Reaction of constrained bicyclic aminophosphines with cyclopentadienyltricarbonylmolybdenum(II) derivatives. Investigations into the basicity of the nitrogen site

Abstract

The donor ability of constrained bicyclic aminophosphane ligands P(OCH2CH2)2N (la) and P(OCMe2CH2)2N (lb) has been evaluated and compared with that of their acyclic analogue (EtO)2PNMe2 (lc) toward a series of CpMo(CO)3X derivatives (X = H, Cl, CH3). A CO group in CpMo(CO)3Cl is readily substituted at room temperature; further substitution requires photochemical activation. Coordination always occurs through P. The i'(CO) frequencies of the adducts indicate a higher 7r-accepting character for the bicyclic ligands than for the nonconstrained analogue. Gaseous HC1 provokes the quaternization of the nitrogen site in HCpMo(CO)2 (lb), which thus displays definite basicity while retaining the P-N bond; in contrast, HC1 cleaves the P-N bond of the adduct of the noncyclic lc. The first stable compound with a protonated P-bound nitrogen could thus be isolated and was fully characterized.

About the Coordination Chemistry of the Phosphorus-Nitrogen Entity

“…When for example the frequency of the v(C0) vibrations of M(CO),L adducts are measured-a commonly used approach to probe the a-accepting ability of a ligand L-one observes that these frequencies are significantly higher than L = 1 than with related but acyclic phosphorus ligands reputed to be strongly Ir-acid (Scheme 17). [22][23][24][25][26][27][28]29 This again is in line with the p,-d, rationale: the overlap of the orbitals concerned being expected to be less effective when nitrogen is pyramidal, the a-acid character of the phosphorus with respect to the metal should be enhanced; but the strain imposed on the angles at phosphorus is also expected to influence this character.…”

Synthesis, protonation sequence, and NMR studies of polyazamacrocyclic methylenephosphonates

“…Similarly, the constrained bicyclic P(OCMe2CH2)2N forms a bis-(borane) adduct. 21,24 In a recent communication,25 we demonstrated conclusively19 the synthesis and characterization of the first known bis(borane) adduct, H3BP(NMe2-BH3)Me2, of an acyclic aminophosphine. Previously, the possibility of the nitrogen atom serving as a donor site in this compound was dismissed.6,15,17 We have now extended this work to establish the generality of N-B bonding and those factors influencing P-B and N-B bonding in acyclic aminophosphine/BH3 reaction systems.…”

The solid-state isomerization of cis- and trans-(η5-C5H4Me)Mo(CO)2(P(OiPr)3)I

“…Since then modification of complexes of this type has been achieved by replacing the ring protons with other substituents or modifying the ligand set (CO, L, X), and this has resulted in the synthesis of many hundreds of complexes of this type [2,3]. Extensive studies of these complexes have included thermal [4][5][6][7][8], photochemical [9,10] and induced [11][12][13] substitution reactions (of CO, L, X), matrix isolation studies [14], isomerization studies [10,15,16], etc. A significant breakthrough in this area of chemistry was the physical separation of the pure cis and trans isomers of (η 5 -C 5 H 5 )Mo(CO) 2 (PPh 3 )I in 1975 [17].…”