecular synthesis

The (SiH₃)₃P hydride is introduced as a practical source for n-doping of group IV semiconductors and as a highly-reactive delivery agent of -(SiH₃)₂P functionalities in exploratory synthesis. In contrast to earlier methods, the compound is produced here in high purity quantitative yields via a new single-step method based on reactions of SiH₃Br and (Me₃Sn)₃P, circumventing the need for toxic and unstable starting materials. As an initial demonstration of its utility we synthesized monosubstituted Me₂M-P(SiH₃)₂ (M = Al, Ga, In) derivatives of Me₃M containing the (SiH₃)₂P ligand for the first time, in analogy to the known Me₂M-P(SiMe₃)₂ counterparts. A dimeric structure of Me₂M-P(SiH₃)₂ is proposed on the basis of spectroscopic characterizations and quantum chemical simulations. Next, in the context of materials synthesis, the (SiH₃)₃P compound was used to dope germanium for the first time by building a prototype p(++)Si(100)/i-Ge/n-Ge photodiode structure. The resultant n-type Ge layers contained active carrier concentrations of 3-4 × 10¹⁹ atoms cm⁻³ as determined by spectroscopic ellipsometry and confirmed by SIMS. Strain analysis using high resolution XRD yielded a Si content of 4 × 10²⁰ atoms cm⁻³ in agreement with SIMS and within the range expected for incorporating Si₃P type units into the diamond cubic Ge matrix. Extensive characterizations for structure, morphology and crystallinity indicate that the Si co-dopant plays essentially a passive role and does not compromise the device quality of the host material nor does it fundamentally alter its optical properties.

Dimeric (Tris(tert-butyl)silyl)phosphanyl (Tris(tert-butyl)silyl)phosphanediyl Gallane: A Molecule with a Ga−P−Ga Heteroallyl System

The metathesis reaction of potassium (tris(tert-butyl)silyl)phosphanide with GaCl(3) in a molar ratio of 1:1 leads to the formation of [Cl(2)GaP(H)Si(t)Bu(3)](2) (1) as a mixture of cis and trans isomers with very large (1)J(P,H) and (2)J(P,P) coupling constants. The molecular structure of 1 shows a Ga(2)P(2) cycle with nearly planar coordinated phosphorus atoms under neglection of the hydrogen atoms and Ga-P distances of 239 pm. The reaction of GaCl(3) with 3 equiv of potassium (tris(tert-butyl)silyl)phosphanide as well as the reaction of 1 with 2 equiv of KP(H)Si(t)Bu(3) yields [(t)Bu(3)SiP(H)Ga(mu-PSi(t)Bu(3))](2) (2). The central moiety comprises a four-membered Ga(2)P(2) cycle with one planar P atom and extremely short Ga-P bonds of approximately 226 pm, the other being in a pyramidal environment with an angle sum of 298.4 degrees. The structure of 2 can be described as a GaPGa heteroallyl system which is bonded to a phosphanidyl substituent. This idea and its dependency on the steric demand of the trialkylsilyl groups are investigated by DFT calculations on different isomers of 2.

Reactions of H(3)Al.NMe(3) with E(SiMe(3))(3) (E = P, As). Structural Characterization of the Trimer [H(2)AlP(SiMe(3))(2)](3) and Base-Stabilized Adduct [H(2)AlAs(SiMe(3))(2)].NMe(3) and Their Thermal Decomposition toward Nanocrystalline AlP and AlAs, Respectively

Dehydrosilylation reactions in diethyl ether between H(3)Al.NMe(3) and E(SiMe(3))(3) afforded for E = P a high yield of the trimer [H(2)AlP(SiMe(3))(2)](3) (1), while for E = As a monomeric base-stabilized adduct [H(2)AlAs(SiMe(3))(2)].NMe(3) (2) as well as its degradation solid product were obtained. No reaction occurred for E = N. The single-crystal X-ray structure determination for 1 yielded a planar six-membered ring of alternating four-coordinated Al and P centers. The structural solution for 2 revealed the monomeric unit [H(2)AlAs(SiMe(3))(2)] stabilized by coordination of NMe(3) at the Al site. Pyrolysis of 1 at 450 degrees C promoted further dehydrosilylation and yielded a product which by XRD spectroscopy showed the onset of AlP crystallinity while at 950 degrees C afforded nanocrystalline AlP with 5 nm average particle size. Pyrolysis of 2 at 450 degrees C resulted in the formation of nanocrystalline AlAs with 2 nm average particle size. Under applied pyrolysis conditions for 1 and 2, the target elimination-condensation pathway via dehydrosilylation was accompanied by other decomposition side reactions and retention of some contaminant residues.