Oxidation Products of Calcium and Strontium Bis(diphenylphosphanide)

Abstract

The tetrahydrofuran adducts [(thf)(4)M(PPh(2))(2)] (M = Ca, Sr) are air sensitive and can easily be oxidized by chalcogens. Metalation of diphenylphosphane oxide, diphenylphosphinic acid, and diphenyldithiophosphinic acid as well as salt metathetical approaches of the potassium salts with MI(2) allow the synthesis of [(thf)(4)Ca(OPPh(2))(2)] (1), [(dmso)(2)Ca(O(2)PPh(2))(2)] (2), [(thf)(3)Ca(O(2)PPh(2))I](2) (3), [(thf)(3)Ca(S(2)PPh(2))(2)] (4), [(thf)(2)Ca(Se(2)PPh(2))(2)] (5), [(thf)(3)Sr(S(2)PPh(2))(2)] (6), [(thf)(3)Sr(Se(2)PPh(2))(2)] (7), and [(thf)(2)Ca(O(2)PPh(2))(S(2)PPh(2))](2) (8), respectively. The diphenylphosphinite anion in 1 contains a phosphorus atom in a trigonal pyramidal environment and binds terminally via the oxygen atom to calcium. The diphenylphosphinate anions act as bridging ligands leading to polymeric structures of calcium bis(diphenylphosphinates). Therefore strong Lewis bases such as dimethylsulfoxide (dmso) are required to recrystallize this complex yielding chain-like 2. The chain structure can also be cut into smaller units by ligands which avoid bridging positions such as iodide and diphenyldithiophosphinate (3 and 8, respectively). In general, diphenyldithio- and -diselenophosphinate anions act as terminal ligands and allow the isolation of mononuclear complexes 4 to 7. In these molecules the alkaline earth metals show coordination numbers of six (5) and seven (4, 6, and 7).

Recent Advances in Metal-Catalyzed C–P Bond Formation

“…The proposed mechanism includes insertion of the alkyne into the Ca-P bond and protonolysis of the new Ca-C bond with PHPh 2 to form the product and regenerate the catalyst [34]. Similar chemistry had been observed earlier with ytterbium-phosphido catalysts [35].…”

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

“…A 31 P{ 1 H} NMR spectrum, recorded after a few hours, already showed primarily 2,6-bis(diphenylphosphanylmethyl)benzene. Storage of the reaction solution at −40 °C led to crystallization of [(thf)3Ca(I)(µ-O2PPh2)]2 (3b, Figure 6); a motif of this compound has been reported earlier [29,30]. In analogy to 3a, the central feature is a centrosymmetric eight-membered Ca2P2O4 ring with an average Ca-O distance of 224.3 pm.…”

Catalytic synthesis of vinylphosphanes via calcium-mediated intermolecular hydrophosphanylation of alkynes and butadiynes

“…Therefore, saturated and quadruply hydrophosphanylated butadiynes [yielding 1,4-diorganyl-tetrakis(diphenylphosphanyl)butanes] were not detected. Table 1 Comparison of selected structural data of cis-and trans-1,2-diphenyl-1-diphenylphosphanylethene (2a) [36], cis-1-phenyl-2-diphenylphosphanylethene (A) [34], and cis-1-phenyl-2-diphenylphosphanyl-1-propene (2b). (7) 102.09 (7) 102.77 (7) 101.06 (7) C1eP1eC16 104.35 (7) 105.08 (6) 99.78 (7) 102.67 (7) C10eP1eC16 102.78 (7) 100.39 (6) 98.57 (6) 102.14 (7) Taking these observations into account, a reaction sequence as shown in Scheme 3 can be proposed.…”

“…The allene backbone shows very short C]C double bonds due to the enhanced s-orbital contribution of the middle sphybridyzed carbon atom C3. This allene fragment is nearly linear Table 5 Comparison of selected structural data of the NUPHOS diphosphanes Ph 2 P(R)C] CHeCH]C(R)PPh 2 3 Me (R ¼ Me), 3 Ph (R ¼ Ph) [34], and 3 Silyl (R ¼ SiMe 3 ) with crystallographic inversion symmetry. (C2eC3eC4 177.3 (2) ).…”

“…The use of calcium in catalyst systems tremendously gained on importance with the availability of soluble organocalcium complexes. We already tested the effectivity of [(thf) 4 Ca(PPh 2 ) 2 ] (1) as a catalyst for stereoselective hydrophosphanylation of diphenylbutadiyne with diphenylphosphane [34]. Now we extend our investigations on butadiynes with different substituents such as alkyl, aryl and trialkylsilyl in order to investigate the scope of this heterofunctionalization of these alkynes.…”