A 4- to 7-membered chelate ring expansion in a Ph₂PCH₂PPh₂(dppm) derivative: X-ray crystal structure of [(OC)₄W{Ph₂PNHNC(Ph)CH₂PPh₂}]

Bis[diphenylphosphino]methane and its bridge-substituted analogues as chemically non-innocent ligands for H2 activation

“…1 While several mononuclear dppm-type complexes have found remarkable applications in homogenous catalysis, 2,3 the chelating dppm ligand(s) are generally considered as spectators with the notable exception of the efficient chirality induction brought by P-chirogenic derivatives. 4 Since the pioneering work of Shaw, 5 it is well known, however, that the CH2 bridge of chelating dppm can be readily deprotonated to generate anionic bis [diphenylphosphino]methanide (dppm − ) scaffold (Scheme 1, (a)). The nucleophilic character of the bridging carbon atom in such species has later been exploited for the preparation of various bridge-functionalized dppm derivatives 5,6 (Scheme 1, (b)) or bi-or polymetallic compounds 7 (Scheme 1, (c)).…”

“…4 Since the pioneering work of Shaw, 5 it is well known, however, that the CH2 bridge of chelating dppm can be readily deprotonated to generate anionic bis [diphenylphosphino]methanide (dppm − ) scaffold (Scheme 1, (a)). The nucleophilic character of the bridging carbon atom in such species has later been exploited for the preparation of various bridge-functionalized dppm derivatives 5,6 (Scheme 1, (b)) or bi-or polymetallic compounds 7 (Scheme 1, (c)). We report herein the first experimental evidence that the deprotonation of dppm-type ligands can also lead to neutral cyclometallated κ 3 P,C,P-diphosphinomethanide Scheme 1.…”

Backbone modified small bite-angle diphosphines: Synthesis and molecular structures of [M(CO)4{X2PC(R1R2)PX2}] (M=Mo, W; X=Ph, Cy; R1=H, Me, Et, Pr, allyl, R2=Me, allyl)

“…This contribution has developed work previously reported by Shaw and co-workers [66][67][68][69][70][71][72], showing that the backbone of the readily available small bite-angle diphosphine dppm can be readily modified when coordinated to the molybdenum and tungsten tetracarbonyl centres. Importantly, asymmetric disubstituted complexes unavailable via standard methods can be prepared in this manner.…”

“…In the early 1980s, Shaw and co-workers developed an on-metal route to the backbone functionalisation of dppm [66][67][68][69][70][71][72]. This utilises the enhanced acidity of the methylene protons upon coordination of the diphosphine to a low-valent metal centre, those with electron-withdrawing ligands being particularly suitable.…”

“…In this way, [Mo(CO) 4 {Ph 2 PCH(Me)PPh 2 }] (2) can be prepared in moderate yields[66], being available in similar amounts…”