Bridging ligands phosphorus

The preparation of similar precursors suitable for the deposition of metal nitrides is analogous to the preparations of phosphorus and arsenic compounds. The initial reaction of metal trialkyls MR3 (M = A1, Ga, In) with amines (NHR 2) results in the formation of oligomeric amido compounds [R2MNR 2] (n = 2 or 3) which eliminate alkanes on thermolysis. The incorporation of a proton as a substituent on the pnictide bridging ligand has been examined, and many compounds of the type [R2MNHR ]2 have been synthesized. The presence of this proton may facilitate /3-elimination, allowing lower deposition temperatures to be used. 

Nitrogen-phosphorus bridging ligands, in tetraosmium carbonyls, 6, 917... 

Monomeric Auu has also been established for unsaturated S-donor ligands such as R2NCS2 and S—C(CN)=(CN)-S , and in the dicarbollyl complex [Au QHn ]2. Most Au" compounds, however, contain metal—metal bonds.43 Good examples are the phosphorus ylide complexes shown in Fig. 18-1-3 (see Section 18-1-10). The cation [ AuCl(dppn) 2]2+ contains a Au11—Au" bond of 2.61 A, unsupported by bridging ligands [dppn = 1, 8-bis-(diphenylphosphino)naphthalene].44... 

The coordination chemistry of compounds containing phosphorus-carbon multiple bonds, such as phosphaalkynes, phosphaalkenes, phos-phaallenes, phosphaalkenyls, and phosphaallyls, has been studied extensively (349,350). The chemistry is dominated by the donor properties of the phosphorus atom, and, as far as we are aware, no examples of bimetallic or trimetallic compounds with bridging ligands which link metal centers by a carbon cr bond and a C=P or C P n bond have been recorded. Once the lone pair on the phosphorus atom is involved in bonding, the unsaturated bond becomes a possible site for further coordination. 

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